From e757c7dea0f2af48406eb87595fbf9d699946fc9 Mon Sep 17 00:00:00 2001
From: Carl Mastrangelo <notcarl@google.com>
Date: Fri, 19 Oct 2018 14:32:40 -0700
Subject: [PATCH] alts: update alts protos to match grpc-proto

---
 .../alts/internal/HandshakerServiceGrpc.java  |    36 +-
 .../io/grpc/alts/internal/AltsContext.java    |  1670 ++
 .../alts/internal/AltsContextOrBuilder.java   |   177 +
 .../grpc/alts/internal/AltsContextProto.java  |    80 +
 .../io/grpc/alts/internal/Altscontext.java    |  1915 ---
 .../java/io/grpc/alts/internal/Endpoint.java  |   736 +
 .../grpc/alts/internal/EndpointOrBuilder.java |    55 +
 .../grpc/alts/internal/HandshakeProtocol.java |   136 +
 .../io/grpc/alts/internal/Handshaker.java     | 13709 ----------------
 .../grpc/alts/internal/HandshakerProto.java   |   235 +
 .../io/grpc/alts/internal/HandshakerReq.java  |  1213 ++
 .../alts/internal/HandshakerReqOrBuilder.java |    86 +
 .../io/grpc/alts/internal/HandshakerResp.java |  1034 ++
 .../internal/HandshakerRespOrBuilder.java     |    86 +
 .../grpc/alts/internal/HandshakerResult.java  |  1554 ++
 .../internal/HandshakerResultOrBuilder.java   |   142 +
 .../grpc/alts/internal/HandshakerStatus.java  |   618 +
 .../internal/HandshakerStatusOrBuilder.java   |    36 +
 .../java/io/grpc/alts/internal/Identity.java  |  1142 ++
 .../grpc/alts/internal/IdentityOrBuilder.java |   101 +
 .../grpc/alts/internal/NetworkProtocol.java   |   112 +
 .../internal/NextHandshakeMessageReq.java     |   474 +
 .../NextHandshakeMessageReqOrBuilder.java     |    20 +
 .../alts/internal/RpcProtocolVersions.java    |  1377 ++
 .../RpcProtocolVersionsOrBuilder.java         |    59 +
 .../io/grpc/alts/internal/SecurityLevel.java  |   117 +
 .../internal/ServerHandshakeParameters.java   |  1084 ++
 .../ServerHandshakeParametersOrBuilder.java   |    97 +
 .../internal/StartClientHandshakeReq.java     |  2577 +++
 .../StartClientHandshakeReqOrBuilder.java     |   289 +
 .../internal/StartServerHandshakeReq.java     |  1781 ++
 .../StartServerHandshakeReqOrBuilder.java     |   213 +
 .../internal/TransportSecurityCommon.java     |  1612 --
 .../TransportSecurityCommonProto.java         |    76 +
 .../grpc/alts/internal/AltsAuthContext.java   |     8 +-
 .../grpc/alts/internal/AltsClientOptions.java |     1 -
 .../alts/internal/AltsHandshakerClient.java   |     9 -
 .../alts/internal/AltsHandshakerOptions.java  |     1 -
 .../alts/internal/AltsHandshakerStub.java     |     2 -
 .../internal/RpcProtocolVersionsUtil.java     |     3 +-
 .../src/main/proto/grpc/gcp/altscontext.proto |     7 +
 alts/src/main/proto/grpc/gcp/handshaker.proto |    10 +-
 .../grpc/gcp/transport_security_common.proto  |     7 +
 .../alts/internal/AltsAuthContextTest.java    |     4 -
 .../alts/internal/AltsClientOptionsTest.java  |     1 -
 .../internal/AltsHandshakerClientTest.java    |     5 -
 .../internal/AltsHandshakerOptionsTest.java   |     1 -
 .../alts/internal/AltsHandshakerStubTest.java |     3 -
 .../internal/AltsProtocolNegotiatorTest.java  |     1 -
 .../alts/internal/AltsTsiHandshakerTest.java  |     3 -
 .../io/grpc/alts/internal/AltsTsiTest.java    |     3 -
 .../alts/internal/MockAltsHandshakerResp.java |     4 -
 .../internal/RpcProtocolVersionsUtilTest.java |     3 +-
 53 files changed, 17424 insertions(+), 17301 deletions(-)
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/AltsContext.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/AltsContextOrBuilder.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/AltsContextProto.java
 delete mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/Altscontext.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/Endpoint.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/EndpointOrBuilder.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/HandshakeProtocol.java
 delete mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/Handshaker.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/HandshakerProto.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/HandshakerReq.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/HandshakerReqOrBuilder.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/HandshakerResp.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/HandshakerRespOrBuilder.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/HandshakerResult.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/HandshakerResultOrBuilder.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/HandshakerStatus.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/HandshakerStatusOrBuilder.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/Identity.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/IdentityOrBuilder.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/NetworkProtocol.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/NextHandshakeMessageReq.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/NextHandshakeMessageReqOrBuilder.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/RpcProtocolVersions.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/RpcProtocolVersionsOrBuilder.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/SecurityLevel.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/ServerHandshakeParameters.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/ServerHandshakeParametersOrBuilder.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/StartClientHandshakeReq.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/StartClientHandshakeReqOrBuilder.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/StartServerHandshakeReq.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/StartServerHandshakeReqOrBuilder.java
 delete mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/TransportSecurityCommon.java
 create mode 100644 alts/src/generated/main/java/io/grpc/alts/internal/TransportSecurityCommonProto.java

diff --git a/alts/src/generated/main/grpc/io/grpc/alts/internal/HandshakerServiceGrpc.java b/alts/src/generated/main/grpc/io/grpc/alts/internal/HandshakerServiceGrpc.java
index 012748d110..79643affaf 100644
--- a/alts/src/generated/main/grpc/io/grpc/alts/internal/HandshakerServiceGrpc.java
+++ b/alts/src/generated/main/grpc/io/grpc/alts/internal/HandshakerServiceGrpc.java
@@ -27,30 +27,30 @@ public final class HandshakerServiceGrpc {
   public static final String SERVICE_NAME = "grpc.gcp.HandshakerService";
 
   // Static method descriptors that strictly reflect the proto.
-  private static volatile io.grpc.MethodDescriptor<io.grpc.alts.internal.Handshaker.HandshakerReq,
-      io.grpc.alts.internal.Handshaker.HandshakerResp> getDoHandshakeMethod;
+  private static volatile io.grpc.MethodDescriptor<io.grpc.alts.internal.HandshakerReq,
+      io.grpc.alts.internal.HandshakerResp> getDoHandshakeMethod;
 
   @io.grpc.stub.annotations.RpcMethod(
       fullMethodName = SERVICE_NAME + '/' + "DoHandshake",
-      requestType = io.grpc.alts.internal.Handshaker.HandshakerReq.class,
-      responseType = io.grpc.alts.internal.Handshaker.HandshakerResp.class,
+      requestType = io.grpc.alts.internal.HandshakerReq.class,
+      responseType = io.grpc.alts.internal.HandshakerResp.class,
       methodType = io.grpc.MethodDescriptor.MethodType.BIDI_STREAMING)
-  public static io.grpc.MethodDescriptor<io.grpc.alts.internal.Handshaker.HandshakerReq,
-      io.grpc.alts.internal.Handshaker.HandshakerResp> getDoHandshakeMethod() {
-    io.grpc.MethodDescriptor<io.grpc.alts.internal.Handshaker.HandshakerReq, io.grpc.alts.internal.Handshaker.HandshakerResp> getDoHandshakeMethod;
+  public static io.grpc.MethodDescriptor<io.grpc.alts.internal.HandshakerReq,
+      io.grpc.alts.internal.HandshakerResp> getDoHandshakeMethod() {
+    io.grpc.MethodDescriptor<io.grpc.alts.internal.HandshakerReq, io.grpc.alts.internal.HandshakerResp> getDoHandshakeMethod;
     if ((getDoHandshakeMethod = HandshakerServiceGrpc.getDoHandshakeMethod) == null) {
       synchronized (HandshakerServiceGrpc.class) {
         if ((getDoHandshakeMethod = HandshakerServiceGrpc.getDoHandshakeMethod) == null) {
           HandshakerServiceGrpc.getDoHandshakeMethod = getDoHandshakeMethod = 
-              io.grpc.MethodDescriptor.<io.grpc.alts.internal.Handshaker.HandshakerReq, io.grpc.alts.internal.Handshaker.HandshakerResp>newBuilder()
+              io.grpc.MethodDescriptor.<io.grpc.alts.internal.HandshakerReq, io.grpc.alts.internal.HandshakerResp>newBuilder()
               .setType(io.grpc.MethodDescriptor.MethodType.BIDI_STREAMING)
               .setFullMethodName(generateFullMethodName(
                   "grpc.gcp.HandshakerService", "DoHandshake"))
               .setSampledToLocalTracing(true)
               .setRequestMarshaller(io.grpc.protobuf.ProtoUtils.marshaller(
-                  io.grpc.alts.internal.Handshaker.HandshakerReq.getDefaultInstance()))
+                  io.grpc.alts.internal.HandshakerReq.getDefaultInstance()))
               .setResponseMarshaller(io.grpc.protobuf.ProtoUtils.marshaller(
-                  io.grpc.alts.internal.Handshaker.HandshakerResp.getDefaultInstance()))
+                  io.grpc.alts.internal.HandshakerResp.getDefaultInstance()))
                   .setSchemaDescriptor(new HandshakerServiceMethodDescriptorSupplier("DoHandshake"))
                   .build();
           }
@@ -96,8 +96,8 @@ public final class HandshakerServiceGrpc {
      * response before sending next request.
      * </pre>
      */
-    public io.grpc.stub.StreamObserver<io.grpc.alts.internal.Handshaker.HandshakerReq> doHandshake(
-        io.grpc.stub.StreamObserver<io.grpc.alts.internal.Handshaker.HandshakerResp> responseObserver) {
+    public io.grpc.stub.StreamObserver<io.grpc.alts.internal.HandshakerReq> doHandshake(
+        io.grpc.stub.StreamObserver<io.grpc.alts.internal.HandshakerResp> responseObserver) {
       return asyncUnimplementedStreamingCall(getDoHandshakeMethod(), responseObserver);
     }
 
@@ -107,8 +107,8 @@ public final class HandshakerServiceGrpc {
             getDoHandshakeMethod(),
             asyncBidiStreamingCall(
               new MethodHandlers<
-                io.grpc.alts.internal.Handshaker.HandshakerReq,
-                io.grpc.alts.internal.Handshaker.HandshakerResp>(
+                io.grpc.alts.internal.HandshakerReq,
+                io.grpc.alts.internal.HandshakerResp>(
                   this, METHODID_DO_HANDSHAKE)))
           .build();
     }
@@ -142,8 +142,8 @@ public final class HandshakerServiceGrpc {
      * response before sending next request.
      * </pre>
      */
-    public io.grpc.stub.StreamObserver<io.grpc.alts.internal.Handshaker.HandshakerReq> doHandshake(
-        io.grpc.stub.StreamObserver<io.grpc.alts.internal.Handshaker.HandshakerResp> responseObserver) {
+    public io.grpc.stub.StreamObserver<io.grpc.alts.internal.HandshakerReq> doHandshake(
+        io.grpc.stub.StreamObserver<io.grpc.alts.internal.HandshakerResp> responseObserver) {
       return asyncBidiStreamingCall(
           getChannel().newCall(getDoHandshakeMethod(), getCallOptions()), responseObserver);
     }
@@ -218,7 +218,7 @@ public final class HandshakerServiceGrpc {
       switch (methodId) {
         case METHODID_DO_HANDSHAKE:
           return (io.grpc.stub.StreamObserver<Req>) serviceImpl.doHandshake(
-              (io.grpc.stub.StreamObserver<io.grpc.alts.internal.Handshaker.HandshakerResp>) responseObserver);
+              (io.grpc.stub.StreamObserver<io.grpc.alts.internal.HandshakerResp>) responseObserver);
         default:
           throw new AssertionError();
       }
@@ -231,7 +231,7 @@ public final class HandshakerServiceGrpc {
 
     @java.lang.Override
     public com.google.protobuf.Descriptors.FileDescriptor getFileDescriptor() {
-      return io.grpc.alts.internal.Handshaker.getDescriptor();
+      return io.grpc.alts.internal.HandshakerProto.getDescriptor();
     }
 
     @java.lang.Override
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/AltsContext.java b/alts/src/generated/main/java/io/grpc/alts/internal/AltsContext.java
new file mode 100644
index 0000000000..b8dbb7b1a5
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/AltsContext.java
@@ -0,0 +1,1670 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/altscontext.proto
+
+package io.grpc.alts.internal;
+
+/**
+ * Protobuf type {@code grpc.gcp.AltsContext}
+ */
+public  final class AltsContext extends
+    com.google.protobuf.GeneratedMessageV3 implements
+    // @@protoc_insertion_point(message_implements:grpc.gcp.AltsContext)
+    AltsContextOrBuilder {
+private static final long serialVersionUID = 0L;
+  // Use AltsContext.newBuilder() to construct.
+  private AltsContext(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
+    super(builder);
+  }
+  private AltsContext() {
+    applicationProtocol_ = "";
+    recordProtocol_ = "";
+    securityLevel_ = 0;
+    peerServiceAccount_ = "";
+    localServiceAccount_ = "";
+  }
+
+  @java.lang.Override
+  public final com.google.protobuf.UnknownFieldSet
+  getUnknownFields() {
+    return this.unknownFields;
+  }
+  private AltsContext(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    this();
+    if (extensionRegistry == null) {
+      throw new java.lang.NullPointerException();
+    }
+    int mutable_bitField0_ = 0;
+    com.google.protobuf.UnknownFieldSet.Builder unknownFields =
+        com.google.protobuf.UnknownFieldSet.newBuilder();
+    try {
+      boolean done = false;
+      while (!done) {
+        int tag = input.readTag();
+        switch (tag) {
+          case 0:
+            done = true;
+            break;
+          default: {
+            if (!parseUnknownFieldProto3(
+                input, unknownFields, extensionRegistry, tag)) {
+              done = true;
+            }
+            break;
+          }
+          case 10: {
+            java.lang.String s = input.readStringRequireUtf8();
+
+            applicationProtocol_ = s;
+            break;
+          }
+          case 18: {
+            java.lang.String s = input.readStringRequireUtf8();
+
+            recordProtocol_ = s;
+            break;
+          }
+          case 24: {
+            int rawValue = input.readEnum();
+
+            securityLevel_ = rawValue;
+            break;
+          }
+          case 34: {
+            java.lang.String s = input.readStringRequireUtf8();
+
+            peerServiceAccount_ = s;
+            break;
+          }
+          case 42: {
+            java.lang.String s = input.readStringRequireUtf8();
+
+            localServiceAccount_ = s;
+            break;
+          }
+          case 50: {
+            io.grpc.alts.internal.RpcProtocolVersions.Builder subBuilder = null;
+            if (peerRpcVersions_ != null) {
+              subBuilder = peerRpcVersions_.toBuilder();
+            }
+            peerRpcVersions_ = input.readMessage(io.grpc.alts.internal.RpcProtocolVersions.parser(), extensionRegistry);
+            if (subBuilder != null) {
+              subBuilder.mergeFrom(peerRpcVersions_);
+              peerRpcVersions_ = subBuilder.buildPartial();
+            }
+
+            break;
+          }
+          case 58: {
+            if (!((mutable_bitField0_ & 0x00000040) == 0x00000040)) {
+              peerAttributes_ = com.google.protobuf.MapField.newMapField(
+                  PeerAttributesDefaultEntryHolder.defaultEntry);
+              mutable_bitField0_ |= 0x00000040;
+            }
+            com.google.protobuf.MapEntry<java.lang.String, java.lang.String>
+            peerAttributes__ = input.readMessage(
+                PeerAttributesDefaultEntryHolder.defaultEntry.getParserForType(), extensionRegistry);
+            peerAttributes_.getMutableMap().put(
+                peerAttributes__.getKey(), peerAttributes__.getValue());
+            break;
+          }
+        }
+      }
+    } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+      throw e.setUnfinishedMessage(this);
+    } catch (java.io.IOException e) {
+      throw new com.google.protobuf.InvalidProtocolBufferException(
+          e).setUnfinishedMessage(this);
+    } finally {
+      this.unknownFields = unknownFields.build();
+      makeExtensionsImmutable();
+    }
+  }
+  public static final com.google.protobuf.Descriptors.Descriptor
+      getDescriptor() {
+    return io.grpc.alts.internal.AltsContextProto.internal_static_grpc_gcp_AltsContext_descriptor;
+  }
+
+  @SuppressWarnings({"rawtypes"})
+  protected com.google.protobuf.MapField internalGetMapField(
+      int number) {
+    switch (number) {
+      case 7:
+        return internalGetPeerAttributes();
+      default:
+        throw new RuntimeException(
+            "Invalid map field number: " + number);
+    }
+  }
+  protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internalGetFieldAccessorTable() {
+    return io.grpc.alts.internal.AltsContextProto.internal_static_grpc_gcp_AltsContext_fieldAccessorTable
+        .ensureFieldAccessorsInitialized(
+            io.grpc.alts.internal.AltsContext.class, io.grpc.alts.internal.AltsContext.Builder.class);
+  }
+
+  private int bitField0_;
+  public static final int APPLICATION_PROTOCOL_FIELD_NUMBER = 1;
+  private volatile java.lang.Object applicationProtocol_;
+  /**
+   * <pre>
+   * The application protocol negotiated for this connection.
+   * </pre>
+   *
+   * <code>string application_protocol = 1;</code>
+   */
+  public java.lang.String getApplicationProtocol() {
+    java.lang.Object ref = applicationProtocol_;
+    if (ref instanceof java.lang.String) {
+      return (java.lang.String) ref;
+    } else {
+      com.google.protobuf.ByteString bs = 
+          (com.google.protobuf.ByteString) ref;
+      java.lang.String s = bs.toStringUtf8();
+      applicationProtocol_ = s;
+      return s;
+    }
+  }
+  /**
+   * <pre>
+   * The application protocol negotiated for this connection.
+   * </pre>
+   *
+   * <code>string application_protocol = 1;</code>
+   */
+  public com.google.protobuf.ByteString
+      getApplicationProtocolBytes() {
+    java.lang.Object ref = applicationProtocol_;
+    if (ref instanceof java.lang.String) {
+      com.google.protobuf.ByteString b = 
+          com.google.protobuf.ByteString.copyFromUtf8(
+              (java.lang.String) ref);
+      applicationProtocol_ = b;
+      return b;
+    } else {
+      return (com.google.protobuf.ByteString) ref;
+    }
+  }
+
+  public static final int RECORD_PROTOCOL_FIELD_NUMBER = 2;
+  private volatile java.lang.Object recordProtocol_;
+  /**
+   * <pre>
+   * The record protocol negotiated for this connection.
+   * </pre>
+   *
+   * <code>string record_protocol = 2;</code>
+   */
+  public java.lang.String getRecordProtocol() {
+    java.lang.Object ref = recordProtocol_;
+    if (ref instanceof java.lang.String) {
+      return (java.lang.String) ref;
+    } else {
+      com.google.protobuf.ByteString bs = 
+          (com.google.protobuf.ByteString) ref;
+      java.lang.String s = bs.toStringUtf8();
+      recordProtocol_ = s;
+      return s;
+    }
+  }
+  /**
+   * <pre>
+   * The record protocol negotiated for this connection.
+   * </pre>
+   *
+   * <code>string record_protocol = 2;</code>
+   */
+  public com.google.protobuf.ByteString
+      getRecordProtocolBytes() {
+    java.lang.Object ref = recordProtocol_;
+    if (ref instanceof java.lang.String) {
+      com.google.protobuf.ByteString b = 
+          com.google.protobuf.ByteString.copyFromUtf8(
+              (java.lang.String) ref);
+      recordProtocol_ = b;
+      return b;
+    } else {
+      return (com.google.protobuf.ByteString) ref;
+    }
+  }
+
+  public static final int SECURITY_LEVEL_FIELD_NUMBER = 3;
+  private int securityLevel_;
+  /**
+   * <pre>
+   * The security level of the created secure channel.
+   * </pre>
+   *
+   * <code>.grpc.gcp.SecurityLevel security_level = 3;</code>
+   */
+  public int getSecurityLevelValue() {
+    return securityLevel_;
+  }
+  /**
+   * <pre>
+   * The security level of the created secure channel.
+   * </pre>
+   *
+   * <code>.grpc.gcp.SecurityLevel security_level = 3;</code>
+   */
+  public io.grpc.alts.internal.SecurityLevel getSecurityLevel() {
+    io.grpc.alts.internal.SecurityLevel result = io.grpc.alts.internal.SecurityLevel.valueOf(securityLevel_);
+    return result == null ? io.grpc.alts.internal.SecurityLevel.UNRECOGNIZED : result;
+  }
+
+  public static final int PEER_SERVICE_ACCOUNT_FIELD_NUMBER = 4;
+  private volatile java.lang.Object peerServiceAccount_;
+  /**
+   * <pre>
+   * The peer service account.
+   * </pre>
+   *
+   * <code>string peer_service_account = 4;</code>
+   */
+  public java.lang.String getPeerServiceAccount() {
+    java.lang.Object ref = peerServiceAccount_;
+    if (ref instanceof java.lang.String) {
+      return (java.lang.String) ref;
+    } else {
+      com.google.protobuf.ByteString bs = 
+          (com.google.protobuf.ByteString) ref;
+      java.lang.String s = bs.toStringUtf8();
+      peerServiceAccount_ = s;
+      return s;
+    }
+  }
+  /**
+   * <pre>
+   * The peer service account.
+   * </pre>
+   *
+   * <code>string peer_service_account = 4;</code>
+   */
+  public com.google.protobuf.ByteString
+      getPeerServiceAccountBytes() {
+    java.lang.Object ref = peerServiceAccount_;
+    if (ref instanceof java.lang.String) {
+      com.google.protobuf.ByteString b = 
+          com.google.protobuf.ByteString.copyFromUtf8(
+              (java.lang.String) ref);
+      peerServiceAccount_ = b;
+      return b;
+    } else {
+      return (com.google.protobuf.ByteString) ref;
+    }
+  }
+
+  public static final int LOCAL_SERVICE_ACCOUNT_FIELD_NUMBER = 5;
+  private volatile java.lang.Object localServiceAccount_;
+  /**
+   * <pre>
+   * The local service account.
+   * </pre>
+   *
+   * <code>string local_service_account = 5;</code>
+   */
+  public java.lang.String getLocalServiceAccount() {
+    java.lang.Object ref = localServiceAccount_;
+    if (ref instanceof java.lang.String) {
+      return (java.lang.String) ref;
+    } else {
+      com.google.protobuf.ByteString bs = 
+          (com.google.protobuf.ByteString) ref;
+      java.lang.String s = bs.toStringUtf8();
+      localServiceAccount_ = s;
+      return s;
+    }
+  }
+  /**
+   * <pre>
+   * The local service account.
+   * </pre>
+   *
+   * <code>string local_service_account = 5;</code>
+   */
+  public com.google.protobuf.ByteString
+      getLocalServiceAccountBytes() {
+    java.lang.Object ref = localServiceAccount_;
+    if (ref instanceof java.lang.String) {
+      com.google.protobuf.ByteString b = 
+          com.google.protobuf.ByteString.copyFromUtf8(
+              (java.lang.String) ref);
+      localServiceAccount_ = b;
+      return b;
+    } else {
+      return (com.google.protobuf.ByteString) ref;
+    }
+  }
+
+  public static final int PEER_RPC_VERSIONS_FIELD_NUMBER = 6;
+  private io.grpc.alts.internal.RpcProtocolVersions peerRpcVersions_;
+  /**
+   * <pre>
+   * The RPC protocol versions supported by the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
+   */
+  public boolean hasPeerRpcVersions() {
+    return peerRpcVersions_ != null;
+  }
+  /**
+   * <pre>
+   * The RPC protocol versions supported by the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
+   */
+  public io.grpc.alts.internal.RpcProtocolVersions getPeerRpcVersions() {
+    return peerRpcVersions_ == null ? io.grpc.alts.internal.RpcProtocolVersions.getDefaultInstance() : peerRpcVersions_;
+  }
+  /**
+   * <pre>
+   * The RPC protocol versions supported by the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
+   */
+  public io.grpc.alts.internal.RpcProtocolVersionsOrBuilder getPeerRpcVersionsOrBuilder() {
+    return getPeerRpcVersions();
+  }
+
+  public static final int PEER_ATTRIBUTES_FIELD_NUMBER = 7;
+  private static final class PeerAttributesDefaultEntryHolder {
+    static final com.google.protobuf.MapEntry<
+        java.lang.String, java.lang.String> defaultEntry =
+            com.google.protobuf.MapEntry
+            .<java.lang.String, java.lang.String>newDefaultInstance(
+                io.grpc.alts.internal.AltsContextProto.internal_static_grpc_gcp_AltsContext_PeerAttributesEntry_descriptor, 
+                com.google.protobuf.WireFormat.FieldType.STRING,
+                "",
+                com.google.protobuf.WireFormat.FieldType.STRING,
+                "");
+  }
+  private com.google.protobuf.MapField<
+      java.lang.String, java.lang.String> peerAttributes_;
+  private com.google.protobuf.MapField<java.lang.String, java.lang.String>
+  internalGetPeerAttributes() {
+    if (peerAttributes_ == null) {
+      return com.google.protobuf.MapField.emptyMapField(
+          PeerAttributesDefaultEntryHolder.defaultEntry);
+    }
+    return peerAttributes_;
+  }
+
+  public int getPeerAttributesCount() {
+    return internalGetPeerAttributes().getMap().size();
+  }
+  /**
+   * <pre>
+   * Additional attributes of the peer.
+   * </pre>
+   *
+   * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
+   */
+
+  public boolean containsPeerAttributes(
+      java.lang.String key) {
+    if (key == null) { throw new java.lang.NullPointerException(); }
+    return internalGetPeerAttributes().getMap().containsKey(key);
+  }
+  /**
+   * Use {@link #getPeerAttributesMap()} instead.
+   */
+  @java.lang.Deprecated
+  public java.util.Map<java.lang.String, java.lang.String> getPeerAttributes() {
+    return getPeerAttributesMap();
+  }
+  /**
+   * <pre>
+   * Additional attributes of the peer.
+   * </pre>
+   *
+   * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
+   */
+
+  public java.util.Map<java.lang.String, java.lang.String> getPeerAttributesMap() {
+    return internalGetPeerAttributes().getMap();
+  }
+  /**
+   * <pre>
+   * Additional attributes of the peer.
+   * </pre>
+   *
+   * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
+   */
+
+  public java.lang.String getPeerAttributesOrDefault(
+      java.lang.String key,
+      java.lang.String defaultValue) {
+    if (key == null) { throw new java.lang.NullPointerException(); }
+    java.util.Map<java.lang.String, java.lang.String> map =
+        internalGetPeerAttributes().getMap();
+    return map.containsKey(key) ? map.get(key) : defaultValue;
+  }
+  /**
+   * <pre>
+   * Additional attributes of the peer.
+   * </pre>
+   *
+   * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
+   */
+
+  public java.lang.String getPeerAttributesOrThrow(
+      java.lang.String key) {
+    if (key == null) { throw new java.lang.NullPointerException(); }
+    java.util.Map<java.lang.String, java.lang.String> map =
+        internalGetPeerAttributes().getMap();
+    if (!map.containsKey(key)) {
+      throw new java.lang.IllegalArgumentException();
+    }
+    return map.get(key);
+  }
+
+  private byte memoizedIsInitialized = -1;
+  public final boolean isInitialized() {
+    byte isInitialized = memoizedIsInitialized;
+    if (isInitialized == 1) return true;
+    if (isInitialized == 0) return false;
+
+    memoizedIsInitialized = 1;
+    return true;
+  }
+
+  public void writeTo(com.google.protobuf.CodedOutputStream output)
+                      throws java.io.IOException {
+    if (!getApplicationProtocolBytes().isEmpty()) {
+      com.google.protobuf.GeneratedMessageV3.writeString(output, 1, applicationProtocol_);
+    }
+    if (!getRecordProtocolBytes().isEmpty()) {
+      com.google.protobuf.GeneratedMessageV3.writeString(output, 2, recordProtocol_);
+    }
+    if (securityLevel_ != io.grpc.alts.internal.SecurityLevel.SECURITY_NONE.getNumber()) {
+      output.writeEnum(3, securityLevel_);
+    }
+    if (!getPeerServiceAccountBytes().isEmpty()) {
+      com.google.protobuf.GeneratedMessageV3.writeString(output, 4, peerServiceAccount_);
+    }
+    if (!getLocalServiceAccountBytes().isEmpty()) {
+      com.google.protobuf.GeneratedMessageV3.writeString(output, 5, localServiceAccount_);
+    }
+    if (peerRpcVersions_ != null) {
+      output.writeMessage(6, getPeerRpcVersions());
+    }
+    com.google.protobuf.GeneratedMessageV3
+      .serializeStringMapTo(
+        output,
+        internalGetPeerAttributes(),
+        PeerAttributesDefaultEntryHolder.defaultEntry,
+        7);
+    unknownFields.writeTo(output);
+  }
+
+  public int getSerializedSize() {
+    int size = memoizedSize;
+    if (size != -1) return size;
+
+    size = 0;
+    if (!getApplicationProtocolBytes().isEmpty()) {
+      size += com.google.protobuf.GeneratedMessageV3.computeStringSize(1, applicationProtocol_);
+    }
+    if (!getRecordProtocolBytes().isEmpty()) {
+      size += com.google.protobuf.GeneratedMessageV3.computeStringSize(2, recordProtocol_);
+    }
+    if (securityLevel_ != io.grpc.alts.internal.SecurityLevel.SECURITY_NONE.getNumber()) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeEnumSize(3, securityLevel_);
+    }
+    if (!getPeerServiceAccountBytes().isEmpty()) {
+      size += com.google.protobuf.GeneratedMessageV3.computeStringSize(4, peerServiceAccount_);
+    }
+    if (!getLocalServiceAccountBytes().isEmpty()) {
+      size += com.google.protobuf.GeneratedMessageV3.computeStringSize(5, localServiceAccount_);
+    }
+    if (peerRpcVersions_ != null) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeMessageSize(6, getPeerRpcVersions());
+    }
+    for (java.util.Map.Entry<java.lang.String, java.lang.String> entry
+         : internalGetPeerAttributes().getMap().entrySet()) {
+      com.google.protobuf.MapEntry<java.lang.String, java.lang.String>
+      peerAttributes__ = PeerAttributesDefaultEntryHolder.defaultEntry.newBuilderForType()
+          .setKey(entry.getKey())
+          .setValue(entry.getValue())
+          .build();
+      size += com.google.protobuf.CodedOutputStream
+          .computeMessageSize(7, peerAttributes__);
+    }
+    size += unknownFields.getSerializedSize();
+    memoizedSize = size;
+    return size;
+  }
+
+  @java.lang.Override
+  public boolean equals(final java.lang.Object obj) {
+    if (obj == this) {
+     return true;
+    }
+    if (!(obj instanceof io.grpc.alts.internal.AltsContext)) {
+      return super.equals(obj);
+    }
+    io.grpc.alts.internal.AltsContext other = (io.grpc.alts.internal.AltsContext) obj;
+
+    boolean result = true;
+    result = result && getApplicationProtocol()
+        .equals(other.getApplicationProtocol());
+    result = result && getRecordProtocol()
+        .equals(other.getRecordProtocol());
+    result = result && securityLevel_ == other.securityLevel_;
+    result = result && getPeerServiceAccount()
+        .equals(other.getPeerServiceAccount());
+    result = result && getLocalServiceAccount()
+        .equals(other.getLocalServiceAccount());
+    result = result && (hasPeerRpcVersions() == other.hasPeerRpcVersions());
+    if (hasPeerRpcVersions()) {
+      result = result && getPeerRpcVersions()
+          .equals(other.getPeerRpcVersions());
+    }
+    result = result && internalGetPeerAttributes().equals(
+        other.internalGetPeerAttributes());
+    result = result && unknownFields.equals(other.unknownFields);
+    return result;
+  }
+
+  @java.lang.Override
+  public int hashCode() {
+    if (memoizedHashCode != 0) {
+      return memoizedHashCode;
+    }
+    int hash = 41;
+    hash = (19 * hash) + getDescriptor().hashCode();
+    hash = (37 * hash) + APPLICATION_PROTOCOL_FIELD_NUMBER;
+    hash = (53 * hash) + getApplicationProtocol().hashCode();
+    hash = (37 * hash) + RECORD_PROTOCOL_FIELD_NUMBER;
+    hash = (53 * hash) + getRecordProtocol().hashCode();
+    hash = (37 * hash) + SECURITY_LEVEL_FIELD_NUMBER;
+    hash = (53 * hash) + securityLevel_;
+    hash = (37 * hash) + PEER_SERVICE_ACCOUNT_FIELD_NUMBER;
+    hash = (53 * hash) + getPeerServiceAccount().hashCode();
+    hash = (37 * hash) + LOCAL_SERVICE_ACCOUNT_FIELD_NUMBER;
+    hash = (53 * hash) + getLocalServiceAccount().hashCode();
+    if (hasPeerRpcVersions()) {
+      hash = (37 * hash) + PEER_RPC_VERSIONS_FIELD_NUMBER;
+      hash = (53 * hash) + getPeerRpcVersions().hashCode();
+    }
+    if (!internalGetPeerAttributes().getMap().isEmpty()) {
+      hash = (37 * hash) + PEER_ATTRIBUTES_FIELD_NUMBER;
+      hash = (53 * hash) + internalGetPeerAttributes().hashCode();
+    }
+    hash = (29 * hash) + unknownFields.hashCode();
+    memoizedHashCode = hash;
+    return hash;
+  }
+
+  public static io.grpc.alts.internal.AltsContext parseFrom(
+      java.nio.ByteBuffer data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.AltsContext parseFrom(
+      java.nio.ByteBuffer data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.AltsContext parseFrom(
+      com.google.protobuf.ByteString data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.AltsContext parseFrom(
+      com.google.protobuf.ByteString data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.AltsContext parseFrom(byte[] data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.AltsContext parseFrom(
+      byte[] data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.AltsContext parseFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.AltsContext parseFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.AltsContext parseDelimitedFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.AltsContext parseDelimitedFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.AltsContext parseFrom(
+      com.google.protobuf.CodedInputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.AltsContext parseFrom(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+
+  public Builder newBuilderForType() { return newBuilder(); }
+  public static Builder newBuilder() {
+    return DEFAULT_INSTANCE.toBuilder();
+  }
+  public static Builder newBuilder(io.grpc.alts.internal.AltsContext prototype) {
+    return DEFAULT_INSTANCE.toBuilder().mergeFrom(prototype);
+  }
+  public Builder toBuilder() {
+    return this == DEFAULT_INSTANCE
+        ? new Builder() : new Builder().mergeFrom(this);
+  }
+
+  @java.lang.Override
+  protected Builder newBuilderForType(
+      com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+    Builder builder = new Builder(parent);
+    return builder;
+  }
+  /**
+   * Protobuf type {@code grpc.gcp.AltsContext}
+   */
+  public static final class Builder extends
+      com.google.protobuf.GeneratedMessageV3.Builder<Builder> implements
+      // @@protoc_insertion_point(builder_implements:grpc.gcp.AltsContext)
+      io.grpc.alts.internal.AltsContextOrBuilder {
+    public static final com.google.protobuf.Descriptors.Descriptor
+        getDescriptor() {
+      return io.grpc.alts.internal.AltsContextProto.internal_static_grpc_gcp_AltsContext_descriptor;
+    }
+
+    @SuppressWarnings({"rawtypes"})
+    protected com.google.protobuf.MapField internalGetMapField(
+        int number) {
+      switch (number) {
+        case 7:
+          return internalGetPeerAttributes();
+        default:
+          throw new RuntimeException(
+              "Invalid map field number: " + number);
+      }
+    }
+    @SuppressWarnings({"rawtypes"})
+    protected com.google.protobuf.MapField internalGetMutableMapField(
+        int number) {
+      switch (number) {
+        case 7:
+          return internalGetMutablePeerAttributes();
+        default:
+          throw new RuntimeException(
+              "Invalid map field number: " + number);
+      }
+    }
+    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+        internalGetFieldAccessorTable() {
+      return io.grpc.alts.internal.AltsContextProto.internal_static_grpc_gcp_AltsContext_fieldAccessorTable
+          .ensureFieldAccessorsInitialized(
+              io.grpc.alts.internal.AltsContext.class, io.grpc.alts.internal.AltsContext.Builder.class);
+    }
+
+    // Construct using io.grpc.alts.internal.AltsContext.newBuilder()
+    private Builder() {
+      maybeForceBuilderInitialization();
+    }
+
+    private Builder(
+        com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+      super(parent);
+      maybeForceBuilderInitialization();
+    }
+    private void maybeForceBuilderInitialization() {
+      if (com.google.protobuf.GeneratedMessageV3
+              .alwaysUseFieldBuilders) {
+      }
+    }
+    public Builder clear() {
+      super.clear();
+      applicationProtocol_ = "";
+
+      recordProtocol_ = "";
+
+      securityLevel_ = 0;
+
+      peerServiceAccount_ = "";
+
+      localServiceAccount_ = "";
+
+      if (peerRpcVersionsBuilder_ == null) {
+        peerRpcVersions_ = null;
+      } else {
+        peerRpcVersions_ = null;
+        peerRpcVersionsBuilder_ = null;
+      }
+      internalGetMutablePeerAttributes().clear();
+      return this;
+    }
+
+    public com.google.protobuf.Descriptors.Descriptor
+        getDescriptorForType() {
+      return io.grpc.alts.internal.AltsContextProto.internal_static_grpc_gcp_AltsContext_descriptor;
+    }
+
+    public io.grpc.alts.internal.AltsContext getDefaultInstanceForType() {
+      return io.grpc.alts.internal.AltsContext.getDefaultInstance();
+    }
+
+    public io.grpc.alts.internal.AltsContext build() {
+      io.grpc.alts.internal.AltsContext result = buildPartial();
+      if (!result.isInitialized()) {
+        throw newUninitializedMessageException(result);
+      }
+      return result;
+    }
+
+    public io.grpc.alts.internal.AltsContext buildPartial() {
+      io.grpc.alts.internal.AltsContext result = new io.grpc.alts.internal.AltsContext(this);
+      int from_bitField0_ = bitField0_;
+      int to_bitField0_ = 0;
+      result.applicationProtocol_ = applicationProtocol_;
+      result.recordProtocol_ = recordProtocol_;
+      result.securityLevel_ = securityLevel_;
+      result.peerServiceAccount_ = peerServiceAccount_;
+      result.localServiceAccount_ = localServiceAccount_;
+      if (peerRpcVersionsBuilder_ == null) {
+        result.peerRpcVersions_ = peerRpcVersions_;
+      } else {
+        result.peerRpcVersions_ = peerRpcVersionsBuilder_.build();
+      }
+      result.peerAttributes_ = internalGetPeerAttributes();
+      result.peerAttributes_.makeImmutable();
+      result.bitField0_ = to_bitField0_;
+      onBuilt();
+      return result;
+    }
+
+    public Builder clone() {
+      return (Builder) super.clone();
+    }
+    public Builder setField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.setField(field, value);
+    }
+    public Builder clearField(
+        com.google.protobuf.Descriptors.FieldDescriptor field) {
+      return (Builder) super.clearField(field);
+    }
+    public Builder clearOneof(
+        com.google.protobuf.Descriptors.OneofDescriptor oneof) {
+      return (Builder) super.clearOneof(oneof);
+    }
+    public Builder setRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        int index, java.lang.Object value) {
+      return (Builder) super.setRepeatedField(field, index, value);
+    }
+    public Builder addRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.addRepeatedField(field, value);
+    }
+    public Builder mergeFrom(com.google.protobuf.Message other) {
+      if (other instanceof io.grpc.alts.internal.AltsContext) {
+        return mergeFrom((io.grpc.alts.internal.AltsContext)other);
+      } else {
+        super.mergeFrom(other);
+        return this;
+      }
+    }
+
+    public Builder mergeFrom(io.grpc.alts.internal.AltsContext other) {
+      if (other == io.grpc.alts.internal.AltsContext.getDefaultInstance()) return this;
+      if (!other.getApplicationProtocol().isEmpty()) {
+        applicationProtocol_ = other.applicationProtocol_;
+        onChanged();
+      }
+      if (!other.getRecordProtocol().isEmpty()) {
+        recordProtocol_ = other.recordProtocol_;
+        onChanged();
+      }
+      if (other.securityLevel_ != 0) {
+        setSecurityLevelValue(other.getSecurityLevelValue());
+      }
+      if (!other.getPeerServiceAccount().isEmpty()) {
+        peerServiceAccount_ = other.peerServiceAccount_;
+        onChanged();
+      }
+      if (!other.getLocalServiceAccount().isEmpty()) {
+        localServiceAccount_ = other.localServiceAccount_;
+        onChanged();
+      }
+      if (other.hasPeerRpcVersions()) {
+        mergePeerRpcVersions(other.getPeerRpcVersions());
+      }
+      internalGetMutablePeerAttributes().mergeFrom(
+          other.internalGetPeerAttributes());
+      this.mergeUnknownFields(other.unknownFields);
+      onChanged();
+      return this;
+    }
+
+    public final boolean isInitialized() {
+      return true;
+    }
+
+    public Builder mergeFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      io.grpc.alts.internal.AltsContext parsedMessage = null;
+      try {
+        parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);
+      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+        parsedMessage = (io.grpc.alts.internal.AltsContext) e.getUnfinishedMessage();
+        throw e.unwrapIOException();
+      } finally {
+        if (parsedMessage != null) {
+          mergeFrom(parsedMessage);
+        }
+      }
+      return this;
+    }
+    private int bitField0_;
+
+    private java.lang.Object applicationProtocol_ = "";
+    /**
+     * <pre>
+     * The application protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string application_protocol = 1;</code>
+     */
+    public java.lang.String getApplicationProtocol() {
+      java.lang.Object ref = applicationProtocol_;
+      if (!(ref instanceof java.lang.String)) {
+        com.google.protobuf.ByteString bs =
+            (com.google.protobuf.ByteString) ref;
+        java.lang.String s = bs.toStringUtf8();
+        applicationProtocol_ = s;
+        return s;
+      } else {
+        return (java.lang.String) ref;
+      }
+    }
+    /**
+     * <pre>
+     * The application protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string application_protocol = 1;</code>
+     */
+    public com.google.protobuf.ByteString
+        getApplicationProtocolBytes() {
+      java.lang.Object ref = applicationProtocol_;
+      if (ref instanceof String) {
+        com.google.protobuf.ByteString b = 
+            com.google.protobuf.ByteString.copyFromUtf8(
+                (java.lang.String) ref);
+        applicationProtocol_ = b;
+        return b;
+      } else {
+        return (com.google.protobuf.ByteString) ref;
+      }
+    }
+    /**
+     * <pre>
+     * The application protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string application_protocol = 1;</code>
+     */
+    public Builder setApplicationProtocol(
+        java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  
+      applicationProtocol_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The application protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string application_protocol = 1;</code>
+     */
+    public Builder clearApplicationProtocol() {
+      
+      applicationProtocol_ = getDefaultInstance().getApplicationProtocol();
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The application protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string application_protocol = 1;</code>
+     */
+    public Builder setApplicationProtocolBytes(
+        com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  checkByteStringIsUtf8(value);
+      
+      applicationProtocol_ = value;
+      onChanged();
+      return this;
+    }
+
+    private java.lang.Object recordProtocol_ = "";
+    /**
+     * <pre>
+     * The record protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string record_protocol = 2;</code>
+     */
+    public java.lang.String getRecordProtocol() {
+      java.lang.Object ref = recordProtocol_;
+      if (!(ref instanceof java.lang.String)) {
+        com.google.protobuf.ByteString bs =
+            (com.google.protobuf.ByteString) ref;
+        java.lang.String s = bs.toStringUtf8();
+        recordProtocol_ = s;
+        return s;
+      } else {
+        return (java.lang.String) ref;
+      }
+    }
+    /**
+     * <pre>
+     * The record protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string record_protocol = 2;</code>
+     */
+    public com.google.protobuf.ByteString
+        getRecordProtocolBytes() {
+      java.lang.Object ref = recordProtocol_;
+      if (ref instanceof String) {
+        com.google.protobuf.ByteString b = 
+            com.google.protobuf.ByteString.copyFromUtf8(
+                (java.lang.String) ref);
+        recordProtocol_ = b;
+        return b;
+      } else {
+        return (com.google.protobuf.ByteString) ref;
+      }
+    }
+    /**
+     * <pre>
+     * The record protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string record_protocol = 2;</code>
+     */
+    public Builder setRecordProtocol(
+        java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  
+      recordProtocol_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The record protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string record_protocol = 2;</code>
+     */
+    public Builder clearRecordProtocol() {
+      
+      recordProtocol_ = getDefaultInstance().getRecordProtocol();
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The record protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string record_protocol = 2;</code>
+     */
+    public Builder setRecordProtocolBytes(
+        com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  checkByteStringIsUtf8(value);
+      
+      recordProtocol_ = value;
+      onChanged();
+      return this;
+    }
+
+    private int securityLevel_ = 0;
+    /**
+     * <pre>
+     * The security level of the created secure channel.
+     * </pre>
+     *
+     * <code>.grpc.gcp.SecurityLevel security_level = 3;</code>
+     */
+    public int getSecurityLevelValue() {
+      return securityLevel_;
+    }
+    /**
+     * <pre>
+     * The security level of the created secure channel.
+     * </pre>
+     *
+     * <code>.grpc.gcp.SecurityLevel security_level = 3;</code>
+     */
+    public Builder setSecurityLevelValue(int value) {
+      securityLevel_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The security level of the created secure channel.
+     * </pre>
+     *
+     * <code>.grpc.gcp.SecurityLevel security_level = 3;</code>
+     */
+    public io.grpc.alts.internal.SecurityLevel getSecurityLevel() {
+      io.grpc.alts.internal.SecurityLevel result = io.grpc.alts.internal.SecurityLevel.valueOf(securityLevel_);
+      return result == null ? io.grpc.alts.internal.SecurityLevel.UNRECOGNIZED : result;
+    }
+    /**
+     * <pre>
+     * The security level of the created secure channel.
+     * </pre>
+     *
+     * <code>.grpc.gcp.SecurityLevel security_level = 3;</code>
+     */
+    public Builder setSecurityLevel(io.grpc.alts.internal.SecurityLevel value) {
+      if (value == null) {
+        throw new NullPointerException();
+      }
+      
+      securityLevel_ = value.getNumber();
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The security level of the created secure channel.
+     * </pre>
+     *
+     * <code>.grpc.gcp.SecurityLevel security_level = 3;</code>
+     */
+    public Builder clearSecurityLevel() {
+      
+      securityLevel_ = 0;
+      onChanged();
+      return this;
+    }
+
+    private java.lang.Object peerServiceAccount_ = "";
+    /**
+     * <pre>
+     * The peer service account.
+     * </pre>
+     *
+     * <code>string peer_service_account = 4;</code>
+     */
+    public java.lang.String getPeerServiceAccount() {
+      java.lang.Object ref = peerServiceAccount_;
+      if (!(ref instanceof java.lang.String)) {
+        com.google.protobuf.ByteString bs =
+            (com.google.protobuf.ByteString) ref;
+        java.lang.String s = bs.toStringUtf8();
+        peerServiceAccount_ = s;
+        return s;
+      } else {
+        return (java.lang.String) ref;
+      }
+    }
+    /**
+     * <pre>
+     * The peer service account.
+     * </pre>
+     *
+     * <code>string peer_service_account = 4;</code>
+     */
+    public com.google.protobuf.ByteString
+        getPeerServiceAccountBytes() {
+      java.lang.Object ref = peerServiceAccount_;
+      if (ref instanceof String) {
+        com.google.protobuf.ByteString b = 
+            com.google.protobuf.ByteString.copyFromUtf8(
+                (java.lang.String) ref);
+        peerServiceAccount_ = b;
+        return b;
+      } else {
+        return (com.google.protobuf.ByteString) ref;
+      }
+    }
+    /**
+     * <pre>
+     * The peer service account.
+     * </pre>
+     *
+     * <code>string peer_service_account = 4;</code>
+     */
+    public Builder setPeerServiceAccount(
+        java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  
+      peerServiceAccount_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The peer service account.
+     * </pre>
+     *
+     * <code>string peer_service_account = 4;</code>
+     */
+    public Builder clearPeerServiceAccount() {
+      
+      peerServiceAccount_ = getDefaultInstance().getPeerServiceAccount();
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The peer service account.
+     * </pre>
+     *
+     * <code>string peer_service_account = 4;</code>
+     */
+    public Builder setPeerServiceAccountBytes(
+        com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  checkByteStringIsUtf8(value);
+      
+      peerServiceAccount_ = value;
+      onChanged();
+      return this;
+    }
+
+    private java.lang.Object localServiceAccount_ = "";
+    /**
+     * <pre>
+     * The local service account.
+     * </pre>
+     *
+     * <code>string local_service_account = 5;</code>
+     */
+    public java.lang.String getLocalServiceAccount() {
+      java.lang.Object ref = localServiceAccount_;
+      if (!(ref instanceof java.lang.String)) {
+        com.google.protobuf.ByteString bs =
+            (com.google.protobuf.ByteString) ref;
+        java.lang.String s = bs.toStringUtf8();
+        localServiceAccount_ = s;
+        return s;
+      } else {
+        return (java.lang.String) ref;
+      }
+    }
+    /**
+     * <pre>
+     * The local service account.
+     * </pre>
+     *
+     * <code>string local_service_account = 5;</code>
+     */
+    public com.google.protobuf.ByteString
+        getLocalServiceAccountBytes() {
+      java.lang.Object ref = localServiceAccount_;
+      if (ref instanceof String) {
+        com.google.protobuf.ByteString b = 
+            com.google.protobuf.ByteString.copyFromUtf8(
+                (java.lang.String) ref);
+        localServiceAccount_ = b;
+        return b;
+      } else {
+        return (com.google.protobuf.ByteString) ref;
+      }
+    }
+    /**
+     * <pre>
+     * The local service account.
+     * </pre>
+     *
+     * <code>string local_service_account = 5;</code>
+     */
+    public Builder setLocalServiceAccount(
+        java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  
+      localServiceAccount_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The local service account.
+     * </pre>
+     *
+     * <code>string local_service_account = 5;</code>
+     */
+    public Builder clearLocalServiceAccount() {
+      
+      localServiceAccount_ = getDefaultInstance().getLocalServiceAccount();
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The local service account.
+     * </pre>
+     *
+     * <code>string local_service_account = 5;</code>
+     */
+    public Builder setLocalServiceAccountBytes(
+        com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  checkByteStringIsUtf8(value);
+      
+      localServiceAccount_ = value;
+      onChanged();
+      return this;
+    }
+
+    private io.grpc.alts.internal.RpcProtocolVersions peerRpcVersions_ = null;
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.RpcProtocolVersions, io.grpc.alts.internal.RpcProtocolVersions.Builder, io.grpc.alts.internal.RpcProtocolVersionsOrBuilder> peerRpcVersionsBuilder_;
+    /**
+     * <pre>
+     * The RPC protocol versions supported by the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
+     */
+    public boolean hasPeerRpcVersions() {
+      return peerRpcVersionsBuilder_ != null || peerRpcVersions_ != null;
+    }
+    /**
+     * <pre>
+     * The RPC protocol versions supported by the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
+     */
+    public io.grpc.alts.internal.RpcProtocolVersions getPeerRpcVersions() {
+      if (peerRpcVersionsBuilder_ == null) {
+        return peerRpcVersions_ == null ? io.grpc.alts.internal.RpcProtocolVersions.getDefaultInstance() : peerRpcVersions_;
+      } else {
+        return peerRpcVersionsBuilder_.getMessage();
+      }
+    }
+    /**
+     * <pre>
+     * The RPC protocol versions supported by the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
+     */
+    public Builder setPeerRpcVersions(io.grpc.alts.internal.RpcProtocolVersions value) {
+      if (peerRpcVersionsBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        peerRpcVersions_ = value;
+        onChanged();
+      } else {
+        peerRpcVersionsBuilder_.setMessage(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * The RPC protocol versions supported by the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
+     */
+    public Builder setPeerRpcVersions(
+        io.grpc.alts.internal.RpcProtocolVersions.Builder builderForValue) {
+      if (peerRpcVersionsBuilder_ == null) {
+        peerRpcVersions_ = builderForValue.build();
+        onChanged();
+      } else {
+        peerRpcVersionsBuilder_.setMessage(builderForValue.build());
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * The RPC protocol versions supported by the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
+     */
+    public Builder mergePeerRpcVersions(io.grpc.alts.internal.RpcProtocolVersions value) {
+      if (peerRpcVersionsBuilder_ == null) {
+        if (peerRpcVersions_ != null) {
+          peerRpcVersions_ =
+            io.grpc.alts.internal.RpcProtocolVersions.newBuilder(peerRpcVersions_).mergeFrom(value).buildPartial();
+        } else {
+          peerRpcVersions_ = value;
+        }
+        onChanged();
+      } else {
+        peerRpcVersionsBuilder_.mergeFrom(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * The RPC protocol versions supported by the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
+     */
+    public Builder clearPeerRpcVersions() {
+      if (peerRpcVersionsBuilder_ == null) {
+        peerRpcVersions_ = null;
+        onChanged();
+      } else {
+        peerRpcVersions_ = null;
+        peerRpcVersionsBuilder_ = null;
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * The RPC protocol versions supported by the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
+     */
+    public io.grpc.alts.internal.RpcProtocolVersions.Builder getPeerRpcVersionsBuilder() {
+      
+      onChanged();
+      return getPeerRpcVersionsFieldBuilder().getBuilder();
+    }
+    /**
+     * <pre>
+     * The RPC protocol versions supported by the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
+     */
+    public io.grpc.alts.internal.RpcProtocolVersionsOrBuilder getPeerRpcVersionsOrBuilder() {
+      if (peerRpcVersionsBuilder_ != null) {
+        return peerRpcVersionsBuilder_.getMessageOrBuilder();
+      } else {
+        return peerRpcVersions_ == null ?
+            io.grpc.alts.internal.RpcProtocolVersions.getDefaultInstance() : peerRpcVersions_;
+      }
+    }
+    /**
+     * <pre>
+     * The RPC protocol versions supported by the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
+     */
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.RpcProtocolVersions, io.grpc.alts.internal.RpcProtocolVersions.Builder, io.grpc.alts.internal.RpcProtocolVersionsOrBuilder> 
+        getPeerRpcVersionsFieldBuilder() {
+      if (peerRpcVersionsBuilder_ == null) {
+        peerRpcVersionsBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
+            io.grpc.alts.internal.RpcProtocolVersions, io.grpc.alts.internal.RpcProtocolVersions.Builder, io.grpc.alts.internal.RpcProtocolVersionsOrBuilder>(
+                getPeerRpcVersions(),
+                getParentForChildren(),
+                isClean());
+        peerRpcVersions_ = null;
+      }
+      return peerRpcVersionsBuilder_;
+    }
+
+    private com.google.protobuf.MapField<
+        java.lang.String, java.lang.String> peerAttributes_;
+    private com.google.protobuf.MapField<java.lang.String, java.lang.String>
+    internalGetPeerAttributes() {
+      if (peerAttributes_ == null) {
+        return com.google.protobuf.MapField.emptyMapField(
+            PeerAttributesDefaultEntryHolder.defaultEntry);
+      }
+      return peerAttributes_;
+    }
+    private com.google.protobuf.MapField<java.lang.String, java.lang.String>
+    internalGetMutablePeerAttributes() {
+      onChanged();;
+      if (peerAttributes_ == null) {
+        peerAttributes_ = com.google.protobuf.MapField.newMapField(
+            PeerAttributesDefaultEntryHolder.defaultEntry);
+      }
+      if (!peerAttributes_.isMutable()) {
+        peerAttributes_ = peerAttributes_.copy();
+      }
+      return peerAttributes_;
+    }
+
+    public int getPeerAttributesCount() {
+      return internalGetPeerAttributes().getMap().size();
+    }
+    /**
+     * <pre>
+     * Additional attributes of the peer.
+     * </pre>
+     *
+     * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
+     */
+
+    public boolean containsPeerAttributes(
+        java.lang.String key) {
+      if (key == null) { throw new java.lang.NullPointerException(); }
+      return internalGetPeerAttributes().getMap().containsKey(key);
+    }
+    /**
+     * Use {@link #getPeerAttributesMap()} instead.
+     */
+    @java.lang.Deprecated
+    public java.util.Map<java.lang.String, java.lang.String> getPeerAttributes() {
+      return getPeerAttributesMap();
+    }
+    /**
+     * <pre>
+     * Additional attributes of the peer.
+     * </pre>
+     *
+     * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
+     */
+
+    public java.util.Map<java.lang.String, java.lang.String> getPeerAttributesMap() {
+      return internalGetPeerAttributes().getMap();
+    }
+    /**
+     * <pre>
+     * Additional attributes of the peer.
+     * </pre>
+     *
+     * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
+     */
+
+    public java.lang.String getPeerAttributesOrDefault(
+        java.lang.String key,
+        java.lang.String defaultValue) {
+      if (key == null) { throw new java.lang.NullPointerException(); }
+      java.util.Map<java.lang.String, java.lang.String> map =
+          internalGetPeerAttributes().getMap();
+      return map.containsKey(key) ? map.get(key) : defaultValue;
+    }
+    /**
+     * <pre>
+     * Additional attributes of the peer.
+     * </pre>
+     *
+     * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
+     */
+
+    public java.lang.String getPeerAttributesOrThrow(
+        java.lang.String key) {
+      if (key == null) { throw new java.lang.NullPointerException(); }
+      java.util.Map<java.lang.String, java.lang.String> map =
+          internalGetPeerAttributes().getMap();
+      if (!map.containsKey(key)) {
+        throw new java.lang.IllegalArgumentException();
+      }
+      return map.get(key);
+    }
+
+    public Builder clearPeerAttributes() {
+      internalGetMutablePeerAttributes().getMutableMap()
+          .clear();
+      return this;
+    }
+    /**
+     * <pre>
+     * Additional attributes of the peer.
+     * </pre>
+     *
+     * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
+     */
+
+    public Builder removePeerAttributes(
+        java.lang.String key) {
+      if (key == null) { throw new java.lang.NullPointerException(); }
+      internalGetMutablePeerAttributes().getMutableMap()
+          .remove(key);
+      return this;
+    }
+    /**
+     * Use alternate mutation accessors instead.
+     */
+    @java.lang.Deprecated
+    public java.util.Map<java.lang.String, java.lang.String>
+    getMutablePeerAttributes() {
+      return internalGetMutablePeerAttributes().getMutableMap();
+    }
+    /**
+     * <pre>
+     * Additional attributes of the peer.
+     * </pre>
+     *
+     * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
+     */
+    public Builder putPeerAttributes(
+        java.lang.String key,
+        java.lang.String value) {
+      if (key == null) { throw new java.lang.NullPointerException(); }
+      if (value == null) { throw new java.lang.NullPointerException(); }
+      internalGetMutablePeerAttributes().getMutableMap()
+          .put(key, value);
+      return this;
+    }
+    /**
+     * <pre>
+     * Additional attributes of the peer.
+     * </pre>
+     *
+     * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
+     */
+
+    public Builder putAllPeerAttributes(
+        java.util.Map<java.lang.String, java.lang.String> values) {
+      internalGetMutablePeerAttributes().getMutableMap()
+          .putAll(values);
+      return this;
+    }
+    public final Builder setUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.setUnknownFieldsProto3(unknownFields);
+    }
+
+    public final Builder mergeUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.mergeUnknownFields(unknownFields);
+    }
+
+
+    // @@protoc_insertion_point(builder_scope:grpc.gcp.AltsContext)
+  }
+
+  // @@protoc_insertion_point(class_scope:grpc.gcp.AltsContext)
+  private static final io.grpc.alts.internal.AltsContext DEFAULT_INSTANCE;
+  static {
+    DEFAULT_INSTANCE = new io.grpc.alts.internal.AltsContext();
+  }
+
+  public static io.grpc.alts.internal.AltsContext getDefaultInstance() {
+    return DEFAULT_INSTANCE;
+  }
+
+  private static final com.google.protobuf.Parser<AltsContext>
+      PARSER = new com.google.protobuf.AbstractParser<AltsContext>() {
+    public AltsContext parsePartialFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return new AltsContext(input, extensionRegistry);
+    }
+  };
+
+  public static com.google.protobuf.Parser<AltsContext> parser() {
+    return PARSER;
+  }
+
+  @java.lang.Override
+  public com.google.protobuf.Parser<AltsContext> getParserForType() {
+    return PARSER;
+  }
+
+  public io.grpc.alts.internal.AltsContext getDefaultInstanceForType() {
+    return DEFAULT_INSTANCE;
+  }
+
+}
+
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/AltsContextOrBuilder.java b/alts/src/generated/main/java/io/grpc/alts/internal/AltsContextOrBuilder.java
new file mode 100644
index 0000000000..ee8cfe13f3
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/AltsContextOrBuilder.java
@@ -0,0 +1,177 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/altscontext.proto
+
+package io.grpc.alts.internal;
+
+public interface AltsContextOrBuilder extends
+    // @@protoc_insertion_point(interface_extends:grpc.gcp.AltsContext)
+    com.google.protobuf.MessageOrBuilder {
+
+  /**
+   * <pre>
+   * The application protocol negotiated for this connection.
+   * </pre>
+   *
+   * <code>string application_protocol = 1;</code>
+   */
+  java.lang.String getApplicationProtocol();
+  /**
+   * <pre>
+   * The application protocol negotiated for this connection.
+   * </pre>
+   *
+   * <code>string application_protocol = 1;</code>
+   */
+  com.google.protobuf.ByteString
+      getApplicationProtocolBytes();
+
+  /**
+   * <pre>
+   * The record protocol negotiated for this connection.
+   * </pre>
+   *
+   * <code>string record_protocol = 2;</code>
+   */
+  java.lang.String getRecordProtocol();
+  /**
+   * <pre>
+   * The record protocol negotiated for this connection.
+   * </pre>
+   *
+   * <code>string record_protocol = 2;</code>
+   */
+  com.google.protobuf.ByteString
+      getRecordProtocolBytes();
+
+  /**
+   * <pre>
+   * The security level of the created secure channel.
+   * </pre>
+   *
+   * <code>.grpc.gcp.SecurityLevel security_level = 3;</code>
+   */
+  int getSecurityLevelValue();
+  /**
+   * <pre>
+   * The security level of the created secure channel.
+   * </pre>
+   *
+   * <code>.grpc.gcp.SecurityLevel security_level = 3;</code>
+   */
+  io.grpc.alts.internal.SecurityLevel getSecurityLevel();
+
+  /**
+   * <pre>
+   * The peer service account.
+   * </pre>
+   *
+   * <code>string peer_service_account = 4;</code>
+   */
+  java.lang.String getPeerServiceAccount();
+  /**
+   * <pre>
+   * The peer service account.
+   * </pre>
+   *
+   * <code>string peer_service_account = 4;</code>
+   */
+  com.google.protobuf.ByteString
+      getPeerServiceAccountBytes();
+
+  /**
+   * <pre>
+   * The local service account.
+   * </pre>
+   *
+   * <code>string local_service_account = 5;</code>
+   */
+  java.lang.String getLocalServiceAccount();
+  /**
+   * <pre>
+   * The local service account.
+   * </pre>
+   *
+   * <code>string local_service_account = 5;</code>
+   */
+  com.google.protobuf.ByteString
+      getLocalServiceAccountBytes();
+
+  /**
+   * <pre>
+   * The RPC protocol versions supported by the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
+   */
+  boolean hasPeerRpcVersions();
+  /**
+   * <pre>
+   * The RPC protocol versions supported by the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
+   */
+  io.grpc.alts.internal.RpcProtocolVersions getPeerRpcVersions();
+  /**
+   * <pre>
+   * The RPC protocol versions supported by the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
+   */
+  io.grpc.alts.internal.RpcProtocolVersionsOrBuilder getPeerRpcVersionsOrBuilder();
+
+  /**
+   * <pre>
+   * Additional attributes of the peer.
+   * </pre>
+   *
+   * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
+   */
+  int getPeerAttributesCount();
+  /**
+   * <pre>
+   * Additional attributes of the peer.
+   * </pre>
+   *
+   * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
+   */
+  boolean containsPeerAttributes(
+      java.lang.String key);
+  /**
+   * Use {@link #getPeerAttributesMap()} instead.
+   */
+  @java.lang.Deprecated
+  java.util.Map<java.lang.String, java.lang.String>
+  getPeerAttributes();
+  /**
+   * <pre>
+   * Additional attributes of the peer.
+   * </pre>
+   *
+   * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
+   */
+  java.util.Map<java.lang.String, java.lang.String>
+  getPeerAttributesMap();
+  /**
+   * <pre>
+   * Additional attributes of the peer.
+   * </pre>
+   *
+   * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
+   */
+
+  java.lang.String getPeerAttributesOrDefault(
+      java.lang.String key,
+      java.lang.String defaultValue);
+  /**
+   * <pre>
+   * Additional attributes of the peer.
+   * </pre>
+   *
+   * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
+   */
+
+  java.lang.String getPeerAttributesOrThrow(
+      java.lang.String key);
+}
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/AltsContextProto.java b/alts/src/generated/main/java/io/grpc/alts/internal/AltsContextProto.java
new file mode 100644
index 0000000000..da27b40537
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/AltsContextProto.java
@@ -0,0 +1,80 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/altscontext.proto
+
+package io.grpc.alts.internal;
+
+public final class AltsContextProto {
+  private AltsContextProto() {}
+  public static void registerAllExtensions(
+      com.google.protobuf.ExtensionRegistryLite registry) {
+  }
+
+  public static void registerAllExtensions(
+      com.google.protobuf.ExtensionRegistry registry) {
+    registerAllExtensions(
+        (com.google.protobuf.ExtensionRegistryLite) registry);
+  }
+  static final com.google.protobuf.Descriptors.Descriptor
+    internal_static_grpc_gcp_AltsContext_descriptor;
+  static final 
+    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internal_static_grpc_gcp_AltsContext_fieldAccessorTable;
+  static final com.google.protobuf.Descriptors.Descriptor
+    internal_static_grpc_gcp_AltsContext_PeerAttributesEntry_descriptor;
+  static final 
+    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internal_static_grpc_gcp_AltsContext_PeerAttributesEntry_fieldAccessorTable;
+
+  public static com.google.protobuf.Descriptors.FileDescriptor
+      getDescriptor() {
+    return descriptor;
+  }
+  private static  com.google.protobuf.Descriptors.FileDescriptor
+      descriptor;
+  static {
+    java.lang.String[] descriptorData = {
+      "\n\032grpc/gcp/altscontext.proto\022\010grpc.gcp\032(" +
+      "grpc/gcp/transport_security_common.proto" +
+      "\"\347\002\n\013AltsContext\022\034\n\024application_protocol" +
+      "\030\001 \001(\t\022\027\n\017record_protocol\030\002 \001(\t\022/\n\016secur" +
+      "ity_level\030\003 \001(\0162\027.grpc.gcp.SecurityLevel" +
+      "\022\034\n\024peer_service_account\030\004 \001(\t\022\035\n\025local_" +
+      "service_account\030\005 \001(\t\0228\n\021peer_rpc_versio" +
+      "ns\030\006 \001(\0132\035.grpc.gcp.RpcProtocolVersions\022" +
+      "B\n\017peer_attributes\030\007 \003(\0132).grpc.gcp.Alts" +
+      "Context.PeerAttributesEntry\0325\n\023PeerAttri" +
+      "butesEntry\022\013\n\003key\030\001 \001(\t\022\r\n\005value\030\002 \001(\t:\002" +
+      "8\001Bl\n\025io.grpc.alts.internalB\020AltsContext" +
+      "ProtoP\001Z?google.golang.org/grpc/credenti" +
+      "als/alts/internal/proto/grpc_gcpb\006proto3"
+    };
+    com.google.protobuf.Descriptors.FileDescriptor.InternalDescriptorAssigner assigner =
+        new com.google.protobuf.Descriptors.FileDescriptor.    InternalDescriptorAssigner() {
+          public com.google.protobuf.ExtensionRegistry assignDescriptors(
+              com.google.protobuf.Descriptors.FileDescriptor root) {
+            descriptor = root;
+            return null;
+          }
+        };
+    com.google.protobuf.Descriptors.FileDescriptor
+      .internalBuildGeneratedFileFrom(descriptorData,
+        new com.google.protobuf.Descriptors.FileDescriptor[] {
+          io.grpc.alts.internal.TransportSecurityCommonProto.getDescriptor(),
+        }, assigner);
+    internal_static_grpc_gcp_AltsContext_descriptor =
+      getDescriptor().getMessageTypes().get(0);
+    internal_static_grpc_gcp_AltsContext_fieldAccessorTable = new
+      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
+        internal_static_grpc_gcp_AltsContext_descriptor,
+        new java.lang.String[] { "ApplicationProtocol", "RecordProtocol", "SecurityLevel", "PeerServiceAccount", "LocalServiceAccount", "PeerRpcVersions", "PeerAttributes", });
+    internal_static_grpc_gcp_AltsContext_PeerAttributesEntry_descriptor =
+      internal_static_grpc_gcp_AltsContext_descriptor.getNestedTypes().get(0);
+    internal_static_grpc_gcp_AltsContext_PeerAttributesEntry_fieldAccessorTable = new
+      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
+        internal_static_grpc_gcp_AltsContext_PeerAttributesEntry_descriptor,
+        new java.lang.String[] { "Key", "Value", });
+    io.grpc.alts.internal.TransportSecurityCommonProto.getDescriptor();
+  }
+
+  // @@protoc_insertion_point(outer_class_scope)
+}
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/Altscontext.java b/alts/src/generated/main/java/io/grpc/alts/internal/Altscontext.java
deleted file mode 100644
index 9e40b65b6c..0000000000
--- a/alts/src/generated/main/java/io/grpc/alts/internal/Altscontext.java
+++ /dev/null
@@ -1,1915 +0,0 @@
-// Generated by the protocol buffer compiler.  DO NOT EDIT!
-// source: grpc/gcp/altscontext.proto
-
-package io.grpc.alts.internal;
-
-public final class Altscontext {
-  private Altscontext() {}
-  public static void registerAllExtensions(
-      com.google.protobuf.ExtensionRegistryLite registry) {
-  }
-
-  public static void registerAllExtensions(
-      com.google.protobuf.ExtensionRegistry registry) {
-    registerAllExtensions(
-        (com.google.protobuf.ExtensionRegistryLite) registry);
-  }
-  public interface AltsContextOrBuilder extends
-      // @@protoc_insertion_point(interface_extends:grpc.gcp.AltsContext)
-      com.google.protobuf.MessageOrBuilder {
-
-    /**
-     * <pre>
-     * The application protocol negotiated for this connection.
-     * </pre>
-     *
-     * <code>string application_protocol = 1;</code>
-     */
-    java.lang.String getApplicationProtocol();
-    /**
-     * <pre>
-     * The application protocol negotiated for this connection.
-     * </pre>
-     *
-     * <code>string application_protocol = 1;</code>
-     */
-    com.google.protobuf.ByteString
-        getApplicationProtocolBytes();
-
-    /**
-     * <pre>
-     * The record protocol negotiated for this connection.
-     * </pre>
-     *
-     * <code>string record_protocol = 2;</code>
-     */
-    java.lang.String getRecordProtocol();
-    /**
-     * <pre>
-     * The record protocol negotiated for this connection.
-     * </pre>
-     *
-     * <code>string record_protocol = 2;</code>
-     */
-    com.google.protobuf.ByteString
-        getRecordProtocolBytes();
-
-    /**
-     * <pre>
-     * The security level of the created secure channel.
-     * </pre>
-     *
-     * <code>.grpc.gcp.SecurityLevel security_level = 3;</code>
-     */
-    int getSecurityLevelValue();
-    /**
-     * <pre>
-     * The security level of the created secure channel.
-     * </pre>
-     *
-     * <code>.grpc.gcp.SecurityLevel security_level = 3;</code>
-     */
-    io.grpc.alts.internal.TransportSecurityCommon.SecurityLevel getSecurityLevel();
-
-    /**
-     * <pre>
-     * The peer service account.
-     * </pre>
-     *
-     * <code>string peer_service_account = 4;</code>
-     */
-    java.lang.String getPeerServiceAccount();
-    /**
-     * <pre>
-     * The peer service account.
-     * </pre>
-     *
-     * <code>string peer_service_account = 4;</code>
-     */
-    com.google.protobuf.ByteString
-        getPeerServiceAccountBytes();
-
-    /**
-     * <pre>
-     * The local service account.
-     * </pre>
-     *
-     * <code>string local_service_account = 5;</code>
-     */
-    java.lang.String getLocalServiceAccount();
-    /**
-     * <pre>
-     * The local service account.
-     * </pre>
-     *
-     * <code>string local_service_account = 5;</code>
-     */
-    com.google.protobuf.ByteString
-        getLocalServiceAccountBytes();
-
-    /**
-     * <pre>
-     * The RPC protocol versions supported by the peer.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
-     */
-    boolean hasPeerRpcVersions();
-    /**
-     * <pre>
-     * The RPC protocol versions supported by the peer.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
-     */
-    io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions getPeerRpcVersions();
-    /**
-     * <pre>
-     * The RPC protocol versions supported by the peer.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
-     */
-    io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersionsOrBuilder getPeerRpcVersionsOrBuilder();
-
-    /**
-     * <pre>
-     * Additional attributes of the peer.
-     * </pre>
-     *
-     * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
-     */
-    int getPeerAttributesCount();
-    /**
-     * <pre>
-     * Additional attributes of the peer.
-     * </pre>
-     *
-     * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
-     */
-    boolean containsPeerAttributes(
-        java.lang.String key);
-    /**
-     * Use {@link #getPeerAttributesMap()} instead.
-     */
-    @java.lang.Deprecated
-    java.util.Map<java.lang.String, java.lang.String>
-    getPeerAttributes();
-    /**
-     * <pre>
-     * Additional attributes of the peer.
-     * </pre>
-     *
-     * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
-     */
-    java.util.Map<java.lang.String, java.lang.String>
-    getPeerAttributesMap();
-    /**
-     * <pre>
-     * Additional attributes of the peer.
-     * </pre>
-     *
-     * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
-     */
-
-    java.lang.String getPeerAttributesOrDefault(
-        java.lang.String key,
-        java.lang.String defaultValue);
-    /**
-     * <pre>
-     * Additional attributes of the peer.
-     * </pre>
-     *
-     * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
-     */
-
-    java.lang.String getPeerAttributesOrThrow(
-        java.lang.String key);
-  }
-  /**
-   * Protobuf type {@code grpc.gcp.AltsContext}
-   */
-  public  static final class AltsContext extends
-      com.google.protobuf.GeneratedMessageV3 implements
-      // @@protoc_insertion_point(message_implements:grpc.gcp.AltsContext)
-      AltsContextOrBuilder {
-  private static final long serialVersionUID = 0L;
-    // Use AltsContext.newBuilder() to construct.
-    private AltsContext(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
-      super(builder);
-    }
-    private AltsContext() {
-      applicationProtocol_ = "";
-      recordProtocol_ = "";
-      securityLevel_ = 0;
-      peerServiceAccount_ = "";
-      localServiceAccount_ = "";
-    }
-
-    @java.lang.Override
-    public final com.google.protobuf.UnknownFieldSet
-    getUnknownFields() {
-      return this.unknownFields;
-    }
-    private AltsContext(
-        com.google.protobuf.CodedInputStream input,
-        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-        throws com.google.protobuf.InvalidProtocolBufferException {
-      this();
-      if (extensionRegistry == null) {
-        throw new java.lang.NullPointerException();
-      }
-      int mutable_bitField0_ = 0;
-      com.google.protobuf.UnknownFieldSet.Builder unknownFields =
-          com.google.protobuf.UnknownFieldSet.newBuilder();
-      try {
-        boolean done = false;
-        while (!done) {
-          int tag = input.readTag();
-          switch (tag) {
-            case 0:
-              done = true;
-              break;
-            default: {
-              if (!parseUnknownFieldProto3(
-                  input, unknownFields, extensionRegistry, tag)) {
-                done = true;
-              }
-              break;
-            }
-            case 10: {
-              java.lang.String s = input.readStringRequireUtf8();
-
-              applicationProtocol_ = s;
-              break;
-            }
-            case 18: {
-              java.lang.String s = input.readStringRequireUtf8();
-
-              recordProtocol_ = s;
-              break;
-            }
-            case 24: {
-              int rawValue = input.readEnum();
-
-              securityLevel_ = rawValue;
-              break;
-            }
-            case 34: {
-              java.lang.String s = input.readStringRequireUtf8();
-
-              peerServiceAccount_ = s;
-              break;
-            }
-            case 42: {
-              java.lang.String s = input.readStringRequireUtf8();
-
-              localServiceAccount_ = s;
-              break;
-            }
-            case 50: {
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Builder subBuilder = null;
-              if (peerRpcVersions_ != null) {
-                subBuilder = peerRpcVersions_.toBuilder();
-              }
-              peerRpcVersions_ = input.readMessage(io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.parser(), extensionRegistry);
-              if (subBuilder != null) {
-                subBuilder.mergeFrom(peerRpcVersions_);
-                peerRpcVersions_ = subBuilder.buildPartial();
-              }
-
-              break;
-            }
-            case 58: {
-              if (!((mutable_bitField0_ & 0x00000040) == 0x00000040)) {
-                peerAttributes_ = com.google.protobuf.MapField.newMapField(
-                    PeerAttributesDefaultEntryHolder.defaultEntry);
-                mutable_bitField0_ |= 0x00000040;
-              }
-              com.google.protobuf.MapEntry<java.lang.String, java.lang.String>
-              peerAttributes__ = input.readMessage(
-                  PeerAttributesDefaultEntryHolder.defaultEntry.getParserForType(), extensionRegistry);
-              peerAttributes_.getMutableMap().put(
-                  peerAttributes__.getKey(), peerAttributes__.getValue());
-              break;
-            }
-          }
-        }
-      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
-        throw e.setUnfinishedMessage(this);
-      } catch (java.io.IOException e) {
-        throw new com.google.protobuf.InvalidProtocolBufferException(
-            e).setUnfinishedMessage(this);
-      } finally {
-        this.unknownFields = unknownFields.build();
-        makeExtensionsImmutable();
-      }
-    }
-    public static final com.google.protobuf.Descriptors.Descriptor
-        getDescriptor() {
-      return io.grpc.alts.internal.Altscontext.internal_static_grpc_gcp_AltsContext_descriptor;
-    }
-
-    @SuppressWarnings({"rawtypes"})
-    protected com.google.protobuf.MapField internalGetMapField(
-        int number) {
-      switch (number) {
-        case 7:
-          return internalGetPeerAttributes();
-        default:
-          throw new RuntimeException(
-              "Invalid map field number: " + number);
-      }
-    }
-    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
-        internalGetFieldAccessorTable() {
-      return io.grpc.alts.internal.Altscontext.internal_static_grpc_gcp_AltsContext_fieldAccessorTable
-          .ensureFieldAccessorsInitialized(
-              io.grpc.alts.internal.Altscontext.AltsContext.class, io.grpc.alts.internal.Altscontext.AltsContext.Builder.class);
-    }
-
-    private int bitField0_;
-    public static final int APPLICATION_PROTOCOL_FIELD_NUMBER = 1;
-    private volatile java.lang.Object applicationProtocol_;
-    /**
-     * <pre>
-     * The application protocol negotiated for this connection.
-     * </pre>
-     *
-     * <code>string application_protocol = 1;</code>
-     */
-    public java.lang.String getApplicationProtocol() {
-      java.lang.Object ref = applicationProtocol_;
-      if (ref instanceof java.lang.String) {
-        return (java.lang.String) ref;
-      } else {
-        com.google.protobuf.ByteString bs = 
-            (com.google.protobuf.ByteString) ref;
-        java.lang.String s = bs.toStringUtf8();
-        applicationProtocol_ = s;
-        return s;
-      }
-    }
-    /**
-     * <pre>
-     * The application protocol negotiated for this connection.
-     * </pre>
-     *
-     * <code>string application_protocol = 1;</code>
-     */
-    public com.google.protobuf.ByteString
-        getApplicationProtocolBytes() {
-      java.lang.Object ref = applicationProtocol_;
-      if (ref instanceof java.lang.String) {
-        com.google.protobuf.ByteString b = 
-            com.google.protobuf.ByteString.copyFromUtf8(
-                (java.lang.String) ref);
-        applicationProtocol_ = b;
-        return b;
-      } else {
-        return (com.google.protobuf.ByteString) ref;
-      }
-    }
-
-    public static final int RECORD_PROTOCOL_FIELD_NUMBER = 2;
-    private volatile java.lang.Object recordProtocol_;
-    /**
-     * <pre>
-     * The record protocol negotiated for this connection.
-     * </pre>
-     *
-     * <code>string record_protocol = 2;</code>
-     */
-    public java.lang.String getRecordProtocol() {
-      java.lang.Object ref = recordProtocol_;
-      if (ref instanceof java.lang.String) {
-        return (java.lang.String) ref;
-      } else {
-        com.google.protobuf.ByteString bs = 
-            (com.google.protobuf.ByteString) ref;
-        java.lang.String s = bs.toStringUtf8();
-        recordProtocol_ = s;
-        return s;
-      }
-    }
-    /**
-     * <pre>
-     * The record protocol negotiated for this connection.
-     * </pre>
-     *
-     * <code>string record_protocol = 2;</code>
-     */
-    public com.google.protobuf.ByteString
-        getRecordProtocolBytes() {
-      java.lang.Object ref = recordProtocol_;
-      if (ref instanceof java.lang.String) {
-        com.google.protobuf.ByteString b = 
-            com.google.protobuf.ByteString.copyFromUtf8(
-                (java.lang.String) ref);
-        recordProtocol_ = b;
-        return b;
-      } else {
-        return (com.google.protobuf.ByteString) ref;
-      }
-    }
-
-    public static final int SECURITY_LEVEL_FIELD_NUMBER = 3;
-    private int securityLevel_;
-    /**
-     * <pre>
-     * The security level of the created secure channel.
-     * </pre>
-     *
-     * <code>.grpc.gcp.SecurityLevel security_level = 3;</code>
-     */
-    public int getSecurityLevelValue() {
-      return securityLevel_;
-    }
-    /**
-     * <pre>
-     * The security level of the created secure channel.
-     * </pre>
-     *
-     * <code>.grpc.gcp.SecurityLevel security_level = 3;</code>
-     */
-    public io.grpc.alts.internal.TransportSecurityCommon.SecurityLevel getSecurityLevel() {
-      io.grpc.alts.internal.TransportSecurityCommon.SecurityLevel result = io.grpc.alts.internal.TransportSecurityCommon.SecurityLevel.valueOf(securityLevel_);
-      return result == null ? io.grpc.alts.internal.TransportSecurityCommon.SecurityLevel.UNRECOGNIZED : result;
-    }
-
-    public static final int PEER_SERVICE_ACCOUNT_FIELD_NUMBER = 4;
-    private volatile java.lang.Object peerServiceAccount_;
-    /**
-     * <pre>
-     * The peer service account.
-     * </pre>
-     *
-     * <code>string peer_service_account = 4;</code>
-     */
-    public java.lang.String getPeerServiceAccount() {
-      java.lang.Object ref = peerServiceAccount_;
-      if (ref instanceof java.lang.String) {
-        return (java.lang.String) ref;
-      } else {
-        com.google.protobuf.ByteString bs = 
-            (com.google.protobuf.ByteString) ref;
-        java.lang.String s = bs.toStringUtf8();
-        peerServiceAccount_ = s;
-        return s;
-      }
-    }
-    /**
-     * <pre>
-     * The peer service account.
-     * </pre>
-     *
-     * <code>string peer_service_account = 4;</code>
-     */
-    public com.google.protobuf.ByteString
-        getPeerServiceAccountBytes() {
-      java.lang.Object ref = peerServiceAccount_;
-      if (ref instanceof java.lang.String) {
-        com.google.protobuf.ByteString b = 
-            com.google.protobuf.ByteString.copyFromUtf8(
-                (java.lang.String) ref);
-        peerServiceAccount_ = b;
-        return b;
-      } else {
-        return (com.google.protobuf.ByteString) ref;
-      }
-    }
-
-    public static final int LOCAL_SERVICE_ACCOUNT_FIELD_NUMBER = 5;
-    private volatile java.lang.Object localServiceAccount_;
-    /**
-     * <pre>
-     * The local service account.
-     * </pre>
-     *
-     * <code>string local_service_account = 5;</code>
-     */
-    public java.lang.String getLocalServiceAccount() {
-      java.lang.Object ref = localServiceAccount_;
-      if (ref instanceof java.lang.String) {
-        return (java.lang.String) ref;
-      } else {
-        com.google.protobuf.ByteString bs = 
-            (com.google.protobuf.ByteString) ref;
-        java.lang.String s = bs.toStringUtf8();
-        localServiceAccount_ = s;
-        return s;
-      }
-    }
-    /**
-     * <pre>
-     * The local service account.
-     * </pre>
-     *
-     * <code>string local_service_account = 5;</code>
-     */
-    public com.google.protobuf.ByteString
-        getLocalServiceAccountBytes() {
-      java.lang.Object ref = localServiceAccount_;
-      if (ref instanceof java.lang.String) {
-        com.google.protobuf.ByteString b = 
-            com.google.protobuf.ByteString.copyFromUtf8(
-                (java.lang.String) ref);
-        localServiceAccount_ = b;
-        return b;
-      } else {
-        return (com.google.protobuf.ByteString) ref;
-      }
-    }
-
-    public static final int PEER_RPC_VERSIONS_FIELD_NUMBER = 6;
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-          com.google.protobuf.ByteString bs =
-              (com.google.protobuf.ByteString) ref;
-          java.lang.String s = bs.toStringUtf8();
-          recordProtocol_ = s;
-          return s;
-        } else {
-          return (java.lang.String) ref;
-        }
-      }
-      /**
-       * <pre>
-       * The record protocol negotiated for this connection.
-       * </pre>
-       *
-       * <code>string record_protocol = 2;</code>
-       */
-      public com.google.protobuf.ByteString
-          getRecordProtocolBytes() {
-        java.lang.Object ref = recordProtocol_;
-        if (ref instanceof String) {
-          com.google.protobuf.ByteString b = 
-              com.google.protobuf.ByteString.copyFromUtf8(
-                  (java.lang.String) ref);
-          recordProtocol_ = b;
-          return b;
-        } else {
-          return (com.google.protobuf.ByteString) ref;
-        }
-      }
-      /**
-       * <pre>
-       * The record protocol negotiated for this connection.
-       * </pre>
-       *
-       * <code>string record_protocol = 2;</code>
-       */
-      public Builder setRecordProtocol(
-          java.lang.String value) {
-        if (value == null) {
-    throw new NullPointerException();
-  }
-  
-        recordProtocol_ = value;
-        onChanged();
-        return this;
-      }
-      /**
-       * <pre>
-       * The record protocol negotiated for this connection.
-       * </pre>
-       *
-       * <code>string record_protocol = 2;</code>
-       */
-      public Builder clearRecordProtocol() {
-        
-        recordProtocol_ = getDefaultInstance().getRecordProtocol();
-        onChanged();
-        return this;
-      }
-      /**
-       * <pre>
-       * The record protocol negotiated for this connection.
-       * </pre>
-       *
-       * <code>string record_protocol = 2;</code>
-       */
-      public Builder setRecordProtocolBytes(
-          com.google.protobuf.ByteString value) {
-        if (value == null) {
-    throw new NullPointerException();
-  }
-  checkByteStringIsUtf8(value);
-        
-        recordProtocol_ = value;
-        onChanged();
-        return this;
-      }
-
-      private int securityLevel_ = 0;
-      /**
-       * <pre>
-       * The security level of the created secure channel.
-       * </pre>
-       *
-       * <code>.grpc.gcp.SecurityLevel security_level = 3;</code>
-       */
-      public int getSecurityLevelValue() {
-        return securityLevel_;
-      }
-      /**
-       * <pre>
-       * The security level of the created secure channel.
-       * </pre>
-       *
-       * <code>.grpc.gcp.SecurityLevel security_level = 3;</code>
-       */
-      public Builder setSecurityLevelValue(int value) {
-        securityLevel_ = value;
-        onChanged();
-        return this;
-      }
-      /**
-       * <pre>
-       * The security level of the created secure channel.
-       * </pre>
-       *
-       * <code>.grpc.gcp.SecurityLevel security_level = 3;</code>
-       */
-      public io.grpc.alts.internal.TransportSecurityCommon.SecurityLevel getSecurityLevel() {
-        io.grpc.alts.internal.TransportSecurityCommon.SecurityLevel result = io.grpc.alts.internal.TransportSecurityCommon.SecurityLevel.valueOf(securityLevel_);
-        return result == null ? io.grpc.alts.internal.TransportSecurityCommon.SecurityLevel.UNRECOGNIZED : result;
-      }
-      /**
-       * <pre>
-       * The security level of the created secure channel.
-       * </pre>
-       *
-       * <code>.grpc.gcp.SecurityLevel security_level = 3;</code>
-       */
-      public Builder setSecurityLevel(io.grpc.alts.internal.TransportSecurityCommon.SecurityLevel value) {
-        if (value == null) {
-          throw new NullPointerException();
-        }
-        
-        securityLevel_ = value.getNumber();
-        onChanged();
-        return this;
-      }
-      /**
-       * <pre>
-       * The security level of the created secure channel.
-       * </pre>
-       *
-       * <code>.grpc.gcp.SecurityLevel security_level = 3;</code>
-       */
-      public Builder clearSecurityLevel() {
-        
-        securityLevel_ = 0;
-        onChanged();
-        return this;
-      }
-
-      private java.lang.Object peerServiceAccount_ = "";
-      /**
-       * <pre>
-       * The peer service account.
-       * </pre>
-       *
-       * <code>string peer_service_account = 4;</code>
-       */
-      public java.lang.String getPeerServiceAccount() {
-        java.lang.Object ref = peerServiceAccount_;
-        if (!(ref instanceof java.lang.String)) {
-          com.google.protobuf.ByteString bs =
-              (com.google.protobuf.ByteString) ref;
-          java.lang.String s = bs.toStringUtf8();
-          peerServiceAccount_ = s;
-          return s;
-        } else {
-          return (java.lang.String) ref;
-        }
-      }
-      /**
-       * <pre>
-       * The peer service account.
-       * </pre>
-       *
-       * <code>string peer_service_account = 4;</code>
-       */
-      public com.google.protobuf.ByteString
-          getPeerServiceAccountBytes() {
-        java.lang.Object ref = peerServiceAccount_;
-        if (ref instanceof String) {
-          com.google.protobuf.ByteString b = 
-              com.google.protobuf.ByteString.copyFromUtf8(
-                  (java.lang.String) ref);
-          peerServiceAccount_ = b;
-          return b;
-        } else {
-          return (com.google.protobuf.ByteString) ref;
-        }
-      }
-      /**
-       * <pre>
-       * The peer service account.
-       * </pre>
-       *
-       * <code>string peer_service_account = 4;</code>
-       */
-      public Builder setPeerServiceAccount(
-          java.lang.String value) {
-        if (value == null) {
-    throw new NullPointerException();
-  }
-  
-        peerServiceAccount_ = value;
-        onChanged();
-        return this;
-      }
-      /**
-       * <pre>
-       * The peer service account.
-       * </pre>
-       *
-       * <code>string peer_service_account = 4;</code>
-       */
-      public Builder clearPeerServiceAccount() {
-        
-        peerServiceAccount_ = getDefaultInstance().getPeerServiceAccount();
-        onChanged();
-        return this;
-      }
-      /**
-       * <pre>
-       * The peer service account.
-       * </pre>
-       *
-       * <code>string peer_service_account = 4;</code>
-       */
-      public Builder setPeerServiceAccountBytes(
-          com.google.protobuf.ByteString value) {
-        if (value == null) {
-    throw new NullPointerException();
-  }
-  checkByteStringIsUtf8(value);
-        
-        peerServiceAccount_ = value;
-        onChanged();
-        return this;
-      }
-
-      private java.lang.Object localServiceAccount_ = "";
-      /**
-       * <pre>
-       * The local service account.
-       * </pre>
-       *
-       * <code>string local_service_account = 5;</code>
-       */
-      public java.lang.String getLocalServiceAccount() {
-        java.lang.Object ref = localServiceAccount_;
-        if (!(ref instanceof java.lang.String)) {
-          com.google.protobuf.ByteString bs =
-              (com.google.protobuf.ByteString) ref;
-          java.lang.String s = bs.toStringUtf8();
-          localServiceAccount_ = s;
-          return s;
-        } else {
-          return (java.lang.String) ref;
-        }
-      }
-      /**
-       * <pre>
-       * The local service account.
-       * </pre>
-       *
-       * <code>string local_service_account = 5;</code>
-       */
-      public com.google.protobuf.ByteString
-          getLocalServiceAccountBytes() {
-        java.lang.Object ref = localServiceAccount_;
-        if (ref instanceof String) {
-          com.google.protobuf.ByteString b = 
-              com.google.protobuf.ByteString.copyFromUtf8(
-                  (java.lang.String) ref);
-          localServiceAccount_ = b;
-          return b;
-        } else {
-          return (com.google.protobuf.ByteString) ref;
-        }
-      }
-      /**
-       * <pre>
-       * The local service account.
-       * </pre>
-       *
-       * <code>string local_service_account = 5;</code>
-       */
-      public Builder setLocalServiceAccount(
-          java.lang.String value) {
-        if (value == null) {
-    throw new NullPointerException();
-  }
-  
-        localServiceAccount_ = value;
-        onChanged();
-        return this;
-      }
-      /**
-       * <pre>
-       * The local service account.
-       * </pre>
-       *
-       * <code>string local_service_account = 5;</code>
-       */
-      public Builder clearLocalServiceAccount() {
-        
-        localServiceAccount_ = getDefaultInstance().getLocalServiceAccount();
-        onChanged();
-        return this;
-      }
-      /**
-       * <pre>
-       * The local service account.
-       * </pre>
-       *
-       * <code>string local_service_account = 5;</code>
-       */
-      public Builder setLocalServiceAccountBytes(
-          com.google.protobuf.ByteString value) {
-        if (value == null) {
-    throw new NullPointerException();
-  }
-  checkByteStringIsUtf8(value);
-        
-        localServiceAccount_ = value;
-        onChanged();
-        return this;
-      }
-
-      private io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions peerRpcVersions_ = null;
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Builder, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersionsOrBuilder> peerRpcVersionsBuilder_;
-      /**
-       * <pre>
-       * The RPC protocol versions supported by the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
-       */
-      public boolean hasPeerRpcVersions() {
-        return peerRpcVersionsBuilder_ != null || peerRpcVersions_ != null;
-      }
-      /**
-       * <pre>
-       * The RPC protocol versions supported by the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
-       */
-      public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions getPeerRpcVersions() {
-        if (peerRpcVersionsBuilder_ == null) {
-          return peerRpcVersions_ == null ? io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.getDefaultInstance() : peerRpcVersions_;
-        } else {
-          return peerRpcVersionsBuilder_.getMessage();
-        }
-      }
-      /**
-       * <pre>
-       * The RPC protocol versions supported by the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
-       */
-      public Builder setPeerRpcVersions(io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions value) {
-        if (peerRpcVersionsBuilder_ == null) {
-          if (value == null) {
-            throw new NullPointerException();
-          }
-          peerRpcVersions_ = value;
-          onChanged();
-        } else {
-          peerRpcVersionsBuilder_.setMessage(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * The RPC protocol versions supported by the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
-       */
-      public Builder setPeerRpcVersions(
-          io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Builder builderForValue) {
-        if (peerRpcVersionsBuilder_ == null) {
-          peerRpcVersions_ = builderForValue.build();
-          onChanged();
-        } else {
-          peerRpcVersionsBuilder_.setMessage(builderForValue.build());
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * The RPC protocol versions supported by the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
-       */
-      public Builder mergePeerRpcVersions(io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions value) {
-        if (peerRpcVersionsBuilder_ == null) {
-          if (peerRpcVersions_ != null) {
-            peerRpcVersions_ =
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.newBuilder(peerRpcVersions_).mergeFrom(value).buildPartial();
-          } else {
-            peerRpcVersions_ = value;
-          }
-          onChanged();
-        } else {
-          peerRpcVersionsBuilder_.mergeFrom(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * The RPC protocol versions supported by the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
-       */
-      public Builder clearPeerRpcVersions() {
-        if (peerRpcVersionsBuilder_ == null) {
-          peerRpcVersions_ = null;
-          onChanged();
-        } else {
-          peerRpcVersions_ = null;
-          peerRpcVersionsBuilder_ = null;
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * The RPC protocol versions supported by the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
-       */
-      public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Builder getPeerRpcVersionsBuilder() {
-        
-        onChanged();
-        return getPeerRpcVersionsFieldBuilder().getBuilder();
-      }
-      /**
-       * <pre>
-       * The RPC protocol versions supported by the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
-       */
-      public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersionsOrBuilder getPeerRpcVersionsOrBuilder() {
-        if (peerRpcVersionsBuilder_ != null) {
-          return peerRpcVersionsBuilder_.getMessageOrBuilder();
-        } else {
-          return peerRpcVersions_ == null ?
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.getDefaultInstance() : peerRpcVersions_;
-        }
-      }
-      /**
-       * <pre>
-       * The RPC protocol versions supported by the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 6;</code>
-       */
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Builder, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersionsOrBuilder> 
-          getPeerRpcVersionsFieldBuilder() {
-        if (peerRpcVersionsBuilder_ == null) {
-          peerRpcVersionsBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Builder, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersionsOrBuilder>(
-                  getPeerRpcVersions(),
-                  getParentForChildren(),
-                  isClean());
-          peerRpcVersions_ = null;
-        }
-        return peerRpcVersionsBuilder_;
-      }
-
-      private com.google.protobuf.MapField<
-          java.lang.String, java.lang.String> peerAttributes_;
-      private com.google.protobuf.MapField<java.lang.String, java.lang.String>
-      internalGetPeerAttributes() {
-        if (peerAttributes_ == null) {
-          return com.google.protobuf.MapField.emptyMapField(
-              PeerAttributesDefaultEntryHolder.defaultEntry);
-        }
-        return peerAttributes_;
-      }
-      private com.google.protobuf.MapField<java.lang.String, java.lang.String>
-      internalGetMutablePeerAttributes() {
-        onChanged();;
-        if (peerAttributes_ == null) {
-          peerAttributes_ = com.google.protobuf.MapField.newMapField(
-              PeerAttributesDefaultEntryHolder.defaultEntry);
-        }
-        if (!peerAttributes_.isMutable()) {
-          peerAttributes_ = peerAttributes_.copy();
-        }
-        return peerAttributes_;
-      }
-
-      public int getPeerAttributesCount() {
-        return internalGetPeerAttributes().getMap().size();
-      }
-      /**
-       * <pre>
-       * Additional attributes of the peer.
-       * </pre>
-       *
-       * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
-       */
-
-      public boolean containsPeerAttributes(
-          java.lang.String key) {
-        if (key == null) { throw new java.lang.NullPointerException(); }
-        return internalGetPeerAttributes().getMap().containsKey(key);
-      }
-      /**
-       * Use {@link #getPeerAttributesMap()} instead.
-       */
-      @java.lang.Deprecated
-      public java.util.Map<java.lang.String, java.lang.String> getPeerAttributes() {
-        return getPeerAttributesMap();
-      }
-      /**
-       * <pre>
-       * Additional attributes of the peer.
-       * </pre>
-       *
-       * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
-       */
-
-      public java.util.Map<java.lang.String, java.lang.String> getPeerAttributesMap() {
-        return internalGetPeerAttributes().getMap();
-      }
-      /**
-       * <pre>
-       * Additional attributes of the peer.
-       * </pre>
-       *
-       * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
-       */
-
-      public java.lang.String getPeerAttributesOrDefault(
-          java.lang.String key,
-          java.lang.String defaultValue) {
-        if (key == null) { throw new java.lang.NullPointerException(); }
-        java.util.Map<java.lang.String, java.lang.String> map =
-            internalGetPeerAttributes().getMap();
-        return map.containsKey(key) ? map.get(key) : defaultValue;
-      }
-      /**
-       * <pre>
-       * Additional attributes of the peer.
-       * </pre>
-       *
-       * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
-       */
-
-      public java.lang.String getPeerAttributesOrThrow(
-          java.lang.String key) {
-        if (key == null) { throw new java.lang.NullPointerException(); }
-        java.util.Map<java.lang.String, java.lang.String> map =
-            internalGetPeerAttributes().getMap();
-        if (!map.containsKey(key)) {
-          throw new java.lang.IllegalArgumentException();
-        }
-        return map.get(key);
-      }
-
-      public Builder clearPeerAttributes() {
-        internalGetMutablePeerAttributes().getMutableMap()
-            .clear();
-        return this;
-      }
-      /**
-       * <pre>
-       * Additional attributes of the peer.
-       * </pre>
-       *
-       * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
-       */
-
-      public Builder removePeerAttributes(
-          java.lang.String key) {
-        if (key == null) { throw new java.lang.NullPointerException(); }
-        internalGetMutablePeerAttributes().getMutableMap()
-            .remove(key);
-        return this;
-      }
-      /**
-       * Use alternate mutation accessors instead.
-       */
-      @java.lang.Deprecated
-      public java.util.Map<java.lang.String, java.lang.String>
-      getMutablePeerAttributes() {
-        return internalGetMutablePeerAttributes().getMutableMap();
-      }
-      /**
-       * <pre>
-       * Additional attributes of the peer.
-       * </pre>
-       *
-       * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
-       */
-      public Builder putPeerAttributes(
-          java.lang.String key,
-          java.lang.String value) {
-        if (key == null) { throw new java.lang.NullPointerException(); }
-        if (value == null) { throw new java.lang.NullPointerException(); }
-        internalGetMutablePeerAttributes().getMutableMap()
-            .put(key, value);
-        return this;
-      }
-      /**
-       * <pre>
-       * Additional attributes of the peer.
-       * </pre>
-       *
-       * <code>map&lt;string, string&gt; peer_attributes = 7;</code>
-       */
-
-      public Builder putAllPeerAttributes(
-          java.util.Map<java.lang.String, java.lang.String> values) {
-        internalGetMutablePeerAttributes().getMutableMap()
-            .putAll(values);
-        return this;
-      }
-      public final Builder setUnknownFields(
-          final com.google.protobuf.UnknownFieldSet unknownFields) {
-        return super.setUnknownFieldsProto3(unknownFields);
-      }
-
-      public final Builder mergeUnknownFields(
-          final com.google.protobuf.UnknownFieldSet unknownFields) {
-        return super.mergeUnknownFields(unknownFields);
-      }
-
-
-      // @@protoc_insertion_point(builder_scope:grpc.gcp.AltsContext)
-    }
-
-    // @@protoc_insertion_point(class_scope:grpc.gcp.AltsContext)
-    private static final io.grpc.alts.internal.Altscontext.AltsContext DEFAULT_INSTANCE;
-    static {
-      DEFAULT_INSTANCE = new io.grpc.alts.internal.Altscontext.AltsContext();
-    }
-
-    public static io.grpc.alts.internal.Altscontext.AltsContext getDefaultInstance() {
-      return DEFAULT_INSTANCE;
-    }
-
-    private static final com.google.protobuf.Parser<AltsContext>
-        PARSER = new com.google.protobuf.AbstractParser<AltsContext>() {
-      public AltsContext parsePartialFrom(
-          com.google.protobuf.CodedInputStream input,
-          com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-          throws com.google.protobuf.InvalidProtocolBufferException {
-        return new AltsContext(input, extensionRegistry);
-      }
-    };
-
-    public static com.google.protobuf.Parser<AltsContext> parser() {
-      return PARSER;
-    }
-
-    @java.lang.Override
-    public com.google.protobuf.Parser<AltsContext> getParserForType() {
-      return PARSER;
-    }
-
-    public io.grpc.alts.internal.Altscontext.AltsContext getDefaultInstanceForType() {
-      return DEFAULT_INSTANCE;
-    }
-
-  }
-
-  private static final com.google.protobuf.Descriptors.Descriptor
-    internal_static_grpc_gcp_AltsContext_descriptor;
-  private static final 
-    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
-      internal_static_grpc_gcp_AltsContext_fieldAccessorTable;
-  private static final com.google.protobuf.Descriptors.Descriptor
-    internal_static_grpc_gcp_AltsContext_PeerAttributesEntry_descriptor;
-  private static final 
-    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
-      internal_static_grpc_gcp_AltsContext_PeerAttributesEntry_fieldAccessorTable;
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-  public static com.google.protobuf.Descriptors.FileDescriptor
-      getDescriptor() {
-    return descriptor;
-  }
-  private static  com.google.protobuf.Descriptors.FileDescriptor
-      descriptor;
-  static {
-    java.lang.String[] descriptorData = {
-      "\n\032grpc/gcp/altscontext.proto\022\010grpc.gcp\032(" +
-      "grpc/gcp/transport_security_common.proto" +
-      "\"\347\002\n\013AltsContext\022\034\n\024application_protocol" +
-      "\030\001 \001(\t\022\027\n\017record_protocol\030\002 \001(\t\022/\n\016secur" +
-      "ity_level\030\003 \001(\0162\027.grpc.gcp.SecurityLevel" +
-      "\022\034\n\024peer_service_account\030\004 \001(\t\022\035\n\025local_" +
-      "service_account\030\005 \001(\t\0228\n\021peer_rpc_versio" +
-      "ns\030\006 \001(\0132\035.grpc.gcp.RpcProtocolVersions\022" +
-      "B\n\017peer_attributes\030\007 \003(\0132).grpc.gcp.Alts" +
-      "Context.PeerAttributesEntry\0325\n\023PeerAttri" +
-      "butesEntry\022\013\n\003key\030\001 \001(\t\022\r\n\005value\030\002 \001(\t:\002" +
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-        }, assigner);
-    internal_static_grpc_gcp_AltsContext_descriptor =
-      getDescriptor().getMessageTypes().get(0);
-    internal_static_grpc_gcp_AltsContext_fieldAccessorTable = new
-      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
-        internal_static_grpc_gcp_AltsContext_descriptor,
-        new java.lang.String[] { "ApplicationProtocol", "RecordProtocol", "SecurityLevel", "PeerServiceAccount", "LocalServiceAccount", "PeerRpcVersions", "PeerAttributes", });
-    internal_static_grpc_gcp_AltsContext_PeerAttributesEntry_descriptor =
-      internal_static_grpc_gcp_AltsContext_descriptor.getNestedTypes().get(0);
-    internal_static_grpc_gcp_AltsContext_PeerAttributesEntry_fieldAccessorTable = new
-      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
-        internal_static_grpc_gcp_AltsContext_PeerAttributesEntry_descriptor,
-        new java.lang.String[] { "Key", "Value", });
-    io.grpc.alts.internal.TransportSecurityCommon.getDescriptor();
-  }
-
-  // @@protoc_insertion_point(outer_class_scope)
-}
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/Endpoint.java b/alts/src/generated/main/java/io/grpc/alts/internal/Endpoint.java
new file mode 100644
index 0000000000..4d5f08d413
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/Endpoint.java
@@ -0,0 +1,736 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+/**
+ * Protobuf type {@code grpc.gcp.Endpoint}
+ */
+public  final class Endpoint extends
+    com.google.protobuf.GeneratedMessageV3 implements
+    // @@protoc_insertion_point(message_implements:grpc.gcp.Endpoint)
+    EndpointOrBuilder {
+private static final long serialVersionUID = 0L;
+  // Use Endpoint.newBuilder() to construct.
+  private Endpoint(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
+    super(builder);
+  }
+  private Endpoint() {
+    ipAddress_ = "";
+    port_ = 0;
+    protocol_ = 0;
+  }
+
+  @java.lang.Override
+  public final com.google.protobuf.UnknownFieldSet
+  getUnknownFields() {
+    return this.unknownFields;
+  }
+  private Endpoint(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    this();
+    if (extensionRegistry == null) {
+      throw new java.lang.NullPointerException();
+    }
+    int mutable_bitField0_ = 0;
+    com.google.protobuf.UnknownFieldSet.Builder unknownFields =
+        com.google.protobuf.UnknownFieldSet.newBuilder();
+    try {
+      boolean done = false;
+      while (!done) {
+        int tag = input.readTag();
+        switch (tag) {
+          case 0:
+            done = true;
+            break;
+          default: {
+            if (!parseUnknownFieldProto3(
+                input, unknownFields, extensionRegistry, tag)) {
+              done = true;
+            }
+            break;
+          }
+          case 10: {
+            java.lang.String s = input.readStringRequireUtf8();
+
+            ipAddress_ = s;
+            break;
+          }
+          case 16: {
+
+            port_ = input.readInt32();
+            break;
+          }
+          case 24: {
+            int rawValue = input.readEnum();
+
+            protocol_ = rawValue;
+            break;
+          }
+        }
+      }
+    } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+      throw e.setUnfinishedMessage(this);
+    } catch (java.io.IOException e) {
+      throw new com.google.protobuf.InvalidProtocolBufferException(
+          e).setUnfinishedMessage(this);
+    } finally {
+      this.unknownFields = unknownFields.build();
+      makeExtensionsImmutable();
+    }
+  }
+  public static final com.google.protobuf.Descriptors.Descriptor
+      getDescriptor() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_Endpoint_descriptor;
+  }
+
+  protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internalGetFieldAccessorTable() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_Endpoint_fieldAccessorTable
+        .ensureFieldAccessorsInitialized(
+            io.grpc.alts.internal.Endpoint.class, io.grpc.alts.internal.Endpoint.Builder.class);
+  }
+
+  public static final int IP_ADDRESS_FIELD_NUMBER = 1;
+  private volatile java.lang.Object ipAddress_;
+  /**
+   * <pre>
+   * IP address. It should contain an IPv4 or IPv6 string literal, e.g.
+   * "192.168.0.1" or "2001:db8::1".
+   * </pre>
+   *
+   * <code>string ip_address = 1;</code>
+   */
+  public java.lang.String getIpAddress() {
+    java.lang.Object ref = ipAddress_;
+    if (ref instanceof java.lang.String) {
+      return (java.lang.String) ref;
+    } else {
+      com.google.protobuf.ByteString bs = 
+          (com.google.protobuf.ByteString) ref;
+      java.lang.String s = bs.toStringUtf8();
+      ipAddress_ = s;
+      return s;
+    }
+  }
+  /**
+   * <pre>
+   * IP address. It should contain an IPv4 or IPv6 string literal, e.g.
+   * "192.168.0.1" or "2001:db8::1".
+   * </pre>
+   *
+   * <code>string ip_address = 1;</code>
+   */
+  public com.google.protobuf.ByteString
+      getIpAddressBytes() {
+    java.lang.Object ref = ipAddress_;
+    if (ref instanceof java.lang.String) {
+      com.google.protobuf.ByteString b = 
+          com.google.protobuf.ByteString.copyFromUtf8(
+              (java.lang.String) ref);
+      ipAddress_ = b;
+      return b;
+    } else {
+      return (com.google.protobuf.ByteString) ref;
+    }
+  }
+
+  public static final int PORT_FIELD_NUMBER = 2;
+  private int port_;
+  /**
+   * <pre>
+   * Port number.
+   * </pre>
+   *
+   * <code>int32 port = 2;</code>
+   */
+  public int getPort() {
+    return port_;
+  }
+
+  public static final int PROTOCOL_FIELD_NUMBER = 3;
+  private int protocol_;
+  /**
+   * <pre>
+   * Network protocol (e.g., TCP, UDP) associated with this endpoint.
+   * </pre>
+   *
+   * <code>.grpc.gcp.NetworkProtocol protocol = 3;</code>
+   */
+  public int getProtocolValue() {
+    return protocol_;
+  }
+  /**
+   * <pre>
+   * Network protocol (e.g., TCP, UDP) associated with this endpoint.
+   * </pre>
+   *
+   * <code>.grpc.gcp.NetworkProtocol protocol = 3;</code>
+   */
+  public io.grpc.alts.internal.NetworkProtocol getProtocol() {
+    io.grpc.alts.internal.NetworkProtocol result = io.grpc.alts.internal.NetworkProtocol.valueOf(protocol_);
+    return result == null ? io.grpc.alts.internal.NetworkProtocol.UNRECOGNIZED : result;
+  }
+
+  private byte memoizedIsInitialized = -1;
+  public final boolean isInitialized() {
+    byte isInitialized = memoizedIsInitialized;
+    if (isInitialized == 1) return true;
+    if (isInitialized == 0) return false;
+
+    memoizedIsInitialized = 1;
+    return true;
+  }
+
+  public void writeTo(com.google.protobuf.CodedOutputStream output)
+                      throws java.io.IOException {
+    if (!getIpAddressBytes().isEmpty()) {
+      com.google.protobuf.GeneratedMessageV3.writeString(output, 1, ipAddress_);
+    }
+    if (port_ != 0) {
+      output.writeInt32(2, port_);
+    }
+    if (protocol_ != io.grpc.alts.internal.NetworkProtocol.NETWORK_PROTOCOL_UNSPECIFIED.getNumber()) {
+      output.writeEnum(3, protocol_);
+    }
+    unknownFields.writeTo(output);
+  }
+
+  public int getSerializedSize() {
+    int size = memoizedSize;
+    if (size != -1) return size;
+
+    size = 0;
+    if (!getIpAddressBytes().isEmpty()) {
+      size += com.google.protobuf.GeneratedMessageV3.computeStringSize(1, ipAddress_);
+    }
+    if (port_ != 0) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeInt32Size(2, port_);
+    }
+    if (protocol_ != io.grpc.alts.internal.NetworkProtocol.NETWORK_PROTOCOL_UNSPECIFIED.getNumber()) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeEnumSize(3, protocol_);
+    }
+    size += unknownFields.getSerializedSize();
+    memoizedSize = size;
+    return size;
+  }
+
+  @java.lang.Override
+  public boolean equals(final java.lang.Object obj) {
+    if (obj == this) {
+     return true;
+    }
+    if (!(obj instanceof io.grpc.alts.internal.Endpoint)) {
+      return super.equals(obj);
+    }
+    io.grpc.alts.internal.Endpoint other = (io.grpc.alts.internal.Endpoint) obj;
+
+    boolean result = true;
+    result = result && getIpAddress()
+        .equals(other.getIpAddress());
+    result = result && (getPort()
+        == other.getPort());
+    result = result && protocol_ == other.protocol_;
+    result = result && unknownFields.equals(other.unknownFields);
+    return result;
+  }
+
+  @java.lang.Override
+  public int hashCode() {
+    if (memoizedHashCode != 0) {
+      return memoizedHashCode;
+    }
+    int hash = 41;
+    hash = (19 * hash) + getDescriptor().hashCode();
+    hash = (37 * hash) + IP_ADDRESS_FIELD_NUMBER;
+    hash = (53 * hash) + getIpAddress().hashCode();
+    hash = (37 * hash) + PORT_FIELD_NUMBER;
+    hash = (53 * hash) + getPort();
+    hash = (37 * hash) + PROTOCOL_FIELD_NUMBER;
+    hash = (53 * hash) + protocol_;
+    hash = (29 * hash) + unknownFields.hashCode();
+    memoizedHashCode = hash;
+    return hash;
+  }
+
+  public static io.grpc.alts.internal.Endpoint parseFrom(
+      java.nio.ByteBuffer data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.Endpoint parseFrom(
+      java.nio.ByteBuffer data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.Endpoint parseFrom(
+      com.google.protobuf.ByteString data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.Endpoint parseFrom(
+      com.google.protobuf.ByteString data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.Endpoint parseFrom(byte[] data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.Endpoint parseFrom(
+      byte[] data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.Endpoint parseFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.Endpoint parseFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.Endpoint parseDelimitedFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.Endpoint parseDelimitedFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.Endpoint parseFrom(
+      com.google.protobuf.CodedInputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.Endpoint parseFrom(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+
+  public Builder newBuilderForType() { return newBuilder(); }
+  public static Builder newBuilder() {
+    return DEFAULT_INSTANCE.toBuilder();
+  }
+  public static Builder newBuilder(io.grpc.alts.internal.Endpoint prototype) {
+    return DEFAULT_INSTANCE.toBuilder().mergeFrom(prototype);
+  }
+  public Builder toBuilder() {
+    return this == DEFAULT_INSTANCE
+        ? new Builder() : new Builder().mergeFrom(this);
+  }
+
+  @java.lang.Override
+  protected Builder newBuilderForType(
+      com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+    Builder builder = new Builder(parent);
+    return builder;
+  }
+  /**
+   * Protobuf type {@code grpc.gcp.Endpoint}
+   */
+  public static final class Builder extends
+      com.google.protobuf.GeneratedMessageV3.Builder<Builder> implements
+      // @@protoc_insertion_point(builder_implements:grpc.gcp.Endpoint)
+      io.grpc.alts.internal.EndpointOrBuilder {
+    public static final com.google.protobuf.Descriptors.Descriptor
+        getDescriptor() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_Endpoint_descriptor;
+    }
+
+    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+        internalGetFieldAccessorTable() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_Endpoint_fieldAccessorTable
+          .ensureFieldAccessorsInitialized(
+              io.grpc.alts.internal.Endpoint.class, io.grpc.alts.internal.Endpoint.Builder.class);
+    }
+
+    // Construct using io.grpc.alts.internal.Endpoint.newBuilder()
+    private Builder() {
+      maybeForceBuilderInitialization();
+    }
+
+    private Builder(
+        com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+      super(parent);
+      maybeForceBuilderInitialization();
+    }
+    private void maybeForceBuilderInitialization() {
+      if (com.google.protobuf.GeneratedMessageV3
+              .alwaysUseFieldBuilders) {
+      }
+    }
+    public Builder clear() {
+      super.clear();
+      ipAddress_ = "";
+
+      port_ = 0;
+
+      protocol_ = 0;
+
+      return this;
+    }
+
+    public com.google.protobuf.Descriptors.Descriptor
+        getDescriptorForType() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_Endpoint_descriptor;
+    }
+
+    public io.grpc.alts.internal.Endpoint getDefaultInstanceForType() {
+      return io.grpc.alts.internal.Endpoint.getDefaultInstance();
+    }
+
+    public io.grpc.alts.internal.Endpoint build() {
+      io.grpc.alts.internal.Endpoint result = buildPartial();
+      if (!result.isInitialized()) {
+        throw newUninitializedMessageException(result);
+      }
+      return result;
+    }
+
+    public io.grpc.alts.internal.Endpoint buildPartial() {
+      io.grpc.alts.internal.Endpoint result = new io.grpc.alts.internal.Endpoint(this);
+      result.ipAddress_ = ipAddress_;
+      result.port_ = port_;
+      result.protocol_ = protocol_;
+      onBuilt();
+      return result;
+    }
+
+    public Builder clone() {
+      return (Builder) super.clone();
+    }
+    public Builder setField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.setField(field, value);
+    }
+    public Builder clearField(
+        com.google.protobuf.Descriptors.FieldDescriptor field) {
+      return (Builder) super.clearField(field);
+    }
+    public Builder clearOneof(
+        com.google.protobuf.Descriptors.OneofDescriptor oneof) {
+      return (Builder) super.clearOneof(oneof);
+    }
+    public Builder setRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        int index, java.lang.Object value) {
+      return (Builder) super.setRepeatedField(field, index, value);
+    }
+    public Builder addRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.addRepeatedField(field, value);
+    }
+    public Builder mergeFrom(com.google.protobuf.Message other) {
+      if (other instanceof io.grpc.alts.internal.Endpoint) {
+        return mergeFrom((io.grpc.alts.internal.Endpoint)other);
+      } else {
+        super.mergeFrom(other);
+        return this;
+      }
+    }
+
+    public Builder mergeFrom(io.grpc.alts.internal.Endpoint other) {
+      if (other == io.grpc.alts.internal.Endpoint.getDefaultInstance()) return this;
+      if (!other.getIpAddress().isEmpty()) {
+        ipAddress_ = other.ipAddress_;
+        onChanged();
+      }
+      if (other.getPort() != 0) {
+        setPort(other.getPort());
+      }
+      if (other.protocol_ != 0) {
+        setProtocolValue(other.getProtocolValue());
+      }
+      this.mergeUnknownFields(other.unknownFields);
+      onChanged();
+      return this;
+    }
+
+    public final boolean isInitialized() {
+      return true;
+    }
+
+    public Builder mergeFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      io.grpc.alts.internal.Endpoint parsedMessage = null;
+      try {
+        parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);
+      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+        parsedMessage = (io.grpc.alts.internal.Endpoint) e.getUnfinishedMessage();
+        throw e.unwrapIOException();
+      } finally {
+        if (parsedMessage != null) {
+          mergeFrom(parsedMessage);
+        }
+      }
+      return this;
+    }
+
+    private java.lang.Object ipAddress_ = "";
+    /**
+     * <pre>
+     * IP address. It should contain an IPv4 or IPv6 string literal, e.g.
+     * "192.168.0.1" or "2001:db8::1".
+     * </pre>
+     *
+     * <code>string ip_address = 1;</code>
+     */
+    public java.lang.String getIpAddress() {
+      java.lang.Object ref = ipAddress_;
+      if (!(ref instanceof java.lang.String)) {
+        com.google.protobuf.ByteString bs =
+            (com.google.protobuf.ByteString) ref;
+        java.lang.String s = bs.toStringUtf8();
+        ipAddress_ = s;
+        return s;
+      } else {
+        return (java.lang.String) ref;
+      }
+    }
+    /**
+     * <pre>
+     * IP address. It should contain an IPv4 or IPv6 string literal, e.g.
+     * "192.168.0.1" or "2001:db8::1".
+     * </pre>
+     *
+     * <code>string ip_address = 1;</code>
+     */
+    public com.google.protobuf.ByteString
+        getIpAddressBytes() {
+      java.lang.Object ref = ipAddress_;
+      if (ref instanceof String) {
+        com.google.protobuf.ByteString b = 
+            com.google.protobuf.ByteString.copyFromUtf8(
+                (java.lang.String) ref);
+        ipAddress_ = b;
+        return b;
+      } else {
+        return (com.google.protobuf.ByteString) ref;
+      }
+    }
+    /**
+     * <pre>
+     * IP address. It should contain an IPv4 or IPv6 string literal, e.g.
+     * "192.168.0.1" or "2001:db8::1".
+     * </pre>
+     *
+     * <code>string ip_address = 1;</code>
+     */
+    public Builder setIpAddress(
+        java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  
+      ipAddress_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * IP address. It should contain an IPv4 or IPv6 string literal, e.g.
+     * "192.168.0.1" or "2001:db8::1".
+     * </pre>
+     *
+     * <code>string ip_address = 1;</code>
+     */
+    public Builder clearIpAddress() {
+      
+      ipAddress_ = getDefaultInstance().getIpAddress();
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * IP address. It should contain an IPv4 or IPv6 string literal, e.g.
+     * "192.168.0.1" or "2001:db8::1".
+     * </pre>
+     *
+     * <code>string ip_address = 1;</code>
+     */
+    public Builder setIpAddressBytes(
+        com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  checkByteStringIsUtf8(value);
+      
+      ipAddress_ = value;
+      onChanged();
+      return this;
+    }
+
+    private int port_ ;
+    /**
+     * <pre>
+     * Port number.
+     * </pre>
+     *
+     * <code>int32 port = 2;</code>
+     */
+    public int getPort() {
+      return port_;
+    }
+    /**
+     * <pre>
+     * Port number.
+     * </pre>
+     *
+     * <code>int32 port = 2;</code>
+     */
+    public Builder setPort(int value) {
+      
+      port_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * Port number.
+     * </pre>
+     *
+     * <code>int32 port = 2;</code>
+     */
+    public Builder clearPort() {
+      
+      port_ = 0;
+      onChanged();
+      return this;
+    }
+
+    private int protocol_ = 0;
+    /**
+     * <pre>
+     * Network protocol (e.g., TCP, UDP) associated with this endpoint.
+     * </pre>
+     *
+     * <code>.grpc.gcp.NetworkProtocol protocol = 3;</code>
+     */
+    public int getProtocolValue() {
+      return protocol_;
+    }
+    /**
+     * <pre>
+     * Network protocol (e.g., TCP, UDP) associated with this endpoint.
+     * </pre>
+     *
+     * <code>.grpc.gcp.NetworkProtocol protocol = 3;</code>
+     */
+    public Builder setProtocolValue(int value) {
+      protocol_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * Network protocol (e.g., TCP, UDP) associated with this endpoint.
+     * </pre>
+     *
+     * <code>.grpc.gcp.NetworkProtocol protocol = 3;</code>
+     */
+    public io.grpc.alts.internal.NetworkProtocol getProtocol() {
+      io.grpc.alts.internal.NetworkProtocol result = io.grpc.alts.internal.NetworkProtocol.valueOf(protocol_);
+      return result == null ? io.grpc.alts.internal.NetworkProtocol.UNRECOGNIZED : result;
+    }
+    /**
+     * <pre>
+     * Network protocol (e.g., TCP, UDP) associated with this endpoint.
+     * </pre>
+     *
+     * <code>.grpc.gcp.NetworkProtocol protocol = 3;</code>
+     */
+    public Builder setProtocol(io.grpc.alts.internal.NetworkProtocol value) {
+      if (value == null) {
+        throw new NullPointerException();
+      }
+      
+      protocol_ = value.getNumber();
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * Network protocol (e.g., TCP, UDP) associated with this endpoint.
+     * </pre>
+     *
+     * <code>.grpc.gcp.NetworkProtocol protocol = 3;</code>
+     */
+    public Builder clearProtocol() {
+      
+      protocol_ = 0;
+      onChanged();
+      return this;
+    }
+    public final Builder setUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.setUnknownFieldsProto3(unknownFields);
+    }
+
+    public final Builder mergeUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.mergeUnknownFields(unknownFields);
+    }
+
+
+    // @@protoc_insertion_point(builder_scope:grpc.gcp.Endpoint)
+  }
+
+  // @@protoc_insertion_point(class_scope:grpc.gcp.Endpoint)
+  private static final io.grpc.alts.internal.Endpoint DEFAULT_INSTANCE;
+  static {
+    DEFAULT_INSTANCE = new io.grpc.alts.internal.Endpoint();
+  }
+
+  public static io.grpc.alts.internal.Endpoint getDefaultInstance() {
+    return DEFAULT_INSTANCE;
+  }
+
+  private static final com.google.protobuf.Parser<Endpoint>
+      PARSER = new com.google.protobuf.AbstractParser<Endpoint>() {
+    public Endpoint parsePartialFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return new Endpoint(input, extensionRegistry);
+    }
+  };
+
+  public static com.google.protobuf.Parser<Endpoint> parser() {
+    return PARSER;
+  }
+
+  @java.lang.Override
+  public com.google.protobuf.Parser<Endpoint> getParserForType() {
+    return PARSER;
+  }
+
+  public io.grpc.alts.internal.Endpoint getDefaultInstanceForType() {
+    return DEFAULT_INSTANCE;
+  }
+
+}
+
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/EndpointOrBuilder.java b/alts/src/generated/main/java/io/grpc/alts/internal/EndpointOrBuilder.java
new file mode 100644
index 0000000000..25ae0fe820
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/EndpointOrBuilder.java
@@ -0,0 +1,55 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+public interface EndpointOrBuilder extends
+    // @@protoc_insertion_point(interface_extends:grpc.gcp.Endpoint)
+    com.google.protobuf.MessageOrBuilder {
+
+  /**
+   * <pre>
+   * IP address. It should contain an IPv4 or IPv6 string literal, e.g.
+   * "192.168.0.1" or "2001:db8::1".
+   * </pre>
+   *
+   * <code>string ip_address = 1;</code>
+   */
+  java.lang.String getIpAddress();
+  /**
+   * <pre>
+   * IP address. It should contain an IPv4 or IPv6 string literal, e.g.
+   * "192.168.0.1" or "2001:db8::1".
+   * </pre>
+   *
+   * <code>string ip_address = 1;</code>
+   */
+  com.google.protobuf.ByteString
+      getIpAddressBytes();
+
+  /**
+   * <pre>
+   * Port number.
+   * </pre>
+   *
+   * <code>int32 port = 2;</code>
+   */
+  int getPort();
+
+  /**
+   * <pre>
+   * Network protocol (e.g., TCP, UDP) associated with this endpoint.
+   * </pre>
+   *
+   * <code>.grpc.gcp.NetworkProtocol protocol = 3;</code>
+   */
+  int getProtocolValue();
+  /**
+   * <pre>
+   * Network protocol (e.g., TCP, UDP) associated with this endpoint.
+   * </pre>
+   *
+   * <code>.grpc.gcp.NetworkProtocol protocol = 3;</code>
+   */
+  io.grpc.alts.internal.NetworkProtocol getProtocol();
+}
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/HandshakeProtocol.java b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakeProtocol.java
new file mode 100644
index 0000000000..6be49fe03e
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakeProtocol.java
@@ -0,0 +1,136 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+/**
+ * Protobuf enum {@code grpc.gcp.HandshakeProtocol}
+ */
+public enum HandshakeProtocol
+    implements com.google.protobuf.ProtocolMessageEnum {
+  /**
+   * <pre>
+   * Default value.
+   * </pre>
+   *
+   * <code>HANDSHAKE_PROTOCOL_UNSPECIFIED = 0;</code>
+   */
+  HANDSHAKE_PROTOCOL_UNSPECIFIED(0),
+  /**
+   * <pre>
+   * TLS handshake protocol.
+   * </pre>
+   *
+   * <code>TLS = 1;</code>
+   */
+  TLS(1),
+  /**
+   * <pre>
+   * Application Layer Transport Security handshake protocol.
+   * </pre>
+   *
+   * <code>ALTS = 2;</code>
+   */
+  ALTS(2),
+  UNRECOGNIZED(-1),
+  ;
+
+  /**
+   * <pre>
+   * Default value.
+   * </pre>
+   *
+   * <code>HANDSHAKE_PROTOCOL_UNSPECIFIED = 0;</code>
+   */
+  public static final int HANDSHAKE_PROTOCOL_UNSPECIFIED_VALUE = 0;
+  /**
+   * <pre>
+   * TLS handshake protocol.
+   * </pre>
+   *
+   * <code>TLS = 1;</code>
+   */
+  public static final int TLS_VALUE = 1;
+  /**
+   * <pre>
+   * Application Layer Transport Security handshake protocol.
+   * </pre>
+   *
+   * <code>ALTS = 2;</code>
+   */
+  public static final int ALTS_VALUE = 2;
+
+
+  public final int getNumber() {
+    if (this == UNRECOGNIZED) {
+      throw new java.lang.IllegalArgumentException(
+          "Can't get the number of an unknown enum value.");
+    }
+    return value;
+  }
+
+  /**
+   * @deprecated Use {@link #forNumber(int)} instead.
+   */
+  @java.lang.Deprecated
+  public static HandshakeProtocol valueOf(int value) {
+    return forNumber(value);
+  }
+
+  public static HandshakeProtocol forNumber(int value) {
+    switch (value) {
+      case 0: return HANDSHAKE_PROTOCOL_UNSPECIFIED;
+      case 1: return TLS;
+      case 2: return ALTS;
+      default: return null;
+    }
+  }
+
+  public static com.google.protobuf.Internal.EnumLiteMap<HandshakeProtocol>
+      internalGetValueMap() {
+    return internalValueMap;
+  }
+  private static final com.google.protobuf.Internal.EnumLiteMap<
+      HandshakeProtocol> internalValueMap =
+        new com.google.protobuf.Internal.EnumLiteMap<HandshakeProtocol>() {
+          public HandshakeProtocol findValueByNumber(int number) {
+            return HandshakeProtocol.forNumber(number);
+          }
+        };
+
+  public final com.google.protobuf.Descriptors.EnumValueDescriptor
+      getValueDescriptor() {
+    return getDescriptor().getValues().get(ordinal());
+  }
+  public final com.google.protobuf.Descriptors.EnumDescriptor
+      getDescriptorForType() {
+    return getDescriptor();
+  }
+  public static final com.google.protobuf.Descriptors.EnumDescriptor
+      getDescriptor() {
+    return io.grpc.alts.internal.HandshakerProto.getDescriptor().getEnumTypes().get(0);
+  }
+
+  private static final HandshakeProtocol[] VALUES = values();
+
+  public static HandshakeProtocol valueOf(
+      com.google.protobuf.Descriptors.EnumValueDescriptor desc) {
+    if (desc.getType() != getDescriptor()) {
+      throw new java.lang.IllegalArgumentException(
+        "EnumValueDescriptor is not for this type.");
+    }
+    if (desc.getIndex() == -1) {
+      return UNRECOGNIZED;
+    }
+    return VALUES[desc.getIndex()];
+  }
+
+  private final int value;
+
+  private HandshakeProtocol(int value) {
+    this.value = value;
+  }
+
+  // @@protoc_insertion_point(enum_scope:grpc.gcp.HandshakeProtocol)
+}
+
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/Handshaker.java b/alts/src/generated/main/java/io/grpc/alts/internal/Handshaker.java
deleted file mode 100644
index 2daa8c14fc..0000000000
--- a/alts/src/generated/main/java/io/grpc/alts/internal/Handshaker.java
+++ /dev/null
@@ -1,13709 +0,0 @@
-// Generated by the protocol buffer compiler.  DO NOT EDIT!
-// source: grpc/gcp/handshaker.proto
-
-package io.grpc.alts.internal;
-
-public final class Handshaker {
-  private Handshaker() {}
-  public static void registerAllExtensions(
-      com.google.protobuf.ExtensionRegistryLite registry) {
-  }
-
-  public static void registerAllExtensions(
-      com.google.protobuf.ExtensionRegistry registry) {
-    registerAllExtensions(
-        (com.google.protobuf.ExtensionRegistryLite) registry);
-  }
-  /**
-   * Protobuf enum {@code grpc.gcp.HandshakeProtocol}
-   */
-  public enum HandshakeProtocol
-      implements com.google.protobuf.ProtocolMessageEnum {
-    /**
-     * <pre>
-     * Default value.
-     * </pre>
-     *
-     * <code>HANDSHAKE_PROTOCOL_UNSPECIFIED = 0;</code>
-     */
-    HANDSHAKE_PROTOCOL_UNSPECIFIED(0),
-    /**
-     * <pre>
-     * TLS handshake protocol.
-     * </pre>
-     *
-     * <code>TLS = 1;</code>
-     */
-    TLS(1),
-    /**
-     * <pre>
-     * Application Layer Transport Security handshake protocol.
-     * </pre>
-     *
-     * <code>ALTS = 2;</code>
-     */
-    ALTS(2),
-    UNRECOGNIZED(-1),
-    ;
-
-    /**
-     * <pre>
-     * Default value.
-     * </pre>
-     *
-     * <code>HANDSHAKE_PROTOCOL_UNSPECIFIED = 0;</code>
-     */
-    public static final int HANDSHAKE_PROTOCOL_UNSPECIFIED_VALUE = 0;
-    /**
-     * <pre>
-     * TLS handshake protocol.
-     * </pre>
-     *
-     * <code>TLS = 1;</code>
-     */
-    public static final int TLS_VALUE = 1;
-    /**
-     * <pre>
-     * Application Layer Transport Security handshake protocol.
-     * </pre>
-     *
-     * <code>ALTS = 2;</code>
-     */
-    public static final int ALTS_VALUE = 2;
-
-
-    public final int getNumber() {
-      if (this == UNRECOGNIZED) {
-        throw new java.lang.IllegalArgumentException(
-            "Can't get the number of an unknown enum value.");
-      }
-      return value;
-    }
-
-    /**
-     * @deprecated Use {@link #forNumber(int)} instead.
-     */
-    @java.lang.Deprecated
-    public static HandshakeProtocol valueOf(int value) {
-      return forNumber(value);
-    }
-
-    public static HandshakeProtocol forNumber(int value) {
-      switch (value) {
-        case 0: return HANDSHAKE_PROTOCOL_UNSPECIFIED;
-        case 1: return TLS;
-        case 2: return ALTS;
-        default: return null;
-      }
-    }
-
-    public static com.google.protobuf.Internal.EnumLiteMap<HandshakeProtocol>
-        internalGetValueMap() {
-      return internalValueMap;
-    }
-    private static final com.google.protobuf.Internal.EnumLiteMap<
-        HandshakeProtocol> internalValueMap =
-          new com.google.protobuf.Internal.EnumLiteMap<HandshakeProtocol>() {
-            public HandshakeProtocol findValueByNumber(int number) {
-              return HandshakeProtocol.forNumber(number);
-            }
-          };
-
-    public final com.google.protobuf.Descriptors.EnumValueDescriptor
-        getValueDescriptor() {
-      return getDescriptor().getValues().get(ordinal());
-    }
-    public final com.google.protobuf.Descriptors.EnumDescriptor
-        getDescriptorForType() {
-      return getDescriptor();
-    }
-    public static final com.google.protobuf.Descriptors.EnumDescriptor
-        getDescriptor() {
-      return io.grpc.alts.internal.Handshaker.getDescriptor().getEnumTypes().get(0);
-    }
-
-    private static final HandshakeProtocol[] VALUES = values();
-
-    public static HandshakeProtocol valueOf(
-        com.google.protobuf.Descriptors.EnumValueDescriptor desc) {
-      if (desc.getType() != getDescriptor()) {
-        throw new java.lang.IllegalArgumentException(
-          "EnumValueDescriptor is not for this type.");
-      }
-      if (desc.getIndex() == -1) {
-        return UNRECOGNIZED;
-      }
-      return VALUES[desc.getIndex()];
-    }
-
-    private final int value;
-
-    private HandshakeProtocol(int value) {
-      this.value = value;
-    }
-
-    // @@protoc_insertion_point(enum_scope:grpc.gcp.HandshakeProtocol)
-  }
-
-  /**
-   * Protobuf enum {@code grpc.gcp.NetworkProtocol}
-   */
-  public enum NetworkProtocol
-      implements com.google.protobuf.ProtocolMessageEnum {
-    /**
-     * <code>NETWORK_PROTOCOL_UNSPECIFIED = 0;</code>
-     */
-    NETWORK_PROTOCOL_UNSPECIFIED(0),
-    /**
-     * <code>TCP = 1;</code>
-     */
-    TCP(1),
-    /**
-     * <code>UDP = 2;</code>
-     */
-    UDP(2),
-    UNRECOGNIZED(-1),
-    ;
-
-    /**
-     * <code>NETWORK_PROTOCOL_UNSPECIFIED = 0;</code>
-     */
-    public static final int NETWORK_PROTOCOL_UNSPECIFIED_VALUE = 0;
-    /**
-     * <code>TCP = 1;</code>
-     */
-    public static final int TCP_VALUE = 1;
-    /**
-     * <code>UDP = 2;</code>
-     */
-    public static final int UDP_VALUE = 2;
-
-
-    public final int getNumber() {
-      if (this == UNRECOGNIZED) {
-        throw new java.lang.IllegalArgumentException(
-            "Can't get the number of an unknown enum value.");
-      }
-      return value;
-    }
-
-    /**
-     * @deprecated Use {@link #forNumber(int)} instead.
-     */
-    @java.lang.Deprecated
-    public static NetworkProtocol valueOf(int value) {
-      return forNumber(value);
-    }
-
-    public static NetworkProtocol forNumber(int value) {
-      switch (value) {
-        case 0: return NETWORK_PROTOCOL_UNSPECIFIED;
-        case 1: return TCP;
-        case 2: return UDP;
-        default: return null;
-      }
-    }
-
-    public static com.google.protobuf.Internal.EnumLiteMap<NetworkProtocol>
-        internalGetValueMap() {
-      return internalValueMap;
-    }
-    private static final com.google.protobuf.Internal.EnumLiteMap<
-        NetworkProtocol> internalValueMap =
-          new com.google.protobuf.Internal.EnumLiteMap<NetworkProtocol>() {
-            public NetworkProtocol findValueByNumber(int number) {
-              return NetworkProtocol.forNumber(number);
-            }
-          };
-
-    public final com.google.protobuf.Descriptors.EnumValueDescriptor
-        getValueDescriptor() {
-      return getDescriptor().getValues().get(ordinal());
-    }
-    public final com.google.protobuf.Descriptors.EnumDescriptor
-        getDescriptorForType() {
-      return getDescriptor();
-    }
-    public static final com.google.protobuf.Descriptors.EnumDescriptor
-        getDescriptor() {
-      return io.grpc.alts.internal.Handshaker.getDescriptor().getEnumTypes().get(1);
-    }
-
-    private static final NetworkProtocol[] VALUES = values();
-
-    public static NetworkProtocol valueOf(
-        com.google.protobuf.Descriptors.EnumValueDescriptor desc) {
-      if (desc.getType() != getDescriptor()) {
-        throw new java.lang.IllegalArgumentException(
-          "EnumValueDescriptor is not for this type.");
-      }
-      if (desc.getIndex() == -1) {
-        return UNRECOGNIZED;
-      }
-      return VALUES[desc.getIndex()];
-    }
-
-    private final int value;
-
-    private NetworkProtocol(int value) {
-      this.value = value;
-    }
-
-    // @@protoc_insertion_point(enum_scope:grpc.gcp.NetworkProtocol)
-  }
-
-  public interface EndpointOrBuilder extends
-      // @@protoc_insertion_point(interface_extends:grpc.gcp.Endpoint)
-      com.google.protobuf.MessageOrBuilder {
-
-    /**
-     * <pre>
-     * IP address. It should contain an IPv4 or IPv6 string literal, e.g.
-     * "192.168.0.1" or "2001:db8::1".
-     * </pre>
-     *
-     * <code>string ip_address = 1;</code>
-     */
-    java.lang.String getIpAddress();
-    /**
-     * <pre>
-     * IP address. It should contain an IPv4 or IPv6 string literal, e.g.
-     * "192.168.0.1" or "2001:db8::1".
-     * </pre>
-     *
-     * <code>string ip_address = 1;</code>
-     */
-    com.google.protobuf.ByteString
-        getIpAddressBytes();
-
-    /**
-     * <pre>
-     * Port number.
-     * </pre>
-     *
-     * <code>int32 port = 2;</code>
-     */
-    int getPort();
-
-    /**
-     * <pre>
-     * Network protocol (e.g., TCP, UDP) associated with this endpoint.
-     * </pre>
-     *
-     * <code>.grpc.gcp.NetworkProtocol protocol = 3;</code>
-     */
-    int getProtocolValue();
-    /**
-     * <pre>
-     * Network protocol (e.g., TCP, UDP) associated with this endpoint.
-     * </pre>
-     *
-     * <code>.grpc.gcp.NetworkProtocol protocol = 3;</code>
-     */
-    io.grpc.alts.internal.Handshaker.NetworkProtocol getProtocol();
-  }
-  /**
-   * Protobuf type {@code grpc.gcp.Endpoint}
-   */
-  public  static final class Endpoint extends
-      com.google.protobuf.GeneratedMessageV3 implements
-      // @@protoc_insertion_point(message_implements:grpc.gcp.Endpoint)
-      EndpointOrBuilder {
-  private static final long serialVersionUID = 0L;
-    // Use Endpoint.newBuilder() to construct.
-    private Endpoint(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
-      super(builder);
-    }
-    private Endpoint() {
-      ipAddress_ = "";
-      port_ = 0;
-      protocol_ = 0;
-    }
-
-    @java.lang.Override
-    public final com.google.protobuf.UnknownFieldSet
-    getUnknownFields() {
-      return this.unknownFields;
-    }
-    private Endpoint(
-        com.google.protobuf.CodedInputStream input,
-        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-        throws com.google.protobuf.InvalidProtocolBufferException {
-      this();
-      if (extensionRegistry == null) {
-        throw new java.lang.NullPointerException();
-      }
-      int mutable_bitField0_ = 0;
-      com.google.protobuf.UnknownFieldSet.Builder unknownFields =
-          com.google.protobuf.UnknownFieldSet.newBuilder();
-      try {
-        boolean done = false;
-        while (!done) {
-          int tag = input.readTag();
-          switch (tag) {
-            case 0:
-              done = true;
-              break;
-            default: {
-              if (!parseUnknownFieldProto3(
-                  input, unknownFields, extensionRegistry, tag)) {
-                done = true;
-              }
-              break;
-            }
-            case 10: {
-              java.lang.String s = input.readStringRequireUtf8();
-
-              ipAddress_ = s;
-              break;
-            }
-            case 16: {
-
-              port_ = input.readInt32();
-              break;
-            }
-            case 24: {
-              int rawValue = input.readEnum();
-
-              protocol_ = rawValue;
-              break;
-            }
-          }
-        }
-      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
-        throw e.setUnfinishedMessage(this);
-      } catch (java.io.IOException e) {
-        throw new com.google.protobuf.InvalidProtocolBufferException(
-            e).setUnfinishedMessage(this);
-      } finally {
-        this.unknownFields = unknownFields.build();
-        makeExtensionsImmutable();
-      }
-    }
-    public static final com.google.protobuf.Descriptors.Descriptor
-        getDescriptor() {
-      return io.grpc.alts.internal.Handshaker.internal_static_grpc_gcp_Endpoint_descriptor;
-    }
-
-    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
-        internalGetFieldAccessorTable() {
-      return io.grpc.alts.internal.Handshaker.internal_static_grpc_gcp_Endpoint_fieldAccessorTable
-          .ensureFieldAccessorsInitialized(
-              io.grpc.alts.internal.Handshaker.Endpoint.class, io.grpc.alts.internal.Handshaker.Endpoint.Builder.class);
-    }
-
-    public static final int IP_ADDRESS_FIELD_NUMBER = 1;
-    private volatile java.lang.Object ipAddress_;
-    /**
-     * <pre>
-     * IP address. It should contain an IPv4 or IPv6 string literal, e.g.
-     * "192.168.0.1" or "2001:db8::1".
-     * </pre>
-     *
-     * <code>string ip_address = 1;</code>
-     */
-    public java.lang.String getIpAddress() {
-      java.lang.Object ref = ipAddress_;
-      if (ref instanceof java.lang.String) {
-        return (java.lang.String) ref;
-      } else {
-        com.google.protobuf.ByteString bs = 
-            (com.google.protobuf.ByteString) ref;
-        java.lang.String s = bs.toStringUtf8();
-        ipAddress_ = s;
-        return s;
-      }
-    }
-    /**
-     * <pre>
-     * IP address. It should contain an IPv4 or IPv6 string literal, e.g.
-     * "192.168.0.1" or "2001:db8::1".
-     * </pre>
-     *
-     * <code>string ip_address = 1;</code>
-     */
-    public com.google.protobuf.ByteString
-        getIpAddressBytes() {
-      java.lang.Object ref = ipAddress_;
-      if (ref instanceof java.lang.String) {
-        com.google.protobuf.ByteString b = 
-            com.google.protobuf.ByteString.copyFromUtf8(
-                (java.lang.String) ref);
-        ipAddress_ = b;
-        return b;
-      } else {
-        return (com.google.protobuf.ByteString) ref;
-      }
-    }
-
-    public static final int PORT_FIELD_NUMBER = 2;
-    private int port_;
-    /**
-     * <pre>
-     * Port number.
-     * </pre>
-     *
-     * <code>int32 port = 2;</code>
-     */
-    public int getPort() {
-      return port_;
-    }
-
-    public static final int PROTOCOL_FIELD_NUMBER = 3;
-    private int protocol_;
-    /**
-     * <pre>
-     * Network protocol (e.g., TCP, UDP) associated with this endpoint.
-     * </pre>
-     *
-     * <code>.grpc.gcp.NetworkProtocol protocol = 3;</code>
-     */
-    public int getProtocolValue() {
-      return protocol_;
-    }
-    /**
-     * <pre>
-     * Network protocol (e.g., TCP, UDP) associated with this endpoint.
-     * </pre>
-     *
-     * <code>.grpc.gcp.NetworkProtocol protocol = 3;</code>
-     */
-    public io.grpc.alts.internal.Handshaker.NetworkProtocol getProtocol() {
-      io.grpc.alts.internal.Handshaker.NetworkProtocol result = io.grpc.alts.internal.Handshaker.NetworkProtocol.valueOf(protocol_);
-      return result == null ? io.grpc.alts.internal.Handshaker.NetworkProtocol.UNRECOGNIZED : result;
-    }
-
-    private byte memoizedIsInitialized = -1;
-    public final boolean isInitialized() {
-      byte isInitialized = memoizedIsInitialized;
-      if (isInitialized == 1) return true;
-      if (isInitialized == 0) return false;
-
-      memoizedIsInitialized = 1;
-      return true;
-    }
-
-    public void writeTo(com.google.protobuf.CodedOutputStream output)
-                        throws java.io.IOException {
-      if (!getIpAddressBytes().isEmpty()) {
-        com.google.protobuf.GeneratedMessageV3.writeString(output, 1, ipAddress_);
-      }
-      if (port_ != 0) {
-        output.writeInt32(2, port_);
-      }
-      if (protocol_ != io.grpc.alts.internal.Handshaker.NetworkProtocol.NETWORK_PROTOCOL_UNSPECIFIED.getNumber()) {
-        output.writeEnum(3, protocol_);
-      }
-      unknownFields.writeTo(output);
-    }
-
-    public int getSerializedSize() {
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-  identityOneofCase_ = 1;
-        identityOneof_ = value;
-        onChanged();
-        return this;
-      }
-      /**
-       * <pre>
-       * Service account of a connection endpoint.
-       * </pre>
-       *
-       * <code>string service_account = 1;</code>
-       */
-      public Builder clearServiceAccount() {
-        if (identityOneofCase_ == 1) {
-          identityOneofCase_ = 0;
-          identityOneof_ = null;
-          onChanged();
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * Service account of a connection endpoint.
-       * </pre>
-       *
-       * <code>string service_account = 1;</code>
-       */
-      public Builder setServiceAccountBytes(
-          com.google.protobuf.ByteString value) {
-        if (value == null) {
-    throw new NullPointerException();
-  }
-  checkByteStringIsUtf8(value);
-        identityOneofCase_ = 1;
-        identityOneof_ = value;
-        onChanged();
-        return this;
-      }
-
-      /**
-       * <pre>
-       * Hostname of a connection endpoint.
-       * </pre>
-       *
-       * <code>string hostname = 2;</code>
-       */
-      public java.lang.String getHostname() {
-        java.lang.Object ref = "";
-        if (identityOneofCase_ == 2) {
-          ref = identityOneof_;
-        }
-        if (!(ref instanceof java.lang.String)) {
-          com.google.protobuf.ByteString bs =
-              (com.google.protobuf.ByteString) ref;
-          java.lang.String s = bs.toStringUtf8();
-          if (identityOneofCase_ == 2) {
-            identityOneof_ = s;
-          }
-          return s;
-        } else {
-          return (java.lang.String) ref;
-        }
-      }
-      /**
-       * <pre>
-       * Hostname of a connection endpoint.
-       * </pre>
-       *
-       * <code>string hostname = 2;</code>
-       */
-      public com.google.protobuf.ByteString
-          getHostnameBytes() {
-        java.lang.Object ref = "";
-        if (identityOneofCase_ == 2) {
-          ref = identityOneof_;
-        }
-        if (ref instanceof String) {
-          com.google.protobuf.ByteString b = 
-              com.google.protobuf.ByteString.copyFromUtf8(
-                  (java.lang.String) ref);
-          if (identityOneofCase_ == 2) {
-            identityOneof_ = b;
-          }
-          return b;
-        } else {
-          return (com.google.protobuf.ByteString) ref;
-        }
-      }
-      /**
-       * <pre>
-       * Hostname of a connection endpoint.
-       * </pre>
-       *
-       * <code>string hostname = 2;</code>
-       */
-      public Builder setHostname(
-          java.lang.String value) {
-        if (value == null) {
-    throw new NullPointerException();
-  }
-  identityOneofCase_ = 2;
-        identityOneof_ = value;
-        onChanged();
-        return this;
-      }
-      /**
-       * <pre>
-       * Hostname of a connection endpoint.
-       * </pre>
-       *
-       * <code>string hostname = 2;</code>
-       */
-      public Builder clearHostname() {
-        if (identityOneofCase_ == 2) {
-          identityOneofCase_ = 0;
-          identityOneof_ = null;
-          onChanged();
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * Hostname of a connection endpoint.
-       * </pre>
-       *
-       * <code>string hostname = 2;</code>
-       */
-      public Builder setHostnameBytes(
-          com.google.protobuf.ByteString value) {
-        if (value == null) {
-    throw new NullPointerException();
-  }
-  checkByteStringIsUtf8(value);
-        identityOneofCase_ = 2;
-        identityOneof_ = value;
-        onChanged();
-        return this;
-      }
-
-      private com.google.protobuf.MapField<
-          java.lang.String, java.lang.String> attributes_;
-      private com.google.protobuf.MapField<java.lang.String, java.lang.String>
-      internalGetAttributes() {
-        if (attributes_ == null) {
-          return com.google.protobuf.MapField.emptyMapField(
-              AttributesDefaultEntryHolder.defaultEntry);
-        }
-        return attributes_;
-      }
-      private com.google.protobuf.MapField<java.lang.String, java.lang.String>
-      internalGetMutableAttributes() {
-        onChanged();;
-        if (attributes_ == null) {
-          attributes_ = com.google.protobuf.MapField.newMapField(
-              AttributesDefaultEntryHolder.defaultEntry);
-        }
-        if (!attributes_.isMutable()) {
-          attributes_ = attributes_.copy();
-        }
-        return attributes_;
-      }
-
-      public int getAttributesCount() {
-        return internalGetAttributes().getMap().size();
-      }
-      /**
-       * <pre>
-       * Additional attributes of the identity.
-       * </pre>
-       *
-       * <code>map&lt;string, string&gt; attributes = 3;</code>
-       */
-
-      public boolean containsAttributes(
-          java.lang.String key) {
-        if (key == null) { throw new java.lang.NullPointerException(); }
-        return internalGetAttributes().getMap().containsKey(key);
-      }
-      /**
-       * Use {@link #getAttributesMap()} instead.
-       */
-      @java.lang.Deprecated
-      public java.util.Map<java.lang.String, java.lang.String> getAttributes() {
-        return getAttributesMap();
-      }
-      /**
-       * <pre>
-       * Additional attributes of the identity.
-       * </pre>
-       *
-       * <code>map&lt;string, string&gt; attributes = 3;</code>
-       */
-
-      public java.util.Map<java.lang.String, java.lang.String> getAttributesMap() {
-        return internalGetAttributes().getMap();
-      }
-      /**
-       * <pre>
-       * Additional attributes of the identity.
-       * </pre>
-       *
-       * <code>map&lt;string, string&gt; attributes = 3;</code>
-       */
-
-      public java.lang.String getAttributesOrDefault(
-          java.lang.String key,
-          java.lang.String defaultValue) {
-        if (key == null) { throw new java.lang.NullPointerException(); }
-        java.util.Map<java.lang.String, java.lang.String> map =
-            internalGetAttributes().getMap();
-        return map.containsKey(key) ? map.get(key) : defaultValue;
-      }
-      /**
-       * <pre>
-       * Additional attributes of the identity.
-       * </pre>
-       *
-       * <code>map&lt;string, string&gt; attributes = 3;</code>
-       */
-
-      public java.lang.String getAttributesOrThrow(
-          java.lang.String key) {
-        if (key == null) { throw new java.lang.NullPointerException(); }
-        java.util.Map<java.lang.String, java.lang.String> map =
-            internalGetAttributes().getMap();
-        if (!map.containsKey(key)) {
-          throw new java.lang.IllegalArgumentException();
-        }
-        return map.get(key);
-      }
-
-      public Builder clearAttributes() {
-        internalGetMutableAttributes().getMutableMap()
-            .clear();
-        return this;
-      }
-      /**
-       * <pre>
-       * Additional attributes of the identity.
-       * </pre>
-       *
-       * <code>map&lt;string, string&gt; attributes = 3;</code>
-       */
-
-      public Builder removeAttributes(
-          java.lang.String key) {
-        if (key == null) { throw new java.lang.NullPointerException(); }
-        internalGetMutableAttributes().getMutableMap()
-            .remove(key);
-        return this;
-      }
-      /**
-       * Use alternate mutation accessors instead.
-       */
-      @java.lang.Deprecated
-      public java.util.Map<java.lang.String, java.lang.String>
-      getMutableAttributes() {
-        return internalGetMutableAttributes().getMutableMap();
-      }
-      /**
-       * <pre>
-       * Additional attributes of the identity.
-       * </pre>
-       *
-       * <code>map&lt;string, string&gt; attributes = 3;</code>
-       */
-      public Builder putAttributes(
-          java.lang.String key,
-          java.lang.String value) {
-        if (key == null) { throw new java.lang.NullPointerException(); }
-        if (value == null) { throw new java.lang.NullPointerException(); }
-        internalGetMutableAttributes().getMutableMap()
-            .put(key, value);
-        return this;
-      }
-      /**
-       * <pre>
-       * Additional attributes of the identity.
-       * </pre>
-       *
-       * <code>map&lt;string, string&gt; attributes = 3;</code>
-       */
-
-      public Builder putAllAttributes(
-          java.util.Map<java.lang.String, java.lang.String> values) {
-        internalGetMutableAttributes().getMutableMap()
-            .putAll(values);
-        return this;
-      }
-      public final Builder setUnknownFields(
-          final com.google.protobuf.UnknownFieldSet unknownFields) {
-        return super.setUnknownFieldsProto3(unknownFields);
-      }
-
-      public final Builder mergeUnknownFields(
-          final com.google.protobuf.UnknownFieldSet unknownFields) {
-        return super.mergeUnknownFields(unknownFields);
-      }
-
-
-      // @@protoc_insertion_point(builder_scope:grpc.gcp.Identity)
-    }
-
-    // @@protoc_insertion_point(class_scope:grpc.gcp.Identity)
-    private static final io.grpc.alts.internal.Handshaker.Identity DEFAULT_INSTANCE;
-    static {
-      DEFAULT_INSTANCE = new io.grpc.alts.internal.Handshaker.Identity();
-    }
-
-    public static io.grpc.alts.internal.Handshaker.Identity getDefaultInstance() {
-      return DEFAULT_INSTANCE;
-    }
-
-    private static final com.google.protobuf.Parser<Identity>
-        PARSER = new com.google.protobuf.AbstractParser<Identity>() {
-      public Identity parsePartialFrom(
-          com.google.protobuf.CodedInputStream input,
-          com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-          throws com.google.protobuf.InvalidProtocolBufferException {
-        return new Identity(input, extensionRegistry);
-      }
-    };
-
-    public static com.google.protobuf.Parser<Identity> parser() {
-      return PARSER;
-    }
-
-    @java.lang.Override
-    public com.google.protobuf.Parser<Identity> getParserForType() {
-      return PARSER;
-    }
-
-    public io.grpc.alts.internal.Handshaker.Identity getDefaultInstanceForType() {
-      return DEFAULT_INSTANCE;
-    }
-
-  }
-
-  public interface StartClientHandshakeReqOrBuilder extends
-      // @@protoc_insertion_point(interface_extends:grpc.gcp.StartClientHandshakeReq)
-      com.google.protobuf.MessageOrBuilder {
-
-    /**
-     * <pre>
-     * Handshake security protocol requested by the client.
-     * </pre>
-     *
-     * <code>.grpc.gcp.HandshakeProtocol handshake_security_protocol = 1;</code>
-     */
-    int getHandshakeSecurityProtocolValue();
-    /**
-     * <pre>
-     * Handshake security protocol requested by the client.
-     * </pre>
-     *
-     * <code>.grpc.gcp.HandshakeProtocol handshake_security_protocol = 1;</code>
-     */
-    io.grpc.alts.internal.Handshaker.HandshakeProtocol getHandshakeSecurityProtocol();
-
-    /**
-     * <pre>
-     * The application protocols supported by the client, e.g., "h2" (for http2),
-     * "grpc".
-     * </pre>
-     *
-     * <code>repeated string application_protocols = 2;</code>
-     */
-    java.util.List<java.lang.String>
-        getApplicationProtocolsList();
-    /**
-     * <pre>
-     * The application protocols supported by the client, e.g., "h2" (for http2),
-     * "grpc".
-     * </pre>
-     *
-     * <code>repeated string application_protocols = 2;</code>
-     */
-    int getApplicationProtocolsCount();
-    /**
-     * <pre>
-     * The application protocols supported by the client, e.g., "h2" (for http2),
-     * "grpc".
-     * </pre>
-     *
-     * <code>repeated string application_protocols = 2;</code>
-     */
-    java.lang.String getApplicationProtocols(int index);
-    /**
-     * <pre>
-     * The application protocols supported by the client, e.g., "h2" (for http2),
-     * "grpc".
-     * </pre>
-     *
-     * <code>repeated string application_protocols = 2;</code>
-     */
-    com.google.protobuf.ByteString
-        getApplicationProtocolsBytes(int index);
-
-    /**
-     * <pre>
-     * The record protocols supported by the client, e.g.,
-     * "ALTSRP_GCM_AES128".
-     * </pre>
-     *
-     * <code>repeated string record_protocols = 3;</code>
-     */
-    java.util.List<java.lang.String>
-        getRecordProtocolsList();
-    /**
-     * <pre>
-     * The record protocols supported by the client, e.g.,
-     * "ALTSRP_GCM_AES128".
-     * </pre>
-     *
-     * <code>repeated string record_protocols = 3;</code>
-     */
-    int getRecordProtocolsCount();
-    /**
-     * <pre>
-     * The record protocols supported by the client, e.g.,
-     * "ALTSRP_GCM_AES128".
-     * </pre>
-     *
-     * <code>repeated string record_protocols = 3;</code>
-     */
-    java.lang.String getRecordProtocols(int index);
-    /**
-     * <pre>
-     * The record protocols supported by the client, e.g.,
-     * "ALTSRP_GCM_AES128".
-     * </pre>
-     *
-     * <code>repeated string record_protocols = 3;</code>
-     */
-    com.google.protobuf.ByteString
-        getRecordProtocolsBytes(int index);
-
-    /**
-     * <pre>
-     * (Optional) Describes which server identities are acceptable by the client.
-     * If target identities are provided and none of them matches the peer
-     * identity of the server, handshake will fail.
-     * </pre>
-     *
-     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-     */
-    java.util.List<io.grpc.alts.internal.Handshaker.Identity> 
-        getTargetIdentitiesList();
-    /**
-     * <pre>
-     * (Optional) Describes which server identities are acceptable by the client.
-     * If target identities are provided and none of them matches the peer
-     * identity of the server, handshake will fail.
-     * </pre>
-     *
-     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-     */
-    io.grpc.alts.internal.Handshaker.Identity getTargetIdentities(int index);
-    /**
-     * <pre>
-     * (Optional) Describes which server identities are acceptable by the client.
-     * If target identities are provided and none of them matches the peer
-     * identity of the server, handshake will fail.
-     * </pre>
-     *
-     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-     */
-    int getTargetIdentitiesCount();
-    /**
-     * <pre>
-     * (Optional) Describes which server identities are acceptable by the client.
-     * If target identities are provided and none of them matches the peer
-     * identity of the server, handshake will fail.
-     * </pre>
-     *
-     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-     */
-    java.util.List<? extends io.grpc.alts.internal.Handshaker.IdentityOrBuilder> 
-        getTargetIdentitiesOrBuilderList();
-    /**
-     * <pre>
-     * (Optional) Describes which server identities are acceptable by the client.
-     * If target identities are provided and none of them matches the peer
-     * identity of the server, handshake will fail.
-     * </pre>
-     *
-     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-     */
-    io.grpc.alts.internal.Handshaker.IdentityOrBuilder getTargetIdentitiesOrBuilder(
-        int index);
-
-    /**
-     * <pre>
-     * (Optional) Application may specify a local identity. Otherwise, the
-     * handshaker chooses a default local identity.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Identity local_identity = 5;</code>
-     */
-    boolean hasLocalIdentity();
-    /**
-     * <pre>
-     * (Optional) Application may specify a local identity. Otherwise, the
-     * handshaker chooses a default local identity.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Identity local_identity = 5;</code>
-     */
-    io.grpc.alts.internal.Handshaker.Identity getLocalIdentity();
-    /**
-     * <pre>
-     * (Optional) Application may specify a local identity. Otherwise, the
-     * handshaker chooses a default local identity.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Identity local_identity = 5;</code>
-     */
-    io.grpc.alts.internal.Handshaker.IdentityOrBuilder getLocalIdentityOrBuilder();
-
-    /**
-     * <pre>
-     * (Optional) Local endpoint information of the connection to the server,
-     * such as local IP address, port number, and network protocol.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
-     */
-    boolean hasLocalEndpoint();
-    /**
-     * <pre>
-     * (Optional) Local endpoint information of the connection to the server,
-     * such as local IP address, port number, and network protocol.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
-     */
-    io.grpc.alts.internal.Handshaker.Endpoint getLocalEndpoint();
-    /**
-     * <pre>
-     * (Optional) Local endpoint information of the connection to the server,
-     * such as local IP address, port number, and network protocol.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
-     */
-    io.grpc.alts.internal.Handshaker.EndpointOrBuilder getLocalEndpointOrBuilder();
-
-    /**
-     * <pre>
-     * (Optional) Endpoint information of the remote server, such as IP address,
-     * port number, and network protocol.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
-     */
-    boolean hasRemoteEndpoint();
-    /**
-     * <pre>
-     * (Optional) Endpoint information of the remote server, such as IP address,
-     * port number, and network protocol.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
-     */
-    io.grpc.alts.internal.Handshaker.Endpoint getRemoteEndpoint();
-    /**
-     * <pre>
-     * (Optional) Endpoint information of the remote server, such as IP address,
-     * port number, and network protocol.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
-     */
-    io.grpc.alts.internal.Handshaker.EndpointOrBuilder getRemoteEndpointOrBuilder();
-
-    /**
-     * <pre>
-     * (Optional) If target name is provided, a secure naming check is performed
-     * to verify that the peer authenticated identity is indeed authorized to run
-     * the target name.
-     * </pre>
-     *
-     * <code>string target_name = 8;</code>
-     */
-    java.lang.String getTargetName();
-    /**
-     * <pre>
-     * (Optional) If target name is provided, a secure naming check is performed
-     * to verify that the peer authenticated identity is indeed authorized to run
-     * the target name.
-     * </pre>
-     *
-     * <code>string target_name = 8;</code>
-     */
-    com.google.protobuf.ByteString
-        getTargetNameBytes();
-
-    /**
-     * <pre>
-     * (Optional) RPC protocol versions supported by the client.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
-     */
-    boolean hasRpcVersions();
-    /**
-     * <pre>
-     * (Optional) RPC protocol versions supported by the client.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
-     */
-    io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions getRpcVersions();
-    /**
-     * <pre>
-     * (Optional) RPC protocol versions supported by the client.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
-     */
-    io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersionsOrBuilder getRpcVersionsOrBuilder();
-  }
-  /**
-   * Protobuf type {@code grpc.gcp.StartClientHandshakeReq}
-   */
-  public  static final class StartClientHandshakeReq extends
-      com.google.protobuf.GeneratedMessageV3 implements
-      // @@protoc_insertion_point(message_implements:grpc.gcp.StartClientHandshakeReq)
-      StartClientHandshakeReqOrBuilder {
-  private static final long serialVersionUID = 0L;
-    // Use StartClientHandshakeReq.newBuilder() to construct.
-    private StartClientHandshakeReq(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
-      super(builder);
-    }
-    private StartClientHandshakeReq() {
-      handshakeSecurityProtocol_ = 0;
-      applicationProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
-      recordProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
-      targetIdentities_ = java.util.Collections.emptyList();
-      targetName_ = "";
-    }
-
-    @java.lang.Override
-    public final com.google.protobuf.UnknownFieldSet
-    getUnknownFields() {
-      return this.unknownFields;
-    }
-    private StartClientHandshakeReq(
-        com.google.protobuf.CodedInputStream input,
-        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-        throws com.google.protobuf.InvalidProtocolBufferException {
-      this();
-      if (extensionRegistry == null) {
-        throw new java.lang.NullPointerException();
-      }
-      int mutable_bitField0_ = 0;
-      com.google.protobuf.UnknownFieldSet.Builder unknownFields =
-          com.google.protobuf.UnknownFieldSet.newBuilder();
-      try {
-        boolean done = false;
-        while (!done) {
-          int tag = input.readTag();
-          switch (tag) {
-            case 0:
-              done = true;
-              break;
-            default: {
-              if (!parseUnknownFieldProto3(
-                  input, unknownFields, extensionRegistry, tag)) {
-                done = true;
-              }
-              break;
-            }
-            case 8: {
-              int rawValue = input.readEnum();
-
-              handshakeSecurityProtocol_ = rawValue;
-              break;
-            }
-            case 18: {
-              java.lang.String s = input.readStringRequireUtf8();
-              if (!((mutable_bitField0_ & 0x00000002) == 0x00000002)) {
-                applicationProtocols_ = new com.google.protobuf.LazyStringArrayList();
-                mutable_bitField0_ |= 0x00000002;
-              }
-              applicationProtocols_.add(s);
-              break;
-            }
-            case 26: {
-              java.lang.String s = input.readStringRequireUtf8();
-              if (!((mutable_bitField0_ & 0x00000004) == 0x00000004)) {
-                recordProtocols_ = new com.google.protobuf.LazyStringArrayList();
-                mutable_bitField0_ |= 0x00000004;
-              }
-              recordProtocols_.add(s);
-              break;
-            }
-            case 34: {
-              if (!((mutable_bitField0_ & 0x00000008) == 0x00000008)) {
-                targetIdentities_ = new java.util.ArrayList<io.grpc.alts.internal.Handshaker.Identity>();
-                mutable_bitField0_ |= 0x00000008;
-              }
-              targetIdentities_.add(
-                  input.readMessage(io.grpc.alts.internal.Handshaker.Identity.parser(), extensionRegistry));
-              break;
-            }
-            case 42: {
-              io.grpc.alts.internal.Handshaker.Identity.Builder subBuilder = null;
-              if (localIdentity_ != null) {
-                subBuilder = localIdentity_.toBuilder();
-              }
-              localIdentity_ = input.readMessage(io.grpc.alts.internal.Handshaker.Identity.parser(), extensionRegistry);
-              if (subBuilder != null) {
-                subBuilder.mergeFrom(localIdentity_);
-                localIdentity_ = subBuilder.buildPartial();
-              }
-
-              break;
-            }
-            case 50: {
-              io.grpc.alts.internal.Handshaker.Endpoint.Builder subBuilder = null;
-              if (localEndpoint_ != null) {
-                subBuilder = localEndpoint_.toBuilder();
-              }
-              localEndpoint_ = input.readMessage(io.grpc.alts.internal.Handshaker.Endpoint.parser(), extensionRegistry);
-              if (subBuilder != null) {
-                subBuilder.mergeFrom(localEndpoint_);
-                localEndpoint_ = subBuilder.buildPartial();
-              }
-
-              break;
-            }
-            case 58: {
-              io.grpc.alts.internal.Handshaker.Endpoint.Builder subBuilder = null;
-              if (remoteEndpoint_ != null) {
-                subBuilder = remoteEndpoint_.toBuilder();
-              }
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-
-              targetName_ = s;
-              break;
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-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Builder subBuilder = null;
-              if (rpcVersions_ != null) {
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-              }
-              rpcVersions_ = input.readMessage(io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.parser(), extensionRegistry);
-              if (subBuilder != null) {
-                subBuilder.mergeFrom(rpcVersions_);
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-              }
-
-              break;
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-        }
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-        }
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-          targetIdentities_ = java.util.Collections.unmodifiableList(targetIdentities_);
-        }
-        this.unknownFields = unknownFields.build();
-        makeExtensionsImmutable();
-      }
-    }
-    public static final com.google.protobuf.Descriptors.Descriptor
-        getDescriptor() {
-      return io.grpc.alts.internal.Handshaker.internal_static_grpc_gcp_StartClientHandshakeReq_descriptor;
-    }
-
-    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
-        internalGetFieldAccessorTable() {
-      return io.grpc.alts.internal.Handshaker.internal_static_grpc_gcp_StartClientHandshakeReq_fieldAccessorTable
-          .ensureFieldAccessorsInitialized(
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-    }
-
-    private int bitField0_;
-    public static final int HANDSHAKE_SECURITY_PROTOCOL_FIELD_NUMBER = 1;
-    private int handshakeSecurityProtocol_;
-    /**
-     * <pre>
-     * Handshake security protocol requested by the client.
-     * </pre>
-     *
-     * <code>.grpc.gcp.HandshakeProtocol handshake_security_protocol = 1;</code>
-     */
-    public int getHandshakeSecurityProtocolValue() {
-      return handshakeSecurityProtocol_;
-    }
-    /**
-     * <pre>
-     * Handshake security protocol requested by the client.
-     * </pre>
-     *
-     * <code>.grpc.gcp.HandshakeProtocol handshake_security_protocol = 1;</code>
-     */
-    public io.grpc.alts.internal.Handshaker.HandshakeProtocol getHandshakeSecurityProtocol() {
-      io.grpc.alts.internal.Handshaker.HandshakeProtocol result = io.grpc.alts.internal.Handshaker.HandshakeProtocol.valueOf(handshakeSecurityProtocol_);
-      return result == null ? io.grpc.alts.internal.Handshaker.HandshakeProtocol.UNRECOGNIZED : result;
-    }
-
-    public static final int APPLICATION_PROTOCOLS_FIELD_NUMBER = 2;
-    private com.google.protobuf.LazyStringList applicationProtocols_;
-    /**
-     * <pre>
-     * The application protocols supported by the client, e.g., "h2" (for http2),
-     * "grpc".
-     * </pre>
-     *
-     * <code>repeated string application_protocols = 2;</code>
-     */
-    public com.google.protobuf.ProtocolStringList
-        getApplicationProtocolsList() {
-      return applicationProtocols_;
-    }
-    /**
-     * <pre>
-     * The application protocols supported by the client, e.g., "h2" (for http2),
-     * "grpc".
-     * </pre>
-     *
-     * <code>repeated string application_protocols = 2;</code>
-     */
-    public int getApplicationProtocolsCount() {
-      return applicationProtocols_.size();
-    }
-    /**
-     * <pre>
-     * The application protocols supported by the client, e.g., "h2" (for http2),
-     * "grpc".
-     * </pre>
-     *
-     * <code>repeated string application_protocols = 2;</code>
-     */
-    public java.lang.String getApplicationProtocols(int index) {
-      return applicationProtocols_.get(index);
-    }
-    /**
-     * <pre>
-     * The application protocols supported by the client, e.g., "h2" (for http2),
-     * "grpc".
-     * </pre>
-     *
-     * <code>repeated string application_protocols = 2;</code>
-     */
-    public com.google.protobuf.ByteString
-        getApplicationProtocolsBytes(int index) {
-      return applicationProtocols_.getByteString(index);
-    }
-
-    public static final int RECORD_PROTOCOLS_FIELD_NUMBER = 3;
-    private com.google.protobuf.LazyStringList recordProtocols_;
-    /**
-     * <pre>
-     * The record protocols supported by the client, e.g.,
-     * "ALTSRP_GCM_AES128".
-     * </pre>
-     *
-     * <code>repeated string record_protocols = 3;</code>
-     */
-    public com.google.protobuf.ProtocolStringList
-        getRecordProtocolsList() {
-      return recordProtocols_;
-    }
-    /**
-     * <pre>
-     * The record protocols supported by the client, e.g.,
-     * "ALTSRP_GCM_AES128".
-     * </pre>
-     *
-     * <code>repeated string record_protocols = 3;</code>
-     */
-    public int getRecordProtocolsCount() {
-      return recordProtocols_.size();
-    }
-    /**
-     * <pre>
-     * The record protocols supported by the client, e.g.,
-     * "ALTSRP_GCM_AES128".
-     * </pre>
-     *
-     * <code>repeated string record_protocols = 3;</code>
-     */
-    public java.lang.String getRecordProtocols(int index) {
-      return recordProtocols_.get(index);
-    }
-    /**
-     * <pre>
-     * The record protocols supported by the client, e.g.,
-     * "ALTSRP_GCM_AES128".
-     * </pre>
-     *
-     * <code>repeated string record_protocols = 3;</code>
-     */
-    public com.google.protobuf.ByteString
-        getRecordProtocolsBytes(int index) {
-      return recordProtocols_.getByteString(index);
-    }
-
-    public static final int TARGET_IDENTITIES_FIELD_NUMBER = 4;
-    private java.util.List<io.grpc.alts.internal.Handshaker.Identity> targetIdentities_;
-    /**
-     * <pre>
-     * (Optional) Describes which server identities are acceptable by the client.
-     * If target identities are provided and none of them matches the peer
-     * identity of the server, handshake will fail.
-     * </pre>
-     *
-     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-     */
-    public java.util.List<io.grpc.alts.internal.Handshaker.Identity> getTargetIdentitiesList() {
-      return targetIdentities_;
-    }
-    /**
-     * <pre>
-     * (Optional) Describes which server identities are acceptable by the client.
-     * If target identities are provided and none of them matches the peer
-     * identity of the server, handshake will fail.
-     * </pre>
-     *
-     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-     */
-    public java.util.List<? extends io.grpc.alts.internal.Handshaker.IdentityOrBuilder> 
-        getTargetIdentitiesOrBuilderList() {
-      return targetIdentities_;
-    }
-    /**
-     * <pre>
-     * (Optional) Describes which server identities are acceptable by the client.
-     * If target identities are provided and none of them matches the peer
-     * identity of the server, handshake will fail.
-     * </pre>
-     *
-     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-     */
-    public int getTargetIdentitiesCount() {
-      return targetIdentities_.size();
-    }
-    /**
-     * <pre>
-     * (Optional) Describes which server identities are acceptable by the client.
-     * If target identities are provided and none of them matches the peer
-     * identity of the server, handshake will fail.
-     * </pre>
-     *
-     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-     */
-    public io.grpc.alts.internal.Handshaker.Identity getTargetIdentities(int index) {
-      return targetIdentities_.get(index);
-    }
-    /**
-     * <pre>
-     * (Optional) Describes which server identities are acceptable by the client.
-     * If target identities are provided and none of them matches the peer
-     * identity of the server, handshake will fail.
-     * </pre>
-     *
-     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-     */
-    public io.grpc.alts.internal.Handshaker.IdentityOrBuilder getTargetIdentitiesOrBuilder(
-        int index) {
-      return targetIdentities_.get(index);
-    }
-
-    public static final int LOCAL_IDENTITY_FIELD_NUMBER = 5;
-    private io.grpc.alts.internal.Handshaker.Identity localIdentity_;
-    /**
-     * <pre>
-     * (Optional) Application may specify a local identity. Otherwise, the
-     * handshaker chooses a default local identity.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Identity local_identity = 5;</code>
-     */
-    public boolean hasLocalIdentity() {
-      return localIdentity_ != null;
-    }
-    /**
-     * <pre>
-     * (Optional) Application may specify a local identity. Otherwise, the
-     * handshaker chooses a default local identity.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Identity local_identity = 5;</code>
-     */
-    public io.grpc.alts.internal.Handshaker.Identity getLocalIdentity() {
-      return localIdentity_ == null ? io.grpc.alts.internal.Handshaker.Identity.getDefaultInstance() : localIdentity_;
-    }
-    /**
-     * <pre>
-     * (Optional) Application may specify a local identity. Otherwise, the
-     * handshaker chooses a default local identity.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Identity local_identity = 5;</code>
-     */
-    public io.grpc.alts.internal.Handshaker.IdentityOrBuilder getLocalIdentityOrBuilder() {
-      return getLocalIdentity();
-    }
-
-    public static final int LOCAL_ENDPOINT_FIELD_NUMBER = 6;
-    private io.grpc.alts.internal.Handshaker.Endpoint localEndpoint_;
-    /**
-     * <pre>
-     * (Optional) Local endpoint information of the connection to the server,
-     * such as local IP address, port number, and network protocol.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
-     */
-    public boolean hasLocalEndpoint() {
-      return localEndpoint_ != null;
-    }
-    /**
-     * <pre>
-     * (Optional) Local endpoint information of the connection to the server,
-     * such as local IP address, port number, and network protocol.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
-     */
-    public io.grpc.alts.internal.Handshaker.Endpoint getLocalEndpoint() {
-      return localEndpoint_ == null ? io.grpc.alts.internal.Handshaker.Endpoint.getDefaultInstance() : localEndpoint_;
-    }
-    /**
-     * <pre>
-     * (Optional) Local endpoint information of the connection to the server,
-     * such as local IP address, port number, and network protocol.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
-     */
-    public io.grpc.alts.internal.Handshaker.EndpointOrBuilder getLocalEndpointOrBuilder() {
-      return getLocalEndpoint();
-    }
-
-    public static final int REMOTE_ENDPOINT_FIELD_NUMBER = 7;
-    private io.grpc.alts.internal.Handshaker.Endpoint remoteEndpoint_;
-    /**
-     * <pre>
-     * (Optional) Endpoint information of the remote server, such as IP address,
-     * port number, and network protocol.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
-     */
-    public boolean hasRemoteEndpoint() {
-      return remoteEndpoint_ != null;
-    }
-    /**
-     * <pre>
-     * (Optional) Endpoint information of the remote server, such as IP address,
-     * port number, and network protocol.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
-     */
-    public io.grpc.alts.internal.Handshaker.Endpoint getRemoteEndpoint() {
-      return remoteEndpoint_ == null ? io.grpc.alts.internal.Handshaker.Endpoint.getDefaultInstance() : remoteEndpoint_;
-    }
-    /**
-     * <pre>
-     * (Optional) Endpoint information of the remote server, such as IP address,
-     * port number, and network protocol.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
-     */
-    public io.grpc.alts.internal.Handshaker.EndpointOrBuilder getRemoteEndpointOrBuilder() {
-      return getRemoteEndpoint();
-    }
-
-    public static final int TARGET_NAME_FIELD_NUMBER = 8;
-    private volatile java.lang.Object targetName_;
-    /**
-     * <pre>
-     * (Optional) If target name is provided, a secure naming check is performed
-     * to verify that the peer authenticated identity is indeed authorized to run
-     * the target name.
-     * </pre>
-     *
-     * <code>string target_name = 8;</code>
-     */
-    public java.lang.String getTargetName() {
-      java.lang.Object ref = targetName_;
-      if (ref instanceof java.lang.String) {
-        return (java.lang.String) ref;
-      } else {
-        com.google.protobuf.ByteString bs = 
-            (com.google.protobuf.ByteString) ref;
-        java.lang.String s = bs.toStringUtf8();
-        targetName_ = s;
-        return s;
-      }
-    }
-    /**
-     * <pre>
-     * (Optional) If target name is provided, a secure naming check is performed
-     * to verify that the peer authenticated identity is indeed authorized to run
-     * the target name.
-     * </pre>
-     *
-     * <code>string target_name = 8;</code>
-     */
-    public com.google.protobuf.ByteString
-        getTargetNameBytes() {
-      java.lang.Object ref = targetName_;
-      if (ref instanceof java.lang.String) {
-        com.google.protobuf.ByteString b = 
-            com.google.protobuf.ByteString.copyFromUtf8(
-                (java.lang.String) ref);
-        targetName_ = b;
-        return b;
-      } else {
-        return (com.google.protobuf.ByteString) ref;
-      }
-    }
-
-    public static final int RPC_VERSIONS_FIELD_NUMBER = 9;
-    private io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions rpcVersions_;
-    /**
-     * <pre>
-     * (Optional) RPC protocol versions supported by the client.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
-     */
-    public boolean hasRpcVersions() {
-      return rpcVersions_ != null;
-    }
-    /**
-     * <pre>
-     * (Optional) RPC protocol versions supported by the client.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
-     */
-    public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions getRpcVersions() {
-      return rpcVersions_ == null ? io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.getDefaultInstance() : rpcVersions_;
-    }
-    /**
-     * <pre>
-     * (Optional) RPC protocol versions supported by the client.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
-     */
-    public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersionsOrBuilder getRpcVersionsOrBuilder() {
-      return getRpcVersions();
-    }
-
-    private byte memoizedIsInitialized = -1;
-    public final boolean isInitialized() {
-      byte isInitialized = memoizedIsInitialized;
-      if (isInitialized == 1) return true;
-      if (isInitialized == 0) return false;
-
-      memoizedIsInitialized = 1;
-      return true;
-    }
-
-    public void writeTo(com.google.protobuf.CodedOutputStream output)
-                        throws java.io.IOException {
-      if (handshakeSecurityProtocol_ != io.grpc.alts.internal.Handshaker.HandshakeProtocol.HANDSHAKE_PROTOCOL_UNSPECIFIED.getNumber()) {
-        output.writeEnum(1, handshakeSecurityProtocol_);
-      }
-      for (int i = 0; i < applicationProtocols_.size(); i++) {
-        com.google.protobuf.GeneratedMessageV3.writeString(output, 2, applicationProtocols_.getRaw(i));
-      }
-      for (int i = 0; i < recordProtocols_.size(); i++) {
-        com.google.protobuf.GeneratedMessageV3.writeString(output, 3, recordProtocols_.getRaw(i));
-      }
-      for (int i = 0; i < targetIdentities_.size(); i++) {
-        output.writeMessage(4, targetIdentities_.get(i));
-      }
-      if (localIdentity_ != null) {
-        output.writeMessage(5, getLocalIdentity());
-      }
-      if (localEndpoint_ != null) {
-        output.writeMessage(6, getLocalEndpoint());
-      }
-      if (remoteEndpoint_ != null) {
-        output.writeMessage(7, getRemoteEndpoint());
-      }
-      if (!getTargetNameBytes().isEmpty()) {
-        com.google.protobuf.GeneratedMessageV3.writeString(output, 8, targetName_);
-      }
-      if (rpcVersions_ != null) {
-        output.writeMessage(9, getRpcVersions());
-      }
-      unknownFields.writeTo(output);
-    }
-
-    public int getSerializedSize() {
-      int size = memoizedSize;
-      if (size != -1) return size;
-
-      size = 0;
-      if (handshakeSecurityProtocol_ != io.grpc.alts.internal.Handshaker.HandshakeProtocol.HANDSHAKE_PROTOCOL_UNSPECIFIED.getNumber()) {
-        size += com.google.protobuf.CodedOutputStream
-          .computeEnumSize(1, handshakeSecurityProtocol_);
-      }
-      {
-        int dataSize = 0;
-        for (int i = 0; i < applicationProtocols_.size(); i++) {
-          dataSize += computeStringSizeNoTag(applicationProtocols_.getRaw(i));
-        }
-        size += dataSize;
-        size += 1 * getApplicationProtocolsList().size();
-      }
-      {
-        int dataSize = 0;
-        for (int i = 0; i < recordProtocols_.size(); i++) {
-          dataSize += computeStringSizeNoTag(recordProtocols_.getRaw(i));
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-        size += dataSize;
-        size += 1 * getRecordProtocolsList().size();
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-          .computeMessageSize(4, targetIdentities_.get(i));
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-      if (localIdentity_ != null) {
-        size += com.google.protobuf.CodedOutputStream
-          .computeMessageSize(5, getLocalIdentity());
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-      if (localEndpoint_ != null) {
-        size += com.google.protobuf.CodedOutputStream
-          .computeMessageSize(6, getLocalEndpoint());
-      }
-      if (remoteEndpoint_ != null) {
-        size += com.google.protobuf.CodedOutputStream
-          .computeMessageSize(7, getRemoteEndpoint());
-      }
-      if (!getTargetNameBytes().isEmpty()) {
-        size += com.google.protobuf.GeneratedMessageV3.computeStringSize(8, targetName_);
-      }
-      if (rpcVersions_ != null) {
-        size += com.google.protobuf.CodedOutputStream
-          .computeMessageSize(9, getRpcVersions());
-      }
-      size += unknownFields.getSerializedSize();
-      memoizedSize = size;
-      return size;
-    }
-
-    @java.lang.Override
-    public boolean equals(final java.lang.Object obj) {
-      if (obj == this) {
-       return true;
-      }
-      if (!(obj instanceof io.grpc.alts.internal.Handshaker.StartClientHandshakeReq)) {
-        return super.equals(obj);
-      }
-      io.grpc.alts.internal.Handshaker.StartClientHandshakeReq other = (io.grpc.alts.internal.Handshaker.StartClientHandshakeReq) obj;
-
-      boolean result = true;
-      result = result && handshakeSecurityProtocol_ == other.handshakeSecurityProtocol_;
-      result = result && getApplicationProtocolsList()
-          .equals(other.getApplicationProtocolsList());
-      result = result && getRecordProtocolsList()
-          .equals(other.getRecordProtocolsList());
-      result = result && getTargetIdentitiesList()
-          .equals(other.getTargetIdentitiesList());
-      result = result && (hasLocalIdentity() == other.hasLocalIdentity());
-      if (hasLocalIdentity()) {
-        result = result && getLocalIdentity()
-            .equals(other.getLocalIdentity());
-      }
-      result = result && (hasLocalEndpoint() == other.hasLocalEndpoint());
-      if (hasLocalEndpoint()) {
-        result = result && getLocalEndpoint()
-            .equals(other.getLocalEndpoint());
-      }
-      result = result && (hasRemoteEndpoint() == other.hasRemoteEndpoint());
-      if (hasRemoteEndpoint()) {
-        result = result && getRemoteEndpoint()
-            .equals(other.getRemoteEndpoint());
-      }
-      result = result && getTargetName()
-          .equals(other.getTargetName());
-      result = result && (hasRpcVersions() == other.hasRpcVersions());
-      if (hasRpcVersions()) {
-        result = result && getRpcVersions()
-            .equals(other.getRpcVersions());
-      }
-      result = result && unknownFields.equals(other.unknownFields);
-      return result;
-    }
-
-    @java.lang.Override
-    public int hashCode() {
-      if (memoizedHashCode != 0) {
-        return memoizedHashCode;
-      }
-      int hash = 41;
-      hash = (19 * hash) + getDescriptor().hashCode();
-      hash = (37 * hash) + HANDSHAKE_SECURITY_PROTOCOL_FIELD_NUMBER;
-      hash = (53 * hash) + handshakeSecurityProtocol_;
-      if (getApplicationProtocolsCount() > 0) {
-        hash = (37 * hash) + APPLICATION_PROTOCOLS_FIELD_NUMBER;
-        hash = (53 * hash) + getApplicationProtocolsList().hashCode();
-      }
-      if (getRecordProtocolsCount() > 0) {
-        hash = (37 * hash) + RECORD_PROTOCOLS_FIELD_NUMBER;
-        hash = (53 * hash) + getRecordProtocolsList().hashCode();
-      }
-      if (getTargetIdentitiesCount() > 0) {
-        hash = (37 * hash) + TARGET_IDENTITIES_FIELD_NUMBER;
-        hash = (53 * hash) + getTargetIdentitiesList().hashCode();
-      }
-      if (hasLocalIdentity()) {
-        hash = (37 * hash) + LOCAL_IDENTITY_FIELD_NUMBER;
-        hash = (53 * hash) + getLocalIdentity().hashCode();
-      }
-      if (hasLocalEndpoint()) {
-        hash = (37 * hash) + LOCAL_ENDPOINT_FIELD_NUMBER;
-        hash = (53 * hash) + getLocalEndpoint().hashCode();
-      }
-      if (hasRemoteEndpoint()) {
-        hash = (37 * hash) + REMOTE_ENDPOINT_FIELD_NUMBER;
-        hash = (53 * hash) + getRemoteEndpoint().hashCode();
-      }
-      hash = (37 * hash) + TARGET_NAME_FIELD_NUMBER;
-      hash = (53 * hash) + getTargetName().hashCode();
-      if (hasRpcVersions()) {
-        hash = (37 * hash) + RPC_VERSIONS_FIELD_NUMBER;
-        hash = (53 * hash) + getRpcVersions().hashCode();
-      }
-      hash = (29 * hash) + unknownFields.hashCode();
-      memoizedHashCode = hash;
-      return hash;
-    }
-
-    public static io.grpc.alts.internal.Handshaker.StartClientHandshakeReq parseFrom(
-        java.nio.ByteBuffer data)
-        throws com.google.protobuf.InvalidProtocolBufferException {
-      return PARSER.parseFrom(data);
-    }
-    public static io.grpc.alts.internal.Handshaker.StartClientHandshakeReq parseFrom(
-        java.nio.ByteBuffer data,
-        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-        throws com.google.protobuf.InvalidProtocolBufferException {
-      return PARSER.parseFrom(data, extensionRegistry);
-    }
-    public static io.grpc.alts.internal.Handshaker.StartClientHandshakeReq parseFrom(
-        com.google.protobuf.ByteString data)
-        throws com.google.protobuf.InvalidProtocolBufferException {
-      return PARSER.parseFrom(data);
-    }
-    public static io.grpc.alts.internal.Handshaker.StartClientHandshakeReq parseFrom(
-        com.google.protobuf.ByteString data,
-        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-        throws com.google.protobuf.InvalidProtocolBufferException {
-      return PARSER.parseFrom(data, extensionRegistry);
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-      }
-
-      private java.util.List<io.grpc.alts.internal.Handshaker.Identity> targetIdentities_ =
-        java.util.Collections.emptyList();
-      private void ensureTargetIdentitiesIsMutable() {
-        if (!((bitField0_ & 0x00000008) == 0x00000008)) {
-          targetIdentities_ = new java.util.ArrayList<io.grpc.alts.internal.Handshaker.Identity>(targetIdentities_);
-          bitField0_ |= 0x00000008;
-         }
-      }
-
-      private com.google.protobuf.RepeatedFieldBuilderV3<
-          io.grpc.alts.internal.Handshaker.Identity, io.grpc.alts.internal.Handshaker.Identity.Builder, io.grpc.alts.internal.Handshaker.IdentityOrBuilder> targetIdentitiesBuilder_;
-
-      /**
-       * <pre>
-       * (Optional) Describes which server identities are acceptable by the client.
-       * If target identities are provided and none of them matches the peer
-       * identity of the server, handshake will fail.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-       */
-      public java.util.List<io.grpc.alts.internal.Handshaker.Identity> getTargetIdentitiesList() {
-        if (targetIdentitiesBuilder_ == null) {
-          return java.util.Collections.unmodifiableList(targetIdentities_);
-        } else {
-          return targetIdentitiesBuilder_.getMessageList();
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) Describes which server identities are acceptable by the client.
-       * If target identities are provided and none of them matches the peer
-       * identity of the server, handshake will fail.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-       */
-      public int getTargetIdentitiesCount() {
-        if (targetIdentitiesBuilder_ == null) {
-          return targetIdentities_.size();
-        } else {
-          return targetIdentitiesBuilder_.getCount();
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) Describes which server identities are acceptable by the client.
-       * If target identities are provided and none of them matches the peer
-       * identity of the server, handshake will fail.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.Identity getTargetIdentities(int index) {
-        if (targetIdentitiesBuilder_ == null) {
-          return targetIdentities_.get(index);
-        } else {
-          return targetIdentitiesBuilder_.getMessage(index);
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) Describes which server identities are acceptable by the client.
-       * If target identities are provided and none of them matches the peer
-       * identity of the server, handshake will fail.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-       */
-      public Builder setTargetIdentities(
-          int index, io.grpc.alts.internal.Handshaker.Identity value) {
-        if (targetIdentitiesBuilder_ == null) {
-          if (value == null) {
-            throw new NullPointerException();
-          }
-          ensureTargetIdentitiesIsMutable();
-          targetIdentities_.set(index, value);
-          onChanged();
-        } else {
-          targetIdentitiesBuilder_.setMessage(index, value);
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Describes which server identities are acceptable by the client.
-       * If target identities are provided and none of them matches the peer
-       * identity of the server, handshake will fail.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-       */
-      public Builder setTargetIdentities(
-          int index, io.grpc.alts.internal.Handshaker.Identity.Builder builderForValue) {
-        if (targetIdentitiesBuilder_ == null) {
-          ensureTargetIdentitiesIsMutable();
-          targetIdentities_.set(index, builderForValue.build());
-          onChanged();
-        } else {
-          targetIdentitiesBuilder_.setMessage(index, builderForValue.build());
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Describes which server identities are acceptable by the client.
-       * If target identities are provided and none of them matches the peer
-       * identity of the server, handshake will fail.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-       */
-      public Builder addTargetIdentities(io.grpc.alts.internal.Handshaker.Identity value) {
-        if (targetIdentitiesBuilder_ == null) {
-          if (value == null) {
-            throw new NullPointerException();
-          }
-          ensureTargetIdentitiesIsMutable();
-          targetIdentities_.add(value);
-          onChanged();
-        } else {
-          targetIdentitiesBuilder_.addMessage(value);
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Describes which server identities are acceptable by the client.
-       * If target identities are provided and none of them matches the peer
-       * identity of the server, handshake will fail.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-       */
-      public Builder addTargetIdentities(
-          int index, io.grpc.alts.internal.Handshaker.Identity value) {
-        if (targetIdentitiesBuilder_ == null) {
-          if (value == null) {
-            throw new NullPointerException();
-          }
-          ensureTargetIdentitiesIsMutable();
-          targetIdentities_.add(index, value);
-          onChanged();
-        } else {
-          targetIdentitiesBuilder_.addMessage(index, value);
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Describes which server identities are acceptable by the client.
-       * If target identities are provided and none of them matches the peer
-       * identity of the server, handshake will fail.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-       */
-      public Builder addTargetIdentities(
-          io.grpc.alts.internal.Handshaker.Identity.Builder builderForValue) {
-        if (targetIdentitiesBuilder_ == null) {
-          ensureTargetIdentitiesIsMutable();
-          targetIdentities_.add(builderForValue.build());
-          onChanged();
-        } else {
-          targetIdentitiesBuilder_.addMessage(builderForValue.build());
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Describes which server identities are acceptable by the client.
-       * If target identities are provided and none of them matches the peer
-       * identity of the server, handshake will fail.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-       */
-      public Builder addTargetIdentities(
-          int index, io.grpc.alts.internal.Handshaker.Identity.Builder builderForValue) {
-        if (targetIdentitiesBuilder_ == null) {
-          ensureTargetIdentitiesIsMutable();
-          targetIdentities_.add(index, builderForValue.build());
-          onChanged();
-        } else {
-          targetIdentitiesBuilder_.addMessage(index, builderForValue.build());
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Describes which server identities are acceptable by the client.
-       * If target identities are provided and none of them matches the peer
-       * identity of the server, handshake will fail.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-       */
-      public Builder addAllTargetIdentities(
-          java.lang.Iterable<? extends io.grpc.alts.internal.Handshaker.Identity> values) {
-        if (targetIdentitiesBuilder_ == null) {
-          ensureTargetIdentitiesIsMutable();
-          com.google.protobuf.AbstractMessageLite.Builder.addAll(
-              values, targetIdentities_);
-          onChanged();
-        } else {
-          targetIdentitiesBuilder_.addAllMessages(values);
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Describes which server identities are acceptable by the client.
-       * If target identities are provided and none of them matches the peer
-       * identity of the server, handshake will fail.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-       */
-      public Builder clearTargetIdentities() {
-        if (targetIdentitiesBuilder_ == null) {
-          targetIdentities_ = java.util.Collections.emptyList();
-          bitField0_ = (bitField0_ & ~0x00000008);
-          onChanged();
-        } else {
-          targetIdentitiesBuilder_.clear();
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Describes which server identities are acceptable by the client.
-       * If target identities are provided and none of them matches the peer
-       * identity of the server, handshake will fail.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-       */
-      public Builder removeTargetIdentities(int index) {
-        if (targetIdentitiesBuilder_ == null) {
-          ensureTargetIdentitiesIsMutable();
-          targetIdentities_.remove(index);
-          onChanged();
-        } else {
-          targetIdentitiesBuilder_.remove(index);
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Describes which server identities are acceptable by the client.
-       * If target identities are provided and none of them matches the peer
-       * identity of the server, handshake will fail.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.Identity.Builder getTargetIdentitiesBuilder(
-          int index) {
-        return getTargetIdentitiesFieldBuilder().getBuilder(index);
-      }
-      /**
-       * <pre>
-       * (Optional) Describes which server identities are acceptable by the client.
-       * If target identities are provided and none of them matches the peer
-       * identity of the server, handshake will fail.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.IdentityOrBuilder getTargetIdentitiesOrBuilder(
-          int index) {
-        if (targetIdentitiesBuilder_ == null) {
-          return targetIdentities_.get(index);  } else {
-          return targetIdentitiesBuilder_.getMessageOrBuilder(index);
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) Describes which server identities are acceptable by the client.
-       * If target identities are provided and none of them matches the peer
-       * identity of the server, handshake will fail.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-       */
-      public java.util.List<? extends io.grpc.alts.internal.Handshaker.IdentityOrBuilder> 
-           getTargetIdentitiesOrBuilderList() {
-        if (targetIdentitiesBuilder_ != null) {
-          return targetIdentitiesBuilder_.getMessageOrBuilderList();
-        } else {
-          return java.util.Collections.unmodifiableList(targetIdentities_);
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) Describes which server identities are acceptable by the client.
-       * If target identities are provided and none of them matches the peer
-       * identity of the server, handshake will fail.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.Identity.Builder addTargetIdentitiesBuilder() {
-        return getTargetIdentitiesFieldBuilder().addBuilder(
-            io.grpc.alts.internal.Handshaker.Identity.getDefaultInstance());
-      }
-      /**
-       * <pre>
-       * (Optional) Describes which server identities are acceptable by the client.
-       * If target identities are provided and none of them matches the peer
-       * identity of the server, handshake will fail.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.Identity.Builder addTargetIdentitiesBuilder(
-          int index) {
-        return getTargetIdentitiesFieldBuilder().addBuilder(
-            index, io.grpc.alts.internal.Handshaker.Identity.getDefaultInstance());
-      }
-      /**
-       * <pre>
-       * (Optional) Describes which server identities are acceptable by the client.
-       * If target identities are provided and none of them matches the peer
-       * identity of the server, handshake will fail.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
-       */
-      public java.util.List<io.grpc.alts.internal.Handshaker.Identity.Builder> 
-           getTargetIdentitiesBuilderList() {
-        return getTargetIdentitiesFieldBuilder().getBuilderList();
-      }
-      private com.google.protobuf.RepeatedFieldBuilderV3<
-          io.grpc.alts.internal.Handshaker.Identity, io.grpc.alts.internal.Handshaker.Identity.Builder, io.grpc.alts.internal.Handshaker.IdentityOrBuilder> 
-          getTargetIdentitiesFieldBuilder() {
-        if (targetIdentitiesBuilder_ == null) {
-          targetIdentitiesBuilder_ = new com.google.protobuf.RepeatedFieldBuilderV3<
-              io.grpc.alts.internal.Handshaker.Identity, io.grpc.alts.internal.Handshaker.Identity.Builder, io.grpc.alts.internal.Handshaker.IdentityOrBuilder>(
-                  targetIdentities_,
-                  ((bitField0_ & 0x00000008) == 0x00000008),
-                  getParentForChildren(),
-                  isClean());
-          targetIdentities_ = null;
-        }
-        return targetIdentitiesBuilder_;
-      }
-
-      private io.grpc.alts.internal.Handshaker.Identity localIdentity_ = null;
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.Handshaker.Identity, io.grpc.alts.internal.Handshaker.Identity.Builder, io.grpc.alts.internal.Handshaker.IdentityOrBuilder> localIdentityBuilder_;
-      /**
-       * <pre>
-       * (Optional) Application may specify a local identity. Otherwise, the
-       * handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity local_identity = 5;</code>
-       */
-      public boolean hasLocalIdentity() {
-        return localIdentityBuilder_ != null || localIdentity_ != null;
-      }
-      /**
-       * <pre>
-       * (Optional) Application may specify a local identity. Otherwise, the
-       * handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity local_identity = 5;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.Identity getLocalIdentity() {
-        if (localIdentityBuilder_ == null) {
-          return localIdentity_ == null ? io.grpc.alts.internal.Handshaker.Identity.getDefaultInstance() : localIdentity_;
-        } else {
-          return localIdentityBuilder_.getMessage();
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) Application may specify a local identity. Otherwise, the
-       * handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity local_identity = 5;</code>
-       */
-      public Builder setLocalIdentity(io.grpc.alts.internal.Handshaker.Identity value) {
-        if (localIdentityBuilder_ == null) {
-          if (value == null) {
-            throw new NullPointerException();
-          }
-          localIdentity_ = value;
-          onChanged();
-        } else {
-          localIdentityBuilder_.setMessage(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Application may specify a local identity. Otherwise, the
-       * handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity local_identity = 5;</code>
-       */
-      public Builder setLocalIdentity(
-          io.grpc.alts.internal.Handshaker.Identity.Builder builderForValue) {
-        if (localIdentityBuilder_ == null) {
-          localIdentity_ = builderForValue.build();
-          onChanged();
-        } else {
-          localIdentityBuilder_.setMessage(builderForValue.build());
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Application may specify a local identity. Otherwise, the
-       * handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity local_identity = 5;</code>
-       */
-      public Builder mergeLocalIdentity(io.grpc.alts.internal.Handshaker.Identity value) {
-        if (localIdentityBuilder_ == null) {
-          if (localIdentity_ != null) {
-            localIdentity_ =
-              io.grpc.alts.internal.Handshaker.Identity.newBuilder(localIdentity_).mergeFrom(value).buildPartial();
-          } else {
-            localIdentity_ = value;
-          }
-          onChanged();
-        } else {
-          localIdentityBuilder_.mergeFrom(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Application may specify a local identity. Otherwise, the
-       * handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity local_identity = 5;</code>
-       */
-      public Builder clearLocalIdentity() {
-        if (localIdentityBuilder_ == null) {
-          localIdentity_ = null;
-          onChanged();
-        } else {
-          localIdentity_ = null;
-          localIdentityBuilder_ = null;
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Application may specify a local identity. Otherwise, the
-       * handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity local_identity = 5;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.Identity.Builder getLocalIdentityBuilder() {
-        
-        onChanged();
-        return getLocalIdentityFieldBuilder().getBuilder();
-      }
-      /**
-       * <pre>
-       * (Optional) Application may specify a local identity. Otherwise, the
-       * handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity local_identity = 5;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.IdentityOrBuilder getLocalIdentityOrBuilder() {
-        if (localIdentityBuilder_ != null) {
-          return localIdentityBuilder_.getMessageOrBuilder();
-        } else {
-          return localIdentity_ == null ?
-              io.grpc.alts.internal.Handshaker.Identity.getDefaultInstance() : localIdentity_;
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) Application may specify a local identity. Otherwise, the
-       * handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity local_identity = 5;</code>
-       */
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.Handshaker.Identity, io.grpc.alts.internal.Handshaker.Identity.Builder, io.grpc.alts.internal.Handshaker.IdentityOrBuilder> 
-          getLocalIdentityFieldBuilder() {
-        if (localIdentityBuilder_ == null) {
-          localIdentityBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
-              io.grpc.alts.internal.Handshaker.Identity, io.grpc.alts.internal.Handshaker.Identity.Builder, io.grpc.alts.internal.Handshaker.IdentityOrBuilder>(
-                  getLocalIdentity(),
-                  getParentForChildren(),
-                  isClean());
-          localIdentity_ = null;
-        }
-        return localIdentityBuilder_;
-      }
-
-      private io.grpc.alts.internal.Handshaker.Endpoint localEndpoint_ = null;
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.Handshaker.Endpoint, io.grpc.alts.internal.Handshaker.Endpoint.Builder, io.grpc.alts.internal.Handshaker.EndpointOrBuilder> localEndpointBuilder_;
-      /**
-       * <pre>
-       * (Optional) Local endpoint information of the connection to the server,
-       * such as local IP address, port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
-       */
-      public boolean hasLocalEndpoint() {
-        return localEndpointBuilder_ != null || localEndpoint_ != null;
-      }
-      /**
-       * <pre>
-       * (Optional) Local endpoint information of the connection to the server,
-       * such as local IP address, port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.Endpoint getLocalEndpoint() {
-        if (localEndpointBuilder_ == null) {
-          return localEndpoint_ == null ? io.grpc.alts.internal.Handshaker.Endpoint.getDefaultInstance() : localEndpoint_;
-        } else {
-          return localEndpointBuilder_.getMessage();
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) Local endpoint information of the connection to the server,
-       * such as local IP address, port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
-       */
-      public Builder setLocalEndpoint(io.grpc.alts.internal.Handshaker.Endpoint value) {
-        if (localEndpointBuilder_ == null) {
-          if (value == null) {
-            throw new NullPointerException();
-          }
-          localEndpoint_ = value;
-          onChanged();
-        } else {
-          localEndpointBuilder_.setMessage(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Local endpoint information of the connection to the server,
-       * such as local IP address, port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
-       */
-      public Builder setLocalEndpoint(
-          io.grpc.alts.internal.Handshaker.Endpoint.Builder builderForValue) {
-        if (localEndpointBuilder_ == null) {
-          localEndpoint_ = builderForValue.build();
-          onChanged();
-        } else {
-          localEndpointBuilder_.setMessage(builderForValue.build());
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Local endpoint information of the connection to the server,
-       * such as local IP address, port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
-       */
-      public Builder mergeLocalEndpoint(io.grpc.alts.internal.Handshaker.Endpoint value) {
-        if (localEndpointBuilder_ == null) {
-          if (localEndpoint_ != null) {
-            localEndpoint_ =
-              io.grpc.alts.internal.Handshaker.Endpoint.newBuilder(localEndpoint_).mergeFrom(value).buildPartial();
-          } else {
-            localEndpoint_ = value;
-          }
-          onChanged();
-        } else {
-          localEndpointBuilder_.mergeFrom(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Local endpoint information of the connection to the server,
-       * such as local IP address, port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
-       */
-      public Builder clearLocalEndpoint() {
-        if (localEndpointBuilder_ == null) {
-          localEndpoint_ = null;
-          onChanged();
-        } else {
-          localEndpoint_ = null;
-          localEndpointBuilder_ = null;
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Local endpoint information of the connection to the server,
-       * such as local IP address, port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.Endpoint.Builder getLocalEndpointBuilder() {
-        
-        onChanged();
-        return getLocalEndpointFieldBuilder().getBuilder();
-      }
-      /**
-       * <pre>
-       * (Optional) Local endpoint information of the connection to the server,
-       * such as local IP address, port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.EndpointOrBuilder getLocalEndpointOrBuilder() {
-        if (localEndpointBuilder_ != null) {
-          return localEndpointBuilder_.getMessageOrBuilder();
-        } else {
-          return localEndpoint_ == null ?
-              io.grpc.alts.internal.Handshaker.Endpoint.getDefaultInstance() : localEndpoint_;
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) Local endpoint information of the connection to the server,
-       * such as local IP address, port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
-       */
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.Handshaker.Endpoint, io.grpc.alts.internal.Handshaker.Endpoint.Builder, io.grpc.alts.internal.Handshaker.EndpointOrBuilder> 
-          getLocalEndpointFieldBuilder() {
-        if (localEndpointBuilder_ == null) {
-          localEndpointBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
-              io.grpc.alts.internal.Handshaker.Endpoint, io.grpc.alts.internal.Handshaker.Endpoint.Builder, io.grpc.alts.internal.Handshaker.EndpointOrBuilder>(
-                  getLocalEndpoint(),
-                  getParentForChildren(),
-                  isClean());
-          localEndpoint_ = null;
-        }
-        return localEndpointBuilder_;
-      }
-
-      private io.grpc.alts.internal.Handshaker.Endpoint remoteEndpoint_ = null;
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.Handshaker.Endpoint, io.grpc.alts.internal.Handshaker.Endpoint.Builder, io.grpc.alts.internal.Handshaker.EndpointOrBuilder> remoteEndpointBuilder_;
-      /**
-       * <pre>
-       * (Optional) Endpoint information of the remote server, such as IP address,
-       * port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
-       */
-      public boolean hasRemoteEndpoint() {
-        return remoteEndpointBuilder_ != null || remoteEndpoint_ != null;
-      }
-      /**
-       * <pre>
-       * (Optional) Endpoint information of the remote server, such as IP address,
-       * port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.Endpoint getRemoteEndpoint() {
-        if (remoteEndpointBuilder_ == null) {
-          return remoteEndpoint_ == null ? io.grpc.alts.internal.Handshaker.Endpoint.getDefaultInstance() : remoteEndpoint_;
-        } else {
-          return remoteEndpointBuilder_.getMessage();
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) Endpoint information of the remote server, such as IP address,
-       * port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
-       */
-      public Builder setRemoteEndpoint(io.grpc.alts.internal.Handshaker.Endpoint value) {
-        if (remoteEndpointBuilder_ == null) {
-          if (value == null) {
-            throw new NullPointerException();
-          }
-          remoteEndpoint_ = value;
-          onChanged();
-        } else {
-          remoteEndpointBuilder_.setMessage(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Endpoint information of the remote server, such as IP address,
-       * port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
-       */
-      public Builder setRemoteEndpoint(
-          io.grpc.alts.internal.Handshaker.Endpoint.Builder builderForValue) {
-        if (remoteEndpointBuilder_ == null) {
-          remoteEndpoint_ = builderForValue.build();
-          onChanged();
-        } else {
-          remoteEndpointBuilder_.setMessage(builderForValue.build());
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Endpoint information of the remote server, such as IP address,
-       * port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
-       */
-      public Builder mergeRemoteEndpoint(io.grpc.alts.internal.Handshaker.Endpoint value) {
-        if (remoteEndpointBuilder_ == null) {
-          if (remoteEndpoint_ != null) {
-            remoteEndpoint_ =
-              io.grpc.alts.internal.Handshaker.Endpoint.newBuilder(remoteEndpoint_).mergeFrom(value).buildPartial();
-          } else {
-            remoteEndpoint_ = value;
-          }
-          onChanged();
-        } else {
-          remoteEndpointBuilder_.mergeFrom(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Endpoint information of the remote server, such as IP address,
-       * port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
-       */
-      public Builder clearRemoteEndpoint() {
-        if (remoteEndpointBuilder_ == null) {
-          remoteEndpoint_ = null;
-          onChanged();
-        } else {
-          remoteEndpoint_ = null;
-          remoteEndpointBuilder_ = null;
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Endpoint information of the remote server, such as IP address,
-       * port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.Endpoint.Builder getRemoteEndpointBuilder() {
-        
-        onChanged();
-        return getRemoteEndpointFieldBuilder().getBuilder();
-      }
-      /**
-       * <pre>
-       * (Optional) Endpoint information of the remote server, such as IP address,
-       * port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.EndpointOrBuilder getRemoteEndpointOrBuilder() {
-        if (remoteEndpointBuilder_ != null) {
-          return remoteEndpointBuilder_.getMessageOrBuilder();
-        } else {
-          return remoteEndpoint_ == null ?
-              io.grpc.alts.internal.Handshaker.Endpoint.getDefaultInstance() : remoteEndpoint_;
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) Endpoint information of the remote server, such as IP address,
-       * port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
-       */
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.Handshaker.Endpoint, io.grpc.alts.internal.Handshaker.Endpoint.Builder, io.grpc.alts.internal.Handshaker.EndpointOrBuilder> 
-          getRemoteEndpointFieldBuilder() {
-        if (remoteEndpointBuilder_ == null) {
-          remoteEndpointBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
-              io.grpc.alts.internal.Handshaker.Endpoint, io.grpc.alts.internal.Handshaker.Endpoint.Builder, io.grpc.alts.internal.Handshaker.EndpointOrBuilder>(
-                  getRemoteEndpoint(),
-                  getParentForChildren(),
-                  isClean());
-          remoteEndpoint_ = null;
-        }
-        return remoteEndpointBuilder_;
-      }
-
-      private java.lang.Object targetName_ = "";
-      /**
-       * <pre>
-       * (Optional) If target name is provided, a secure naming check is performed
-       * to verify that the peer authenticated identity is indeed authorized to run
-       * the target name.
-       * </pre>
-       *
-       * <code>string target_name = 8;</code>
-       */
-      public java.lang.String getTargetName() {
-        java.lang.Object ref = targetName_;
-        if (!(ref instanceof java.lang.String)) {
-          com.google.protobuf.ByteString bs =
-              (com.google.protobuf.ByteString) ref;
-          java.lang.String s = bs.toStringUtf8();
-          targetName_ = s;
-          return s;
-        } else {
-          return (java.lang.String) ref;
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) If target name is provided, a secure naming check is performed
-       * to verify that the peer authenticated identity is indeed authorized to run
-       * the target name.
-       * </pre>
-       *
-       * <code>string target_name = 8;</code>
-       */
-      public com.google.protobuf.ByteString
-          getTargetNameBytes() {
-        java.lang.Object ref = targetName_;
-        if (ref instanceof String) {
-          com.google.protobuf.ByteString b = 
-              com.google.protobuf.ByteString.copyFromUtf8(
-                  (java.lang.String) ref);
-          targetName_ = b;
-          return b;
-        } else {
-          return (com.google.protobuf.ByteString) ref;
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) If target name is provided, a secure naming check is performed
-       * to verify that the peer authenticated identity is indeed authorized to run
-       * the target name.
-       * </pre>
-       *
-       * <code>string target_name = 8;</code>
-       */
-      public Builder setTargetName(
-          java.lang.String value) {
-        if (value == null) {
-    throw new NullPointerException();
-  }
-  
-        targetName_ = value;
-        onChanged();
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) If target name is provided, a secure naming check is performed
-       * to verify that the peer authenticated identity is indeed authorized to run
-       * the target name.
-       * </pre>
-       *
-       * <code>string target_name = 8;</code>
-       */
-      public Builder clearTargetName() {
-        
-        targetName_ = getDefaultInstance().getTargetName();
-        onChanged();
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) If target name is provided, a secure naming check is performed
-       * to verify that the peer authenticated identity is indeed authorized to run
-       * the target name.
-       * </pre>
-       *
-       * <code>string target_name = 8;</code>
-       */
-      public Builder setTargetNameBytes(
-          com.google.protobuf.ByteString value) {
-        if (value == null) {
-    throw new NullPointerException();
-  }
-  checkByteStringIsUtf8(value);
-        
-        targetName_ = value;
-        onChanged();
-        return this;
-      }
-
-      private io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions rpcVersions_ = null;
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Builder, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersionsOrBuilder> rpcVersionsBuilder_;
-      /**
-       * <pre>
-       * (Optional) RPC protocol versions supported by the client.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
-       */
-      public boolean hasRpcVersions() {
-        return rpcVersionsBuilder_ != null || rpcVersions_ != null;
-      }
-      /**
-       * <pre>
-       * (Optional) RPC protocol versions supported by the client.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
-       */
-      public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions getRpcVersions() {
-        if (rpcVersionsBuilder_ == null) {
-          return rpcVersions_ == null ? io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.getDefaultInstance() : rpcVersions_;
-        } else {
-          return rpcVersionsBuilder_.getMessage();
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) RPC protocol versions supported by the client.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
-       */
-      public Builder setRpcVersions(io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions value) {
-        if (rpcVersionsBuilder_ == null) {
-          if (value == null) {
-            throw new NullPointerException();
-          }
-          rpcVersions_ = value;
-          onChanged();
-        } else {
-          rpcVersionsBuilder_.setMessage(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) RPC protocol versions supported by the client.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
-       */
-      public Builder setRpcVersions(
-          io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Builder builderForValue) {
-        if (rpcVersionsBuilder_ == null) {
-          rpcVersions_ = builderForValue.build();
-          onChanged();
-        } else {
-          rpcVersionsBuilder_.setMessage(builderForValue.build());
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) RPC protocol versions supported by the client.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
-       */
-      public Builder mergeRpcVersions(io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions value) {
-        if (rpcVersionsBuilder_ == null) {
-          if (rpcVersions_ != null) {
-            rpcVersions_ =
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.newBuilder(rpcVersions_).mergeFrom(value).buildPartial();
-          } else {
-            rpcVersions_ = value;
-          }
-          onChanged();
-        } else {
-          rpcVersionsBuilder_.mergeFrom(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) RPC protocol versions supported by the client.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
-       */
-      public Builder clearRpcVersions() {
-        if (rpcVersionsBuilder_ == null) {
-          rpcVersions_ = null;
-          onChanged();
-        } else {
-          rpcVersions_ = null;
-          rpcVersionsBuilder_ = null;
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) RPC protocol versions supported by the client.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
-       */
-      public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Builder getRpcVersionsBuilder() {
-        
-        onChanged();
-        return getRpcVersionsFieldBuilder().getBuilder();
-      }
-      /**
-       * <pre>
-       * (Optional) RPC protocol versions supported by the client.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
-       */
-      public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersionsOrBuilder getRpcVersionsOrBuilder() {
-        if (rpcVersionsBuilder_ != null) {
-          return rpcVersionsBuilder_.getMessageOrBuilder();
-        } else {
-          return rpcVersions_ == null ?
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.getDefaultInstance() : rpcVersions_;
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) RPC protocol versions supported by the client.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
-       */
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Builder, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersionsOrBuilder> 
-          getRpcVersionsFieldBuilder() {
-        if (rpcVersionsBuilder_ == null) {
-          rpcVersionsBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Builder, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersionsOrBuilder>(
-                  getRpcVersions(),
-                  getParentForChildren(),
-                  isClean());
-          rpcVersions_ = null;
-        }
-        return rpcVersionsBuilder_;
-      }
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-        return super.setUnknownFieldsProto3(unknownFields);
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-      public final Builder mergeUnknownFields(
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-        return super.mergeUnknownFields(unknownFields);
-      }
-
-
-      // @@protoc_insertion_point(builder_scope:grpc.gcp.StartClientHandshakeReq)
-    }
-
-    // @@protoc_insertion_point(class_scope:grpc.gcp.StartClientHandshakeReq)
-    private static final io.grpc.alts.internal.Handshaker.StartClientHandshakeReq DEFAULT_INSTANCE;
-    static {
-      DEFAULT_INSTANCE = new io.grpc.alts.internal.Handshaker.StartClientHandshakeReq();
-    }
-
-    public static io.grpc.alts.internal.Handshaker.StartClientHandshakeReq getDefaultInstance() {
-      return DEFAULT_INSTANCE;
-    }
-
-    private static final com.google.protobuf.Parser<StartClientHandshakeReq>
-        PARSER = new com.google.protobuf.AbstractParser<StartClientHandshakeReq>() {
-      public StartClientHandshakeReq parsePartialFrom(
-          com.google.protobuf.CodedInputStream input,
-          com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-          throws com.google.protobuf.InvalidProtocolBufferException {
-        return new StartClientHandshakeReq(input, extensionRegistry);
-      }
-    };
-
-    public static com.google.protobuf.Parser<StartClientHandshakeReq> parser() {
-      return PARSER;
-    }
-
-    @java.lang.Override
-    public com.google.protobuf.Parser<StartClientHandshakeReq> getParserForType() {
-      return PARSER;
-    }
-
-    public io.grpc.alts.internal.Handshaker.StartClientHandshakeReq getDefaultInstanceForType() {
-      return DEFAULT_INSTANCE;
-    }
-
-  }
-
-  public interface ServerHandshakeParametersOrBuilder extends
-      // @@protoc_insertion_point(interface_extends:grpc.gcp.ServerHandshakeParameters)
-      com.google.protobuf.MessageOrBuilder {
-
-    /**
-     * <pre>
-     * The record protocols supported by the server, e.g.,
-     * "ALTSRP_GCM_AES128".
-     * </pre>
-     *
-     * <code>repeated string record_protocols = 1;</code>
-     */
-    java.util.List<java.lang.String>
-        getRecordProtocolsList();
-    /**
-     * <pre>
-     * The record protocols supported by the server, e.g.,
-     * "ALTSRP_GCM_AES128".
-     * </pre>
-     *
-     * <code>repeated string record_protocols = 1;</code>
-     */
-    int getRecordProtocolsCount();
-    /**
-     * <pre>
-     * The record protocols supported by the server, e.g.,
-     * "ALTSRP_GCM_AES128".
-     * </pre>
-     *
-     * <code>repeated string record_protocols = 1;</code>
-     */
-    java.lang.String getRecordProtocols(int index);
-    /**
-     * <pre>
-     * The record protocols supported by the server, e.g.,
-     * "ALTSRP_GCM_AES128".
-     * </pre>
-     *
-     * <code>repeated string record_protocols = 1;</code>
-     */
-    com.google.protobuf.ByteString
-        getRecordProtocolsBytes(int index);
-
-    /**
-     * <pre>
-     * (Optional) A list of local identities supported by the server, if
-     * specified. Otherwise, the handshaker chooses a default local identity.
-     * </pre>
-     *
-     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-     */
-    java.util.List<io.grpc.alts.internal.Handshaker.Identity> 
-        getLocalIdentitiesList();
-    /**
-     * <pre>
-     * (Optional) A list of local identities supported by the server, if
-     * specified. Otherwise, the handshaker chooses a default local identity.
-     * </pre>
-     *
-     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-     */
-    io.grpc.alts.internal.Handshaker.Identity getLocalIdentities(int index);
-    /**
-     * <pre>
-     * (Optional) A list of local identities supported by the server, if
-     * specified. Otherwise, the handshaker chooses a default local identity.
-     * </pre>
-     *
-     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-     */
-    int getLocalIdentitiesCount();
-    /**
-     * <pre>
-     * (Optional) A list of local identities supported by the server, if
-     * specified. Otherwise, the handshaker chooses a default local identity.
-     * </pre>
-     *
-     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-     */
-    java.util.List<? extends io.grpc.alts.internal.Handshaker.IdentityOrBuilder> 
-        getLocalIdentitiesOrBuilderList();
-    /**
-     * <pre>
-     * (Optional) A list of local identities supported by the server, if
-     * specified. Otherwise, the handshaker chooses a default local identity.
-     * </pre>
-     *
-     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-     */
-    io.grpc.alts.internal.Handshaker.IdentityOrBuilder getLocalIdentitiesOrBuilder(
-        int index);
-  }
-  /**
-   * Protobuf type {@code grpc.gcp.ServerHandshakeParameters}
-   */
-  public  static final class ServerHandshakeParameters extends
-      com.google.protobuf.GeneratedMessageV3 implements
-      // @@protoc_insertion_point(message_implements:grpc.gcp.ServerHandshakeParameters)
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-      super(builder);
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-        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-        throws com.google.protobuf.InvalidProtocolBufferException {
-      this();
-      if (extensionRegistry == null) {
-        throw new java.lang.NullPointerException();
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-              if (!((mutable_bitField0_ & 0x00000001) == 0x00000001)) {
-                recordProtocols_ = new com.google.protobuf.LazyStringArrayList();
-                mutable_bitField0_ |= 0x00000001;
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-              recordProtocols_.add(s);
-              break;
-            }
-            case 18: {
-              if (!((mutable_bitField0_ & 0x00000002) == 0x00000002)) {
-                localIdentities_ = new java.util.ArrayList<io.grpc.alts.internal.Handshaker.Identity>();
-                mutable_bitField0_ |= 0x00000002;
-              }
-              localIdentities_.add(
-                  input.readMessage(io.grpc.alts.internal.Handshaker.Identity.parser(), extensionRegistry));
-              break;
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-      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
-        throw e.setUnfinishedMessage(this);
-      } catch (java.io.IOException e) {
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-        this.unknownFields = unknownFields.build();
-        makeExtensionsImmutable();
-      }
-    }
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-    }
-
-    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
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-    public static final int RECORD_PROTOCOLS_FIELD_NUMBER = 1;
-    private com.google.protobuf.LazyStringList recordProtocols_;
-    /**
-     * <pre>
-     * The record protocols supported by the server, e.g.,
-     * "ALTSRP_GCM_AES128".
-     * </pre>
-     *
-     * <code>repeated string record_protocols = 1;</code>
-     */
-    public com.google.protobuf.ProtocolStringList
-        getRecordProtocolsList() {
-      return recordProtocols_;
-    }
-    /**
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-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-       */
-      public Builder setLocalIdentities(
-          int index, io.grpc.alts.internal.Handshaker.Identity value) {
-        if (localIdentitiesBuilder_ == null) {
-          if (value == null) {
-            throw new NullPointerException();
-          }
-          ensureLocalIdentitiesIsMutable();
-          localIdentities_.set(index, value);
-          onChanged();
-        } else {
-          localIdentitiesBuilder_.setMessage(index, value);
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) A list of local identities supported by the server, if
-       * specified. Otherwise, the handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-       */
-      public Builder setLocalIdentities(
-          int index, io.grpc.alts.internal.Handshaker.Identity.Builder builderForValue) {
-        if (localIdentitiesBuilder_ == null) {
-          ensureLocalIdentitiesIsMutable();
-          localIdentities_.set(index, builderForValue.build());
-          onChanged();
-        } else {
-          localIdentitiesBuilder_.setMessage(index, builderForValue.build());
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) A list of local identities supported by the server, if
-       * specified. Otherwise, the handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-       */
-      public Builder addLocalIdentities(io.grpc.alts.internal.Handshaker.Identity value) {
-        if (localIdentitiesBuilder_ == null) {
-          if (value == null) {
-            throw new NullPointerException();
-          }
-          ensureLocalIdentitiesIsMutable();
-          localIdentities_.add(value);
-          onChanged();
-        } else {
-          localIdentitiesBuilder_.addMessage(value);
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) A list of local identities supported by the server, if
-       * specified. Otherwise, the handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-       */
-      public Builder addLocalIdentities(
-          int index, io.grpc.alts.internal.Handshaker.Identity value) {
-        if (localIdentitiesBuilder_ == null) {
-          if (value == null) {
-            throw new NullPointerException();
-          }
-          ensureLocalIdentitiesIsMutable();
-          localIdentities_.add(index, value);
-          onChanged();
-        } else {
-          localIdentitiesBuilder_.addMessage(index, value);
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) A list of local identities supported by the server, if
-       * specified. Otherwise, the handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-       */
-      public Builder addLocalIdentities(
-          io.grpc.alts.internal.Handshaker.Identity.Builder builderForValue) {
-        if (localIdentitiesBuilder_ == null) {
-          ensureLocalIdentitiesIsMutable();
-          localIdentities_.add(builderForValue.build());
-          onChanged();
-        } else {
-          localIdentitiesBuilder_.addMessage(builderForValue.build());
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) A list of local identities supported by the server, if
-       * specified. Otherwise, the handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-       */
-      public Builder addLocalIdentities(
-          int index, io.grpc.alts.internal.Handshaker.Identity.Builder builderForValue) {
-        if (localIdentitiesBuilder_ == null) {
-          ensureLocalIdentitiesIsMutable();
-          localIdentities_.add(index, builderForValue.build());
-          onChanged();
-        } else {
-          localIdentitiesBuilder_.addMessage(index, builderForValue.build());
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) A list of local identities supported by the server, if
-       * specified. Otherwise, the handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-       */
-      public Builder addAllLocalIdentities(
-          java.lang.Iterable<? extends io.grpc.alts.internal.Handshaker.Identity> values) {
-        if (localIdentitiesBuilder_ == null) {
-          ensureLocalIdentitiesIsMutable();
-          com.google.protobuf.AbstractMessageLite.Builder.addAll(
-              values, localIdentities_);
-          onChanged();
-        } else {
-          localIdentitiesBuilder_.addAllMessages(values);
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) A list of local identities supported by the server, if
-       * specified. Otherwise, the handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-       */
-      public Builder clearLocalIdentities() {
-        if (localIdentitiesBuilder_ == null) {
-          localIdentities_ = java.util.Collections.emptyList();
-          bitField0_ = (bitField0_ & ~0x00000002);
-          onChanged();
-        } else {
-          localIdentitiesBuilder_.clear();
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) A list of local identities supported by the server, if
-       * specified. Otherwise, the handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-       */
-      public Builder removeLocalIdentities(int index) {
-        if (localIdentitiesBuilder_ == null) {
-          ensureLocalIdentitiesIsMutable();
-          localIdentities_.remove(index);
-          onChanged();
-        } else {
-          localIdentitiesBuilder_.remove(index);
-        }
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) A list of local identities supported by the server, if
-       * specified. Otherwise, the handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.Identity.Builder getLocalIdentitiesBuilder(
-          int index) {
-        return getLocalIdentitiesFieldBuilder().getBuilder(index);
-      }
-      /**
-       * <pre>
-       * (Optional) A list of local identities supported by the server, if
-       * specified. Otherwise, the handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.IdentityOrBuilder getLocalIdentitiesOrBuilder(
-          int index) {
-        if (localIdentitiesBuilder_ == null) {
-          return localIdentities_.get(index);  } else {
-          return localIdentitiesBuilder_.getMessageOrBuilder(index);
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) A list of local identities supported by the server, if
-       * specified. Otherwise, the handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-       */
-      public java.util.List<? extends io.grpc.alts.internal.Handshaker.IdentityOrBuilder> 
-           getLocalIdentitiesOrBuilderList() {
-        if (localIdentitiesBuilder_ != null) {
-          return localIdentitiesBuilder_.getMessageOrBuilderList();
-        } else {
-          return java.util.Collections.unmodifiableList(localIdentities_);
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) A list of local identities supported by the server, if
-       * specified. Otherwise, the handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.Identity.Builder addLocalIdentitiesBuilder() {
-        return getLocalIdentitiesFieldBuilder().addBuilder(
-            io.grpc.alts.internal.Handshaker.Identity.getDefaultInstance());
-      }
-      /**
-       * <pre>
-       * (Optional) A list of local identities supported by the server, if
-       * specified. Otherwise, the handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.Identity.Builder addLocalIdentitiesBuilder(
-          int index) {
-        return getLocalIdentitiesFieldBuilder().addBuilder(
-            index, io.grpc.alts.internal.Handshaker.Identity.getDefaultInstance());
-      }
-      /**
-       * <pre>
-       * (Optional) A list of local identities supported by the server, if
-       * specified. Otherwise, the handshaker chooses a default local identity.
-       * </pre>
-       *
-       * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
-       */
-      public java.util.List<io.grpc.alts.internal.Handshaker.Identity.Builder> 
-           getLocalIdentitiesBuilderList() {
-        return getLocalIdentitiesFieldBuilder().getBuilderList();
-      }
-      private com.google.protobuf.RepeatedFieldBuilderV3<
-          io.grpc.alts.internal.Handshaker.Identity, io.grpc.alts.internal.Handshaker.Identity.Builder, io.grpc.alts.internal.Handshaker.IdentityOrBuilder> 
-          getLocalIdentitiesFieldBuilder() {
-        if (localIdentitiesBuilder_ == null) {
-          localIdentitiesBuilder_ = new com.google.protobuf.RepeatedFieldBuilderV3<
-              io.grpc.alts.internal.Handshaker.Identity, io.grpc.alts.internal.Handshaker.Identity.Builder, io.grpc.alts.internal.Handshaker.IdentityOrBuilder>(
-                  localIdentities_,
-                  ((bitField0_ & 0x00000002) == 0x00000002),
-                  getParentForChildren(),
-                  isClean());
-          localIdentities_ = null;
-        }
-        return localIdentitiesBuilder_;
-      }
-      public final Builder setUnknownFields(
-          final com.google.protobuf.UnknownFieldSet unknownFields) {
-        return super.setUnknownFieldsProto3(unknownFields);
-      }
-
-      public final Builder mergeUnknownFields(
-          final com.google.protobuf.UnknownFieldSet unknownFields) {
-        return super.mergeUnknownFields(unknownFields);
-      }
-
-
-      // @@protoc_insertion_point(builder_scope:grpc.gcp.ServerHandshakeParameters)
-    }
-
-    // @@protoc_insertion_point(class_scope:grpc.gcp.ServerHandshakeParameters)
-    private static final io.grpc.alts.internal.Handshaker.ServerHandshakeParameters DEFAULT_INSTANCE;
-    static {
-      DEFAULT_INSTANCE = new io.grpc.alts.internal.Handshaker.ServerHandshakeParameters();
-    }
-
-    public static io.grpc.alts.internal.Handshaker.ServerHandshakeParameters getDefaultInstance() {
-      return DEFAULT_INSTANCE;
-    }
-
-    private static final com.google.protobuf.Parser<ServerHandshakeParameters>
-        PARSER = new com.google.protobuf.AbstractParser<ServerHandshakeParameters>() {
-      public ServerHandshakeParameters parsePartialFrom(
-          com.google.protobuf.CodedInputStream input,
-          com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-          throws com.google.protobuf.InvalidProtocolBufferException {
-        return new ServerHandshakeParameters(input, extensionRegistry);
-      }
-    };
-
-    public static com.google.protobuf.Parser<ServerHandshakeParameters> parser() {
-      return PARSER;
-    }
-
-    @java.lang.Override
-    public com.google.protobuf.Parser<ServerHandshakeParameters> getParserForType() {
-      return PARSER;
-    }
-
-    public io.grpc.alts.internal.Handshaker.ServerHandshakeParameters getDefaultInstanceForType() {
-      return DEFAULT_INSTANCE;
-    }
-
-  }
-
-  public interface StartServerHandshakeReqOrBuilder extends
-      // @@protoc_insertion_point(interface_extends:grpc.gcp.StartServerHandshakeReq)
-      com.google.protobuf.MessageOrBuilder {
-
-    /**
-     * <pre>
-     * The application protocols supported by the server, e.g., "h2" (for http2),
-     * "grpc".
-     * </pre>
-     *
-     * <code>repeated string application_protocols = 1;</code>
-     */
-    java.util.List<java.lang.String>
-        getApplicationProtocolsList();
-    /**
-     * <pre>
-     * The application protocols supported by the server, e.g., "h2" (for http2),
-     * "grpc".
-     * </pre>
-     *
-     * <code>repeated string application_protocols = 1;</code>
-     */
-    int getApplicationProtocolsCount();
-    /**
-     * <pre>
-     * The application protocols supported by the server, e.g., "h2" (for http2),
-     * "grpc".
-     * </pre>
-     *
-     * <code>repeated string application_protocols = 1;</code>
-     */
-    java.lang.String getApplicationProtocols(int index);
-    /**
-     * <pre>
-     * The application protocols supported by the server, e.g., "h2" (for http2),
-     * "grpc".
-     * </pre>
-     *
-     * <code>repeated string application_protocols = 1;</code>
-     */
-    com.google.protobuf.ByteString
-        getApplicationProtocolsBytes(int index);
-
-    /**
-     * <pre>
-     * Handshake parameters (record protocols and local identities supported by
-     * the server) mapped by the handshake protocol. Each handshake security
-     * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
-     * identities. Since protobuf does not support enum as key to the map, the key
-     * to handshake_parameters is the integer value of HandshakeProtocol enum.
-     * </pre>
-     *
-     * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
-     */
-    int getHandshakeParametersCount();
-    /**
-     * <pre>
-     * Handshake parameters (record protocols and local identities supported by
-     * the server) mapped by the handshake protocol. Each handshake security
-     * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
-     * identities. Since protobuf does not support enum as key to the map, the key
-     * to handshake_parameters is the integer value of HandshakeProtocol enum.
-     * </pre>
-     *
-     * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
-     */
-    boolean containsHandshakeParameters(
-        int key);
-    /**
-     * Use {@link #getHandshakeParametersMap()} instead.
-     */
-    @java.lang.Deprecated
-    java.util.Map<java.lang.Integer, io.grpc.alts.internal.Handshaker.ServerHandshakeParameters>
-    getHandshakeParameters();
-    /**
-     * <pre>
-     * Handshake parameters (record protocols and local identities supported by
-     * the server) mapped by the handshake protocol. Each handshake security
-     * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
-     * identities. Since protobuf does not support enum as key to the map, the key
-     * to handshake_parameters is the integer value of HandshakeProtocol enum.
-     * </pre>
-     *
-     * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
-     */
-    java.util.Map<java.lang.Integer, io.grpc.alts.internal.Handshaker.ServerHandshakeParameters>
-    getHandshakeParametersMap();
-    /**
-     * <pre>
-     * Handshake parameters (record protocols and local identities supported by
-     * the server) mapped by the handshake protocol. Each handshake security
-     * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
-     * identities. Since protobuf does not support enum as key to the map, the key
-     * to handshake_parameters is the integer value of HandshakeProtocol enum.
-     * </pre>
-     *
-     * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
-     */
-
-    io.grpc.alts.internal.Handshaker.ServerHandshakeParameters getHandshakeParametersOrDefault(
-        int key,
-        io.grpc.alts.internal.Handshaker.ServerHandshakeParameters defaultValue);
-    /**
-     * <pre>
-     * Handshake parameters (record protocols and local identities supported by
-     * the server) mapped by the handshake protocol. Each handshake security
-     * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
-     * identities. Since protobuf does not support enum as key to the map, the key
-     * to handshake_parameters is the integer value of HandshakeProtocol enum.
-     * </pre>
-     *
-     * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
-     */
-
-    io.grpc.alts.internal.Handshaker.ServerHandshakeParameters getHandshakeParametersOrThrow(
-        int key);
-
-    /**
-     * <pre>
-     * Bytes in out_frames returned from the peer's HandshakerResp. It is possible
-     * that the peer's out_frames are split into multiple HandshakReq messages.
-     * </pre>
-     *
-     * <code>bytes in_bytes = 3;</code>
-     */
-    com.google.protobuf.ByteString getInBytes();
-
-    /**
-     * <pre>
-     * (Optional) Local endpoint information of the connection to the client,
-     * such as local IP address, port number, and network protocol.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
-     */
-    boolean hasLocalEndpoint();
-    /**
-     * <pre>
-     * (Optional) Local endpoint information of the connection to the client,
-     * such as local IP address, port number, and network protocol.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
-     */
-    io.grpc.alts.internal.Handshaker.Endpoint getLocalEndpoint();
-    /**
-     * <pre>
-     * (Optional) Local endpoint information of the connection to the client,
-     * such as local IP address, port number, and network protocol.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
-     */
-    io.grpc.alts.internal.Handshaker.EndpointOrBuilder getLocalEndpointOrBuilder();
-
-    /**
-     * <pre>
-     * (Optional) Endpoint information of the remote client, such as IP address,
-     * port number, and network protocol.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
-     */
-    boolean hasRemoteEndpoint();
-    /**
-     * <pre>
-     * (Optional) Endpoint information of the remote client, such as IP address,
-     * port number, and network protocol.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
-     */
-    io.grpc.alts.internal.Handshaker.Endpoint getRemoteEndpoint();
-    /**
-     * <pre>
-     * (Optional) Endpoint information of the remote client, such as IP address,
-     * port number, and network protocol.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
-     */
-    io.grpc.alts.internal.Handshaker.EndpointOrBuilder getRemoteEndpointOrBuilder();
-
-    /**
-     * <pre>
-     * (Optional) RPC protocol versions supported by the server.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 6;</code>
-     */
-    boolean hasRpcVersions();
-    /**
-     * <pre>
-     * (Optional) RPC protocol versions supported by the server.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 6;</code>
-     */
-    io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions getRpcVersions();
-    /**
-     * <pre>
-     * (Optional) RPC protocol versions supported by the server.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 6;</code>
-     */
-    io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersionsOrBuilder getRpcVersionsOrBuilder();
-  }
-  /**
-   * Protobuf type {@code grpc.gcp.StartServerHandshakeReq}
-   */
-  public  static final class StartServerHandshakeReq extends
-      com.google.protobuf.GeneratedMessageV3 implements
-      // @@protoc_insertion_point(message_implements:grpc.gcp.StartServerHandshakeReq)
-      StartServerHandshakeReqOrBuilder {
-  private static final long serialVersionUID = 0L;
-    // Use StartServerHandshakeReq.newBuilder() to construct.
-    private StartServerHandshakeReq(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
-      super(builder);
-    }
-    private StartServerHandshakeReq() {
-      applicationProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
-      inBytes_ = com.google.protobuf.ByteString.EMPTY;
-    }
-
-    @java.lang.Override
-    public final com.google.protobuf.UnknownFieldSet
-    getUnknownFields() {
-      return this.unknownFields;
-    }
-    private StartServerHandshakeReq(
-        com.google.protobuf.CodedInputStream input,
-        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-        throws com.google.protobuf.InvalidProtocolBufferException {
-      this();
-      if (extensionRegistry == null) {
-        throw new java.lang.NullPointerException();
-      }
-      int mutable_bitField0_ = 0;
-      com.google.protobuf.UnknownFieldSet.Builder unknownFields =
-          com.google.protobuf.UnknownFieldSet.newBuilder();
-      try {
-        boolean done = false;
-        while (!done) {
-          int tag = input.readTag();
-          switch (tag) {
-            case 0:
-              done = true;
-              break;
-            default: {
-              if (!parseUnknownFieldProto3(
-                  input, unknownFields, extensionRegistry, tag)) {
-                done = true;
-              }
-              break;
-            }
-            case 10: {
-              java.lang.String s = input.readStringRequireUtf8();
-              if (!((mutable_bitField0_ & 0x00000001) == 0x00000001)) {
-                applicationProtocols_ = new com.google.protobuf.LazyStringArrayList();
-                mutable_bitField0_ |= 0x00000001;
-              }
-              applicationProtocols_.add(s);
-              break;
-            }
-            case 18: {
-              if (!((mutable_bitField0_ & 0x00000002) == 0x00000002)) {
-                handshakeParameters_ = com.google.protobuf.MapField.newMapField(
-                    HandshakeParametersDefaultEntryHolder.defaultEntry);
-                mutable_bitField0_ |= 0x00000002;
-              }
-              com.google.protobuf.MapEntry<java.lang.Integer, io.grpc.alts.internal.Handshaker.ServerHandshakeParameters>
-              handshakeParameters__ = input.readMessage(
-                  HandshakeParametersDefaultEntryHolder.defaultEntry.getParserForType(), extensionRegistry);
-              handshakeParameters_.getMutableMap().put(
-                  handshakeParameters__.getKey(), handshakeParameters__.getValue());
-              break;
-            }
-            case 26: {
-
-              inBytes_ = input.readBytes();
-              break;
-            }
-            case 34: {
-              io.grpc.alts.internal.Handshaker.Endpoint.Builder subBuilder = null;
-              if (localEndpoint_ != null) {
-                subBuilder = localEndpoint_.toBuilder();
-              }
-              localEndpoint_ = input.readMessage(io.grpc.alts.internal.Handshaker.Endpoint.parser(), extensionRegistry);
-              if (subBuilder != null) {
-                subBuilder.mergeFrom(localEndpoint_);
-                localEndpoint_ = subBuilder.buildPartial();
-              }
-
-              break;
-            }
-            case 42: {
-              io.grpc.alts.internal.Handshaker.Endpoint.Builder subBuilder = null;
-              if (remoteEndpoint_ != null) {
-                subBuilder = remoteEndpoint_.toBuilder();
-              }
-              remoteEndpoint_ = input.readMessage(io.grpc.alts.internal.Handshaker.Endpoint.parser(), extensionRegistry);
-              if (subBuilder != null) {
-                subBuilder.mergeFrom(remoteEndpoint_);
-                remoteEndpoint_ = subBuilder.buildPartial();
-              }
-
-              break;
-            }
-            case 50: {
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Builder subBuilder = null;
-              if (rpcVersions_ != null) {
-                subBuilder = rpcVersions_.toBuilder();
-              }
-              rpcVersions_ = input.readMessage(io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.parser(), extensionRegistry);
-              if (subBuilder != null) {
-                subBuilder.mergeFrom(rpcVersions_);
-                rpcVersions_ = subBuilder.buildPartial();
-              }
-
-              break;
-            }
-          }
-        }
-      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
-        throw e.setUnfinishedMessage(this);
-      } catch (java.io.IOException e) {
-        throw new com.google.protobuf.InvalidProtocolBufferException(
-            e).setUnfinishedMessage(this);
-      } finally {
-        if (((mutable_bitField0_ & 0x00000001) == 0x00000001)) {
-          applicationProtocols_ = applicationProtocols_.getUnmodifiableView();
-        }
-        this.unknownFields = unknownFields.build();
-        makeExtensionsImmutable();
-      }
-    }
-    public static final com.google.protobuf.Descriptors.Descriptor
-        getDescriptor() {
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-    /**
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-     * "grpc".
-     * </pre>
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-     * <pre>
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-    /**
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-    }
-    /**
-     * <pre>
-     * Handshake parameters (record protocols and local identities supported by
-     * the server) mapped by the handshake protocol. Each handshake security
-     * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
-     * identities. Since protobuf does not support enum as key to the map, the key
-     * to handshake_parameters is the integer value of HandshakeProtocol enum.
-     * </pre>
-     *
-     * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
-     */
-
-    public boolean containsHandshakeParameters(
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-      
-      return internalGetHandshakeParameters().getMap().containsKey(key);
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-     */
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-    public java.util.Map<java.lang.Integer, io.grpc.alts.internal.Handshaker.ServerHandshakeParameters> getHandshakeParameters() {
-      return getHandshakeParametersMap();
-    }
-    /**
-     * <pre>
-     * Handshake parameters (record protocols and local identities supported by
-     * the server) mapped by the handshake protocol. Each handshake security
-     * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
-     * identities. Since protobuf does not support enum as key to the map, the key
-     * to handshake_parameters is the integer value of HandshakeProtocol enum.
-     * </pre>
-     *
-     * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
-     */
-
-    public java.util.Map<java.lang.Integer, io.grpc.alts.internal.Handshaker.ServerHandshakeParameters> getHandshakeParametersMap() {
-      return internalGetHandshakeParameters().getMap();
-    }
-    /**
-     * <pre>
-     * Handshake parameters (record protocols and local identities supported by
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-     * to handshake_parameters is the integer value of HandshakeProtocol enum.
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-     * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
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-
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-    /**
-     * <pre>
-     * Handshake parameters (record protocols and local identities supported by
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-     * identities. Since protobuf does not support enum as key to the map, the key
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-     * </pre>
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-     * </pre>
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-     * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
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-    public static final int REMOTE_ENDPOINT_FIELD_NUMBER = 5;
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-     * </pre>
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-     * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
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-     * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
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-     * </pre>
-     *
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-     * </pre>
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-      public com.google.protobuf.Descriptors.Descriptor
-          getDescriptorForType() {
-        return io.grpc.alts.internal.Handshaker.internal_static_grpc_gcp_StartServerHandshakeReq_descriptor;
-      }
-
-      public io.grpc.alts.internal.Handshaker.StartServerHandshakeReq getDefaultInstanceForType() {
-        return io.grpc.alts.internal.Handshaker.StartServerHandshakeReq.getDefaultInstance();
-      }
-
-      public io.grpc.alts.internal.Handshaker.StartServerHandshakeReq build() {
-        io.grpc.alts.internal.Handshaker.StartServerHandshakeReq result = buildPartial();
-        if (!result.isInitialized()) {
-          throw newUninitializedMessageException(result);
-        }
-        return result;
-      }
-
-      public io.grpc.alts.internal.Handshaker.StartServerHandshakeReq buildPartial() {
-        io.grpc.alts.internal.Handshaker.StartServerHandshakeReq result = new io.grpc.alts.internal.Handshaker.StartServerHandshakeReq(this);
-        int from_bitField0_ = bitField0_;
-        int to_bitField0_ = 0;
-        if (((bitField0_ & 0x00000001) == 0x00000001)) {
-          applicationProtocols_ = applicationProtocols_.getUnmodifiableView();
-          bitField0_ = (bitField0_ & ~0x00000001);
-        }
-        result.applicationProtocols_ = applicationProtocols_;
-        result.handshakeParameters_ = internalGetHandshakeParameters();
-        result.handshakeParameters_.makeImmutable();
-        result.inBytes_ = inBytes_;
-        if (localEndpointBuilder_ == null) {
-          result.localEndpoint_ = localEndpoint_;
-        } else {
-          result.localEndpoint_ = localEndpointBuilder_.build();
-        }
-        if (remoteEndpointBuilder_ == null) {
-          result.remoteEndpoint_ = remoteEndpoint_;
-        } else {
-          result.remoteEndpoint_ = remoteEndpointBuilder_.build();
-        }
-        if (rpcVersionsBuilder_ == null) {
-          result.rpcVersions_ = rpcVersions_;
-        } else {
-          result.rpcVersions_ = rpcVersionsBuilder_.build();
-        }
-        result.bitField0_ = to_bitField0_;
-        onBuilt();
-        return result;
-      }
-
-      public Builder clone() {
-        return (Builder) super.clone();
-      }
-      public Builder setField(
-          com.google.protobuf.Descriptors.FieldDescriptor field,
-          java.lang.Object value) {
-        return (Builder) super.setField(field, value);
-      }
-      public Builder clearField(
-          com.google.protobuf.Descriptors.FieldDescriptor field) {
-        return (Builder) super.clearField(field);
-      }
-      public Builder clearOneof(
-          com.google.protobuf.Descriptors.OneofDescriptor oneof) {
-        return (Builder) super.clearOneof(oneof);
-      }
-      public Builder setRepeatedField(
-          com.google.protobuf.Descriptors.FieldDescriptor field,
-          int index, java.lang.Object value) {
-        return (Builder) super.setRepeatedField(field, index, value);
-      }
-      public Builder addRepeatedField(
-          com.google.protobuf.Descriptors.FieldDescriptor field,
-          java.lang.Object value) {
-        return (Builder) super.addRepeatedField(field, value);
-      }
-      public Builder mergeFrom(com.google.protobuf.Message other) {
-        if (other instanceof io.grpc.alts.internal.Handshaker.StartServerHandshakeReq) {
-          return mergeFrom((io.grpc.alts.internal.Handshaker.StartServerHandshakeReq)other);
-        } else {
-          super.mergeFrom(other);
-          return this;
-        }
-      }
-
-      public Builder mergeFrom(io.grpc.alts.internal.Handshaker.StartServerHandshakeReq other) {
-        if (other == io.grpc.alts.internal.Handshaker.StartServerHandshakeReq.getDefaultInstance()) return this;
-        if (!other.applicationProtocols_.isEmpty()) {
-          if (applicationProtocols_.isEmpty()) {
-            applicationProtocols_ = other.applicationProtocols_;
-            bitField0_ = (bitField0_ & ~0x00000001);
-          } else {
-            ensureApplicationProtocolsIsMutable();
-            applicationProtocols_.addAll(other.applicationProtocols_);
-          }
-          onChanged();
-        }
-        internalGetMutableHandshakeParameters().mergeFrom(
-            other.internalGetHandshakeParameters());
-        if (other.getInBytes() != com.google.protobuf.ByteString.EMPTY) {
-          setInBytes(other.getInBytes());
-        }
-        if (other.hasLocalEndpoint()) {
-          mergeLocalEndpoint(other.getLocalEndpoint());
-        }
-        if (other.hasRemoteEndpoint()) {
-          mergeRemoteEndpoint(other.getRemoteEndpoint());
-        }
-        if (other.hasRpcVersions()) {
-          mergeRpcVersions(other.getRpcVersions());
-        }
-        this.mergeUnknownFields(other.unknownFields);
-        onChanged();
-        return this;
-      }
-
-      public final boolean isInitialized() {
-        return true;
-      }
-
-      public Builder mergeFrom(
-          com.google.protobuf.CodedInputStream input,
-          com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-          throws java.io.IOException {
-        io.grpc.alts.internal.Handshaker.StartServerHandshakeReq parsedMessage = null;
-        try {
-          parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);
-        } catch (com.google.protobuf.InvalidProtocolBufferException e) {
-          parsedMessage = (io.grpc.alts.internal.Handshaker.StartServerHandshakeReq) e.getUnfinishedMessage();
-          throw e.unwrapIOException();
-        } finally {
-          if (parsedMessage != null) {
-            mergeFrom(parsedMessage);
-          }
-        }
-        return this;
-      }
-      private int bitField0_;
-
-      private com.google.protobuf.LazyStringList applicationProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
-      private void ensureApplicationProtocolsIsMutable() {
-        if (!((bitField0_ & 0x00000001) == 0x00000001)) {
-          applicationProtocols_ = new com.google.protobuf.LazyStringArrayList(applicationProtocols_);
-          bitField0_ |= 0x00000001;
-         }
-      }
-      /**
-       * <pre>
-       * The application protocols supported by the server, e.g., "h2" (for http2),
-       * "grpc".
-       * </pre>
-       *
-       * <code>repeated string application_protocols = 1;</code>
-       */
-      public com.google.protobuf.ProtocolStringList
-          getApplicationProtocolsList() {
-        return applicationProtocols_.getUnmodifiableView();
-      }
-      /**
-       * <pre>
-       * The application protocols supported by the server, e.g., "h2" (for http2),
-       * "grpc".
-       * </pre>
-       *
-       * <code>repeated string application_protocols = 1;</code>
-       */
-      public int getApplicationProtocolsCount() {
-        return applicationProtocols_.size();
-      }
-      /**
-       * <pre>
-       * The application protocols supported by the server, e.g., "h2" (for http2),
-       * "grpc".
-       * </pre>
-       *
-       * <code>repeated string application_protocols = 1;</code>
-       */
-      public java.lang.String getApplicationProtocols(int index) {
-        return applicationProtocols_.get(index);
-      }
-      /**
-       * <pre>
-       * The application protocols supported by the server, e.g., "h2" (for http2),
-       * "grpc".
-       * </pre>
-       *
-       * <code>repeated string application_protocols = 1;</code>
-       */
-      public com.google.protobuf.ByteString
-          getApplicationProtocolsBytes(int index) {
-        return applicationProtocols_.getByteString(index);
-      }
-      /**
-       * <pre>
-       * The application protocols supported by the server, e.g., "h2" (for http2),
-       * "grpc".
-       * </pre>
-       *
-       * <code>repeated string application_protocols = 1;</code>
-       */
-      public Builder setApplicationProtocols(
-          int index, java.lang.String value) {
-        if (value == null) {
-    throw new NullPointerException();
-  }
-  ensureApplicationProtocolsIsMutable();
-        applicationProtocols_.set(index, value);
-        onChanged();
-        return this;
-      }
-      /**
-       * <pre>
-       * The application protocols supported by the server, e.g., "h2" (for http2),
-       * "grpc".
-       * </pre>
-       *
-       * <code>repeated string application_protocols = 1;</code>
-       */
-      public Builder addApplicationProtocols(
-          java.lang.String value) {
-        if (value == null) {
-    throw new NullPointerException();
-  }
-  ensureApplicationProtocolsIsMutable();
-        applicationProtocols_.add(value);
-        onChanged();
-        return this;
-      }
-      /**
-       * <pre>
-       * The application protocols supported by the server, e.g., "h2" (for http2),
-       * "grpc".
-       * </pre>
-       *
-       * <code>repeated string application_protocols = 1;</code>
-       */
-      public Builder addAllApplicationProtocols(
-          java.lang.Iterable<java.lang.String> values) {
-        ensureApplicationProtocolsIsMutable();
-        com.google.protobuf.AbstractMessageLite.Builder.addAll(
-            values, applicationProtocols_);
-        onChanged();
-        return this;
-      }
-      /**
-       * <pre>
-       * The application protocols supported by the server, e.g., "h2" (for http2),
-       * "grpc".
-       * </pre>
-       *
-       * <code>repeated string application_protocols = 1;</code>
-       */
-      public Builder clearApplicationProtocols() {
-        applicationProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
-        bitField0_ = (bitField0_ & ~0x00000001);
-        onChanged();
-        return this;
-      }
-      /**
-       * <pre>
-       * The application protocols supported by the server, e.g., "h2" (for http2),
-       * "grpc".
-       * </pre>
-       *
-       * <code>repeated string application_protocols = 1;</code>
-       */
-      public Builder addApplicationProtocolsBytes(
-          com.google.protobuf.ByteString value) {
-        if (value == null) {
-    throw new NullPointerException();
-  }
-  checkByteStringIsUtf8(value);
-        ensureApplicationProtocolsIsMutable();
-        applicationProtocols_.add(value);
-        onChanged();
-        return this;
-      }
-
-      private com.google.protobuf.MapField<
-          java.lang.Integer, io.grpc.alts.internal.Handshaker.ServerHandshakeParameters> handshakeParameters_;
-      private com.google.protobuf.MapField<java.lang.Integer, io.grpc.alts.internal.Handshaker.ServerHandshakeParameters>
-      internalGetHandshakeParameters() {
-        if (handshakeParameters_ == null) {
-          return com.google.protobuf.MapField.emptyMapField(
-              HandshakeParametersDefaultEntryHolder.defaultEntry);
-        }
-        return handshakeParameters_;
-      }
-      private com.google.protobuf.MapField<java.lang.Integer, io.grpc.alts.internal.Handshaker.ServerHandshakeParameters>
-      internalGetMutableHandshakeParameters() {
-        onChanged();;
-        if (handshakeParameters_ == null) {
-          handshakeParameters_ = com.google.protobuf.MapField.newMapField(
-              HandshakeParametersDefaultEntryHolder.defaultEntry);
-        }
-        if (!handshakeParameters_.isMutable()) {
-          handshakeParameters_ = handshakeParameters_.copy();
-        }
-        return handshakeParameters_;
-      }
-
-      public int getHandshakeParametersCount() {
-        return internalGetHandshakeParameters().getMap().size();
-      }
-      /**
-       * <pre>
-       * Handshake parameters (record protocols and local identities supported by
-       * the server) mapped by the handshake protocol. Each handshake security
-       * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
-       * identities. Since protobuf does not support enum as key to the map, the key
-       * to handshake_parameters is the integer value of HandshakeProtocol enum.
-       * </pre>
-       *
-       * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
-       */
-
-      public boolean containsHandshakeParameters(
-          int key) {
-        
-        return internalGetHandshakeParameters().getMap().containsKey(key);
-      }
-      /**
-       * Use {@link #getHandshakeParametersMap()} instead.
-       */
-      @java.lang.Deprecated
-      public java.util.Map<java.lang.Integer, io.grpc.alts.internal.Handshaker.ServerHandshakeParameters> getHandshakeParameters() {
-        return getHandshakeParametersMap();
-      }
-      /**
-       * <pre>
-       * Handshake parameters (record protocols and local identities supported by
-       * the server) mapped by the handshake protocol. Each handshake security
-       * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
-       * identities. Since protobuf does not support enum as key to the map, the key
-       * to handshake_parameters is the integer value of HandshakeProtocol enum.
-       * </pre>
-       *
-       * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
-       */
-
-      public java.util.Map<java.lang.Integer, io.grpc.alts.internal.Handshaker.ServerHandshakeParameters> getHandshakeParametersMap() {
-        return internalGetHandshakeParameters().getMap();
-      }
-      /**
-       * <pre>
-       * Handshake parameters (record protocols and local identities supported by
-       * the server) mapped by the handshake protocol. Each handshake security
-       * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
-       * identities. Since protobuf does not support enum as key to the map, the key
-       * to handshake_parameters is the integer value of HandshakeProtocol enum.
-       * </pre>
-       *
-       * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
-       */
-
-      public io.grpc.alts.internal.Handshaker.ServerHandshakeParameters getHandshakeParametersOrDefault(
-          int key,
-          io.grpc.alts.internal.Handshaker.ServerHandshakeParameters defaultValue) {
-        
-        java.util.Map<java.lang.Integer, io.grpc.alts.internal.Handshaker.ServerHandshakeParameters> map =
-            internalGetHandshakeParameters().getMap();
-        return map.containsKey(key) ? map.get(key) : defaultValue;
-      }
-      /**
-       * <pre>
-       * Handshake parameters (record protocols and local identities supported by
-       * the server) mapped by the handshake protocol. Each handshake security
-       * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
-       * identities. Since protobuf does not support enum as key to the map, the key
-       * to handshake_parameters is the integer value of HandshakeProtocol enum.
-       * </pre>
-       *
-       * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
-       */
-
-      public io.grpc.alts.internal.Handshaker.ServerHandshakeParameters getHandshakeParametersOrThrow(
-          int key) {
-        
-        java.util.Map<java.lang.Integer, io.grpc.alts.internal.Handshaker.ServerHandshakeParameters> map =
-            internalGetHandshakeParameters().getMap();
-        if (!map.containsKey(key)) {
-          throw new java.lang.IllegalArgumentException();
-        }
-        return map.get(key);
-      }
-
-      public Builder clearHandshakeParameters() {
-        internalGetMutableHandshakeParameters().getMutableMap()
-            .clear();
-        return this;
-      }
-      /**
-       * <pre>
-       * Handshake parameters (record protocols and local identities supported by
-       * the server) mapped by the handshake protocol. Each handshake security
-       * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
-       * identities. Since protobuf does not support enum as key to the map, the key
-       * to handshake_parameters is the integer value of HandshakeProtocol enum.
-       * </pre>
-       *
-       * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
-       */
-
-      public Builder removeHandshakeParameters(
-          int key) {
-        
-        internalGetMutableHandshakeParameters().getMutableMap()
-            .remove(key);
-        return this;
-      }
-      /**
-       * Use alternate mutation accessors instead.
-       */
-      @java.lang.Deprecated
-      public java.util.Map<java.lang.Integer, io.grpc.alts.internal.Handshaker.ServerHandshakeParameters>
-      getMutableHandshakeParameters() {
-        return internalGetMutableHandshakeParameters().getMutableMap();
-      }
-      /**
-       * <pre>
-       * Handshake parameters (record protocols and local identities supported by
-       * the server) mapped by the handshake protocol. Each handshake security
-       * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
-       * identities. Since protobuf does not support enum as key to the map, the key
-       * to handshake_parameters is the integer value of HandshakeProtocol enum.
-       * </pre>
-       *
-       * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
-       */
-      public Builder putHandshakeParameters(
-          int key,
-          io.grpc.alts.internal.Handshaker.ServerHandshakeParameters value) {
-        
-        if (value == null) { throw new java.lang.NullPointerException(); }
-        internalGetMutableHandshakeParameters().getMutableMap()
-            .put(key, value);
-        return this;
-      }
-      /**
-       * <pre>
-       * Handshake parameters (record protocols and local identities supported by
-       * the server) mapped by the handshake protocol. Each handshake security
-       * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
-       * identities. Since protobuf does not support enum as key to the map, the key
-       * to handshake_parameters is the integer value of HandshakeProtocol enum.
-       * </pre>
-       *
-       * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
-       */
-
-      public Builder putAllHandshakeParameters(
-          java.util.Map<java.lang.Integer, io.grpc.alts.internal.Handshaker.ServerHandshakeParameters> values) {
-        internalGetMutableHandshakeParameters().getMutableMap()
-            .putAll(values);
-        return this;
-      }
-
-      private com.google.protobuf.ByteString inBytes_ = com.google.protobuf.ByteString.EMPTY;
-      /**
-       * <pre>
-       * Bytes in out_frames returned from the peer's HandshakerResp. It is possible
-       * that the peer's out_frames are split into multiple HandshakReq messages.
-       * </pre>
-       *
-       * <code>bytes in_bytes = 3;</code>
-       */
-      public com.google.protobuf.ByteString getInBytes() {
-        return inBytes_;
-      }
-      /**
-       * <pre>
-       * Bytes in out_frames returned from the peer's HandshakerResp. It is possible
-       * that the peer's out_frames are split into multiple HandshakReq messages.
-       * </pre>
-       *
-       * <code>bytes in_bytes = 3;</code>
-       */
-      public Builder setInBytes(com.google.protobuf.ByteString value) {
-        if (value == null) {
-    throw new NullPointerException();
-  }
-  
-        inBytes_ = value;
-        onChanged();
-        return this;
-      }
-      /**
-       * <pre>
-       * Bytes in out_frames returned from the peer's HandshakerResp. It is possible
-       * that the peer's out_frames are split into multiple HandshakReq messages.
-       * </pre>
-       *
-       * <code>bytes in_bytes = 3;</code>
-       */
-      public Builder clearInBytes() {
-        
-        inBytes_ = getDefaultInstance().getInBytes();
-        onChanged();
-        return this;
-      }
-
-      private io.grpc.alts.internal.Handshaker.Endpoint localEndpoint_ = null;
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.Handshaker.Endpoint, io.grpc.alts.internal.Handshaker.Endpoint.Builder, io.grpc.alts.internal.Handshaker.EndpointOrBuilder> localEndpointBuilder_;
-      /**
-       * <pre>
-       * (Optional) Local endpoint information of the connection to the client,
-       * such as local IP address, port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
-       */
-      public boolean hasLocalEndpoint() {
-        return localEndpointBuilder_ != null || localEndpoint_ != null;
-      }
-      /**
-       * <pre>
-       * (Optional) Local endpoint information of the connection to the client,
-       * such as local IP address, port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.Endpoint getLocalEndpoint() {
-        if (localEndpointBuilder_ == null) {
-          return localEndpoint_ == null ? io.grpc.alts.internal.Handshaker.Endpoint.getDefaultInstance() : localEndpoint_;
-        } else {
-          return localEndpointBuilder_.getMessage();
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) Local endpoint information of the connection to the client,
-       * such as local IP address, port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
-       */
-      public Builder setLocalEndpoint(io.grpc.alts.internal.Handshaker.Endpoint value) {
-        if (localEndpointBuilder_ == null) {
-          if (value == null) {
-            throw new NullPointerException();
-          }
-          localEndpoint_ = value;
-          onChanged();
-        } else {
-          localEndpointBuilder_.setMessage(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Local endpoint information of the connection to the client,
-       * such as local IP address, port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
-       */
-      public Builder setLocalEndpoint(
-          io.grpc.alts.internal.Handshaker.Endpoint.Builder builderForValue) {
-        if (localEndpointBuilder_ == null) {
-          localEndpoint_ = builderForValue.build();
-          onChanged();
-        } else {
-          localEndpointBuilder_.setMessage(builderForValue.build());
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Local endpoint information of the connection to the client,
-       * such as local IP address, port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
-       */
-      public Builder mergeLocalEndpoint(io.grpc.alts.internal.Handshaker.Endpoint value) {
-        if (localEndpointBuilder_ == null) {
-          if (localEndpoint_ != null) {
-            localEndpoint_ =
-              io.grpc.alts.internal.Handshaker.Endpoint.newBuilder(localEndpoint_).mergeFrom(value).buildPartial();
-          } else {
-            localEndpoint_ = value;
-          }
-          onChanged();
-        } else {
-          localEndpointBuilder_.mergeFrom(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Local endpoint information of the connection to the client,
-       * such as local IP address, port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
-       */
-      public Builder clearLocalEndpoint() {
-        if (localEndpointBuilder_ == null) {
-          localEndpoint_ = null;
-          onChanged();
-        } else {
-          localEndpoint_ = null;
-          localEndpointBuilder_ = null;
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * (Optional) Local endpoint information of the connection to the client,
-       * such as local IP address, port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.Endpoint.Builder getLocalEndpointBuilder() {
-        
-        onChanged();
-        return getLocalEndpointFieldBuilder().getBuilder();
-      }
-      /**
-       * <pre>
-       * (Optional) Local endpoint information of the connection to the client,
-       * such as local IP address, port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.EndpointOrBuilder getLocalEndpointOrBuilder() {
-        if (localEndpointBuilder_ != null) {
-          return localEndpointBuilder_.getMessageOrBuilder();
-        } else {
-          return localEndpoint_ == null ?
-              io.grpc.alts.internal.Handshaker.Endpoint.getDefaultInstance() : localEndpoint_;
-        }
-      }
-      /**
-       * <pre>
-       * (Optional) Local endpoint information of the connection to the client,
-       * such as local IP address, port number, and network protocol.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
-       */
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.Handshaker.Endpoint, io.grpc.alts.internal.Handshaker.Endpoint.Builder, io.grpc.alts.internal.Handshaker.EndpointOrBuilder> 
-          getLocalEndpointFieldBuilder() {
-        if (localEndpointBuilder_ == null) {
-          localEndpointBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
-              io.grpc.alts.internal.Handshaker.Endpoint, io.grpc.alts.internal.Handshaker.Endpoint.Builder, io.grpc.alts.internal.Handshaker.EndpointOrBuilder>(
-                  getLocalEndpoint(),
-                  getParentForChildren(),
-                  isClean());
-          localEndpoint_ = null;
-        }
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-      /**
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-       * <pre>
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-       *
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-      public Builder setServerStart(io.grpc.alts.internal.Handshaker.StartServerHandshakeReq value) {
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-       * <pre>
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-       * <pre>
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-       * </pre>
-       *
-       * <code>.grpc.gcp.StartServerHandshakeReq server_start = 2;</code>
-       */
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-       * <pre>
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-       * </pre>
-       *
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-      }
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-       * <pre>
-       * The start server handshake request message.
-       * </pre>
-       *
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-       * <pre>
-       * The start server handshake request message.
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-       *
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-       */
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-      /**
-       * <pre>
-       * The next handshake request message.
-       * </pre>
-       *
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-        return reqOneofCase_ == 3;
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-      /**
-       * <pre>
-       * The next handshake request message.
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-       *
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-      /**
-       * <pre>
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-       * </pre>
-       *
-       * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
-       */
-      public Builder setNext(io.grpc.alts.internal.Handshaker.NextHandshakeMessageReq value) {
-        if (nextBuilder_ == null) {
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-          onChanged();
-        } else {
-          nextBuilder_.setMessage(value);
-        }
-        reqOneofCase_ = 3;
-        return this;
-      }
-      /**
-       * <pre>
-       * The next handshake request message.
-       * </pre>
-       *
-       * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
-       */
-      public Builder setNext(
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-          nextBuilder_.setMessage(builderForValue.build());
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-        reqOneofCase_ = 3;
-        return this;
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-      /**
-       * <pre>
-       * The next handshake request message.
-       * </pre>
-       *
-       * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
-       */
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-        if (nextBuilder_ == null) {
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-        return this;
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-      /**
-       * <pre>
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-       * </pre>
-       *
-       * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
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-        return this;
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-      /**
-       * <pre>
-       * The next handshake request message.
-       * </pre>
-       *
-       * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.NextHandshakeMessageReq.Builder getNextBuilder() {
-        return getNextFieldBuilder().getBuilder();
-      }
-      /**
-       * <pre>
-       * The next handshake request message.
-       * </pre>
-       *
-       * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
-       */
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-      /**
-       * <pre>
-       * The next handshake request message.
-       * </pre>
-       *
-       * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
-       */
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-
-
-      // @@protoc_insertion_point(builder_scope:grpc.gcp.HandshakerReq)
-    }
-
-    // @@protoc_insertion_point(class_scope:grpc.gcp.HandshakerReq)
-    private static final io.grpc.alts.internal.Handshaker.HandshakerReq DEFAULT_INSTANCE;
-    static {
-      DEFAULT_INSTANCE = new io.grpc.alts.internal.Handshaker.HandshakerReq();
-    }
-
-    public static io.grpc.alts.internal.Handshaker.HandshakerReq getDefaultInstance() {
-      return DEFAULT_INSTANCE;
-    }
-
-    private static final com.google.protobuf.Parser<HandshakerReq>
-        PARSER = new com.google.protobuf.AbstractParser<HandshakerReq>() {
-      public HandshakerReq parsePartialFrom(
-          com.google.protobuf.CodedInputStream input,
-          com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-          throws com.google.protobuf.InvalidProtocolBufferException {
-        return new HandshakerReq(input, extensionRegistry);
-      }
-    };
-
-    public static com.google.protobuf.Parser<HandshakerReq> parser() {
-      return PARSER;
-    }
-
-    @java.lang.Override
-    public com.google.protobuf.Parser<HandshakerReq> getParserForType() {
-      return PARSER;
-    }
-
-    public io.grpc.alts.internal.Handshaker.HandshakerReq getDefaultInstanceForType() {
-      return DEFAULT_INSTANCE;
-    }
-
-  }
-
-  public interface HandshakerResultOrBuilder extends
-      // @@protoc_insertion_point(interface_extends:grpc.gcp.HandshakerResult)
-      com.google.protobuf.MessageOrBuilder {
-
-    /**
-     * <pre>
-     * The application protocol negotiated for this connection.
-     * </pre>
-     *
-     * <code>string application_protocol = 1;</code>
-     */
-    java.lang.String getApplicationProtocol();
-    /**
-     * <pre>
-     * The application protocol negotiated for this connection.
-     * </pre>
-     *
-     * <code>string application_protocol = 1;</code>
-     */
-    com.google.protobuf.ByteString
-        getApplicationProtocolBytes();
-
-    /**
-     * <pre>
-     * The record protocol negotiated for this connection.
-     * </pre>
-     *
-     * <code>string record_protocol = 2;</code>
-     */
-    java.lang.String getRecordProtocol();
-    /**
-     * <pre>
-     * The record protocol negotiated for this connection.
-     * </pre>
-     *
-     * <code>string record_protocol = 2;</code>
-     */
-    com.google.protobuf.ByteString
-        getRecordProtocolBytes();
-
-    /**
-     * <pre>
-     * Cryptographic key data. The key data may be more than the key length
-     * required for the record protocol, thus the client of the handshaker
-     * service needs to truncate the key data into the right key length.
-     * </pre>
-     *
-     * <code>bytes key_data = 3;</code>
-     */
-    com.google.protobuf.ByteString getKeyData();
-
-    /**
-     * <pre>
-     * The authenticated identity of the peer.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Identity peer_identity = 4;</code>
-     */
-    boolean hasPeerIdentity();
-    /**
-     * <pre>
-     * The authenticated identity of the peer.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Identity peer_identity = 4;</code>
-     */
-    io.grpc.alts.internal.Handshaker.Identity getPeerIdentity();
-    /**
-     * <pre>
-     * The authenticated identity of the peer.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Identity peer_identity = 4;</code>
-     */
-    io.grpc.alts.internal.Handshaker.IdentityOrBuilder getPeerIdentityOrBuilder();
-
-    /**
-     * <pre>
-     * The local identity used in the handshake.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Identity local_identity = 5;</code>
-     */
-    boolean hasLocalIdentity();
-    /**
-     * <pre>
-     * The local identity used in the handshake.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Identity local_identity = 5;</code>
-     */
-    io.grpc.alts.internal.Handshaker.Identity getLocalIdentity();
-    /**
-     * <pre>
-     * The local identity used in the handshake.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Identity local_identity = 5;</code>
-     */
-    io.grpc.alts.internal.Handshaker.IdentityOrBuilder getLocalIdentityOrBuilder();
-
-    /**
-     * <pre>
-     * Indicate whether the handshaker service client should keep the channel
-     * between the handshaker service open, e.g., in order to handle
-     * post-handshake messages in the future.
-     * </pre>
-     *
-     * <code>bool keep_channel_open = 6;</code>
-     */
-    boolean getKeepChannelOpen();
-
-    /**
-     * <pre>
-     * The RPC protocol versions supported by the peer.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
-     */
-    boolean hasPeerRpcVersions();
-    /**
-     * <pre>
-     * The RPC protocol versions supported by the peer.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
-     */
-    io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions getPeerRpcVersions();
-    /**
-     * <pre>
-     * The RPC protocol versions supported by the peer.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
-     */
-    io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersionsOrBuilder getPeerRpcVersionsOrBuilder();
-  }
-  /**
-   * Protobuf type {@code grpc.gcp.HandshakerResult}
-   */
-  public  static final class HandshakerResult extends
-      com.google.protobuf.GeneratedMessageV3 implements
-      // @@protoc_insertion_point(message_implements:grpc.gcp.HandshakerResult)
-      HandshakerResultOrBuilder {
-  private static final long serialVersionUID = 0L;
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-
-              applicationProtocol_ = s;
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-
-              recordProtocol_ = s;
-              break;
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-            case 26: {
-
-              keyData_ = input.readBytes();
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-              io.grpc.alts.internal.Handshaker.Identity.Builder subBuilder = null;
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-    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
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-    public static final int APPLICATION_PROTOCOL_FIELD_NUMBER = 1;
-    private volatile java.lang.Object applicationProtocol_;
-    /**
-     * <pre>
-     * The application protocol negotiated for this connection.
-     * </pre>
-     *
-     * <code>string application_protocol = 1;</code>
-     */
-    public java.lang.String getApplicationProtocol() {
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-     * </pre>
-     *
-     * <code>string application_protocol = 1;</code>
-     */
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-        com.google.protobuf.ByteString b = 
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-        applicationProtocol_ = b;
-        return b;
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-
-    public static final int RECORD_PROTOCOL_FIELD_NUMBER = 2;
-    private volatile java.lang.Object recordProtocol_;
-    /**
-     * <pre>
-     * The record protocol negotiated for this connection.
-     * </pre>
-     *
-     * <code>string record_protocol = 2;</code>
-     */
-    public java.lang.String getRecordProtocol() {
-      java.lang.Object ref = recordProtocol_;
-      if (ref instanceof java.lang.String) {
-        return (java.lang.String) ref;
-      } else {
-        com.google.protobuf.ByteString bs = 
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-        java.lang.String s = bs.toStringUtf8();
-        recordProtocol_ = s;
-        return s;
-      }
-    }
-    /**
-     * <pre>
-     * The record protocol negotiated for this connection.
-     * </pre>
-     *
-     * <code>string record_protocol = 2;</code>
-     */
-    public com.google.protobuf.ByteString
-        getRecordProtocolBytes() {
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-        recordProtocol_ = b;
-        return b;
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-    public static final int KEY_DATA_FIELD_NUMBER = 3;
-    private com.google.protobuf.ByteString keyData_;
-    /**
-     * <pre>
-     * Cryptographic key data. The key data may be more than the key length
-     * required for the record protocol, thus the client of the handshaker
-     * service needs to truncate the key data into the right key length.
-     * </pre>
-     *
-     * <code>bytes key_data = 3;</code>
-     */
-    public com.google.protobuf.ByteString getKeyData() {
-      return keyData_;
-    }
-
-    public static final int PEER_IDENTITY_FIELD_NUMBER = 4;
-    private io.grpc.alts.internal.Handshaker.Identity peerIdentity_;
-    /**
-     * <pre>
-     * The authenticated identity of the peer.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Identity peer_identity = 4;</code>
-     */
-    public boolean hasPeerIdentity() {
-      return peerIdentity_ != null;
-    }
-    /**
-     * <pre>
-     * The authenticated identity of the peer.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Identity peer_identity = 4;</code>
-     */
-    public io.grpc.alts.internal.Handshaker.Identity getPeerIdentity() {
-      return peerIdentity_ == null ? io.grpc.alts.internal.Handshaker.Identity.getDefaultInstance() : peerIdentity_;
-    }
-    /**
-     * <pre>
-     * The authenticated identity of the peer.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Identity peer_identity = 4;</code>
-     */
-    public io.grpc.alts.internal.Handshaker.IdentityOrBuilder getPeerIdentityOrBuilder() {
-      return getPeerIdentity();
-    }
-
-    public static final int LOCAL_IDENTITY_FIELD_NUMBER = 5;
-    private io.grpc.alts.internal.Handshaker.Identity localIdentity_;
-    /**
-     * <pre>
-     * The local identity used in the handshake.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Identity local_identity = 5;</code>
-     */
-    public boolean hasLocalIdentity() {
-      return localIdentity_ != null;
-    }
-    /**
-     * <pre>
-     * The local identity used in the handshake.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Identity local_identity = 5;</code>
-     */
-    public io.grpc.alts.internal.Handshaker.Identity getLocalIdentity() {
-      return localIdentity_ == null ? io.grpc.alts.internal.Handshaker.Identity.getDefaultInstance() : localIdentity_;
-    }
-    /**
-     * <pre>
-     * The local identity used in the handshake.
-     * </pre>
-     *
-     * <code>.grpc.gcp.Identity local_identity = 5;</code>
-     */
-    public io.grpc.alts.internal.Handshaker.IdentityOrBuilder getLocalIdentityOrBuilder() {
-      return getLocalIdentity();
-    }
-
-    public static final int KEEP_CHANNEL_OPEN_FIELD_NUMBER = 6;
-    private boolean keepChannelOpen_;
-    /**
-     * <pre>
-     * Indicate whether the handshaker service client should keep the channel
-     * between the handshaker service open, e.g., in order to handle
-     * post-handshake messages in the future.
-     * </pre>
-     *
-     * <code>bool keep_channel_open = 6;</code>
-     */
-    public boolean getKeepChannelOpen() {
-      return keepChannelOpen_;
-    }
-
-    public static final int PEER_RPC_VERSIONS_FIELD_NUMBER = 7;
-    private io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions peerRpcVersions_;
-    /**
-     * <pre>
-     * The RPC protocol versions supported by the peer.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
-     */
-    public boolean hasPeerRpcVersions() {
-      return peerRpcVersions_ != null;
-    }
-    /**
-     * <pre>
-     * The RPC protocol versions supported by the peer.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
-     */
-    public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions getPeerRpcVersions() {
-      return peerRpcVersions_ == null ? io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.getDefaultInstance() : peerRpcVersions_;
-    }
-    /**
-     * <pre>
-     * The RPC protocol versions supported by the peer.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
-     */
-    public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersionsOrBuilder getPeerRpcVersionsOrBuilder() {
-      return getPeerRpcVersions();
-    }
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-    private byte memoizedIsInitialized = -1;
-    public final boolean isInitialized() {
-      byte isInitialized = memoizedIsInitialized;
-      if (isInitialized == 1) return true;
-      if (isInitialized == 0) return false;
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-      memoizedIsInitialized = 1;
-      return true;
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-    public void writeTo(com.google.protobuf.CodedOutputStream output)
-                        throws java.io.IOException {
-      if (!getApplicationProtocolBytes().isEmpty()) {
-        com.google.protobuf.GeneratedMessageV3.writeString(output, 1, applicationProtocol_);
-      }
-      if (!getRecordProtocolBytes().isEmpty()) {
-        com.google.protobuf.GeneratedMessageV3.writeString(output, 2, recordProtocol_);
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-            peerIdentity_ =
-              io.grpc.alts.internal.Handshaker.Identity.newBuilder(peerIdentity_).mergeFrom(value).buildPartial();
-          } else {
-            peerIdentity_ = value;
-          }
-          onChanged();
-        } else {
-          peerIdentityBuilder_.mergeFrom(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * The authenticated identity of the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity peer_identity = 4;</code>
-       */
-      public Builder clearPeerIdentity() {
-        if (peerIdentityBuilder_ == null) {
-          peerIdentity_ = null;
-          onChanged();
-        } else {
-          peerIdentity_ = null;
-          peerIdentityBuilder_ = null;
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * The authenticated identity of the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity peer_identity = 4;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.Identity.Builder getPeerIdentityBuilder() {
-        
-        onChanged();
-        return getPeerIdentityFieldBuilder().getBuilder();
-      }
-      /**
-       * <pre>
-       * The authenticated identity of the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity peer_identity = 4;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.IdentityOrBuilder getPeerIdentityOrBuilder() {
-        if (peerIdentityBuilder_ != null) {
-          return peerIdentityBuilder_.getMessageOrBuilder();
-        } else {
-          return peerIdentity_ == null ?
-              io.grpc.alts.internal.Handshaker.Identity.getDefaultInstance() : peerIdentity_;
-        }
-      }
-      /**
-       * <pre>
-       * The authenticated identity of the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity peer_identity = 4;</code>
-       */
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.Handshaker.Identity, io.grpc.alts.internal.Handshaker.Identity.Builder, io.grpc.alts.internal.Handshaker.IdentityOrBuilder> 
-          getPeerIdentityFieldBuilder() {
-        if (peerIdentityBuilder_ == null) {
-          peerIdentityBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
-              io.grpc.alts.internal.Handshaker.Identity, io.grpc.alts.internal.Handshaker.Identity.Builder, io.grpc.alts.internal.Handshaker.IdentityOrBuilder>(
-                  getPeerIdentity(),
-                  getParentForChildren(),
-                  isClean());
-          peerIdentity_ = null;
-        }
-        return peerIdentityBuilder_;
-      }
-
-      private io.grpc.alts.internal.Handshaker.Identity localIdentity_ = null;
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.Handshaker.Identity, io.grpc.alts.internal.Handshaker.Identity.Builder, io.grpc.alts.internal.Handshaker.IdentityOrBuilder> localIdentityBuilder_;
-      /**
-       * <pre>
-       * The local identity used in the handshake.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity local_identity = 5;</code>
-       */
-      public boolean hasLocalIdentity() {
-        return localIdentityBuilder_ != null || localIdentity_ != null;
-      }
-      /**
-       * <pre>
-       * The local identity used in the handshake.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity local_identity = 5;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.Identity getLocalIdentity() {
-        if (localIdentityBuilder_ == null) {
-          return localIdentity_ == null ? io.grpc.alts.internal.Handshaker.Identity.getDefaultInstance() : localIdentity_;
-        } else {
-          return localIdentityBuilder_.getMessage();
-        }
-      }
-      /**
-       * <pre>
-       * The local identity used in the handshake.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity local_identity = 5;</code>
-       */
-      public Builder setLocalIdentity(io.grpc.alts.internal.Handshaker.Identity value) {
-        if (localIdentityBuilder_ == null) {
-          if (value == null) {
-            throw new NullPointerException();
-          }
-          localIdentity_ = value;
-          onChanged();
-        } else {
-          localIdentityBuilder_.setMessage(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * The local identity used in the handshake.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity local_identity = 5;</code>
-       */
-      public Builder setLocalIdentity(
-          io.grpc.alts.internal.Handshaker.Identity.Builder builderForValue) {
-        if (localIdentityBuilder_ == null) {
-          localIdentity_ = builderForValue.build();
-          onChanged();
-        } else {
-          localIdentityBuilder_.setMessage(builderForValue.build());
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * The local identity used in the handshake.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity local_identity = 5;</code>
-       */
-      public Builder mergeLocalIdentity(io.grpc.alts.internal.Handshaker.Identity value) {
-        if (localIdentityBuilder_ == null) {
-          if (localIdentity_ != null) {
-            localIdentity_ =
-              io.grpc.alts.internal.Handshaker.Identity.newBuilder(localIdentity_).mergeFrom(value).buildPartial();
-          } else {
-            localIdentity_ = value;
-          }
-          onChanged();
-        } else {
-          localIdentityBuilder_.mergeFrom(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * The local identity used in the handshake.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity local_identity = 5;</code>
-       */
-      public Builder clearLocalIdentity() {
-        if (localIdentityBuilder_ == null) {
-          localIdentity_ = null;
-          onChanged();
-        } else {
-          localIdentity_ = null;
-          localIdentityBuilder_ = null;
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * The local identity used in the handshake.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity local_identity = 5;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.Identity.Builder getLocalIdentityBuilder() {
-        
-        onChanged();
-        return getLocalIdentityFieldBuilder().getBuilder();
-      }
-      /**
-       * <pre>
-       * The local identity used in the handshake.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity local_identity = 5;</code>
-       */
-      public io.grpc.alts.internal.Handshaker.IdentityOrBuilder getLocalIdentityOrBuilder() {
-        if (localIdentityBuilder_ != null) {
-          return localIdentityBuilder_.getMessageOrBuilder();
-        } else {
-          return localIdentity_ == null ?
-              io.grpc.alts.internal.Handshaker.Identity.getDefaultInstance() : localIdentity_;
-        }
-      }
-      /**
-       * <pre>
-       * The local identity used in the handshake.
-       * </pre>
-       *
-       * <code>.grpc.gcp.Identity local_identity = 5;</code>
-       */
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.Handshaker.Identity, io.grpc.alts.internal.Handshaker.Identity.Builder, io.grpc.alts.internal.Handshaker.IdentityOrBuilder> 
-          getLocalIdentityFieldBuilder() {
-        if (localIdentityBuilder_ == null) {
-          localIdentityBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
-              io.grpc.alts.internal.Handshaker.Identity, io.grpc.alts.internal.Handshaker.Identity.Builder, io.grpc.alts.internal.Handshaker.IdentityOrBuilder>(
-                  getLocalIdentity(),
-                  getParentForChildren(),
-                  isClean());
-          localIdentity_ = null;
-        }
-        return localIdentityBuilder_;
-      }
-
-      private boolean keepChannelOpen_ ;
-      /**
-       * <pre>
-       * Indicate whether the handshaker service client should keep the channel
-       * between the handshaker service open, e.g., in order to handle
-       * post-handshake messages in the future.
-       * </pre>
-       *
-       * <code>bool keep_channel_open = 6;</code>
-       */
-      public boolean getKeepChannelOpen() {
-        return keepChannelOpen_;
-      }
-      /**
-       * <pre>
-       * Indicate whether the handshaker service client should keep the channel
-       * between the handshaker service open, e.g., in order to handle
-       * post-handshake messages in the future.
-       * </pre>
-       *
-       * <code>bool keep_channel_open = 6;</code>
-       */
-      public Builder setKeepChannelOpen(boolean value) {
-        
-        keepChannelOpen_ = value;
-        onChanged();
-        return this;
-      }
-      /**
-       * <pre>
-       * Indicate whether the handshaker service client should keep the channel
-       * between the handshaker service open, e.g., in order to handle
-       * post-handshake messages in the future.
-       * </pre>
-       *
-       * <code>bool keep_channel_open = 6;</code>
-       */
-      public Builder clearKeepChannelOpen() {
-        
-        keepChannelOpen_ = false;
-        onChanged();
-        return this;
-      }
-
-      private io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions peerRpcVersions_ = null;
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Builder, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersionsOrBuilder> peerRpcVersionsBuilder_;
-      /**
-       * <pre>
-       * The RPC protocol versions supported by the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
-       */
-      public boolean hasPeerRpcVersions() {
-        return peerRpcVersionsBuilder_ != null || peerRpcVersions_ != null;
-      }
-      /**
-       * <pre>
-       * The RPC protocol versions supported by the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
-       */
-      public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions getPeerRpcVersions() {
-        if (peerRpcVersionsBuilder_ == null) {
-          return peerRpcVersions_ == null ? io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.getDefaultInstance() : peerRpcVersions_;
-        } else {
-          return peerRpcVersionsBuilder_.getMessage();
-        }
-      }
-      /**
-       * <pre>
-       * The RPC protocol versions supported by the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
-       */
-      public Builder setPeerRpcVersions(io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions value) {
-        if (peerRpcVersionsBuilder_ == null) {
-          if (value == null) {
-            throw new NullPointerException();
-          }
-          peerRpcVersions_ = value;
-          onChanged();
-        } else {
-          peerRpcVersionsBuilder_.setMessage(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * The RPC protocol versions supported by the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
-       */
-      public Builder setPeerRpcVersions(
-          io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Builder builderForValue) {
-        if (peerRpcVersionsBuilder_ == null) {
-          peerRpcVersions_ = builderForValue.build();
-          onChanged();
-        } else {
-          peerRpcVersionsBuilder_.setMessage(builderForValue.build());
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * The RPC protocol versions supported by the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
-       */
-      public Builder mergePeerRpcVersions(io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions value) {
-        if (peerRpcVersionsBuilder_ == null) {
-          if (peerRpcVersions_ != null) {
-            peerRpcVersions_ =
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.newBuilder(peerRpcVersions_).mergeFrom(value).buildPartial();
-          } else {
-            peerRpcVersions_ = value;
-          }
-          onChanged();
-        } else {
-          peerRpcVersionsBuilder_.mergeFrom(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * The RPC protocol versions supported by the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
-       */
-      public Builder clearPeerRpcVersions() {
-        if (peerRpcVersionsBuilder_ == null) {
-          peerRpcVersions_ = null;
-          onChanged();
-        } else {
-          peerRpcVersions_ = null;
-          peerRpcVersionsBuilder_ = null;
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * The RPC protocol versions supported by the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
-       */
-      public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Builder getPeerRpcVersionsBuilder() {
-        
-        onChanged();
-        return getPeerRpcVersionsFieldBuilder().getBuilder();
-      }
-      /**
-       * <pre>
-       * The RPC protocol versions supported by the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
-       */
-      public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersionsOrBuilder getPeerRpcVersionsOrBuilder() {
-        if (peerRpcVersionsBuilder_ != null) {
-          return peerRpcVersionsBuilder_.getMessageOrBuilder();
-        } else {
-          return peerRpcVersions_ == null ?
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.getDefaultInstance() : peerRpcVersions_;
-        }
-      }
-      /**
-       * <pre>
-       * The RPC protocol versions supported by the peer.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
-       */
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Builder, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersionsOrBuilder> 
-          getPeerRpcVersionsFieldBuilder() {
-        if (peerRpcVersionsBuilder_ == null) {
-          peerRpcVersionsBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
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-                  getParentForChildren(),
-                  isClean());
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-        return peerRpcVersionsBuilder_;
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-
-      public final Builder mergeUnknownFields(
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-        return super.mergeUnknownFields(unknownFields);
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-
-
-      // @@protoc_insertion_point(builder_scope:grpc.gcp.HandshakerResult)
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-
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-    private static final io.grpc.alts.internal.Handshaker.HandshakerResult DEFAULT_INSTANCE;
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-      DEFAULT_INSTANCE = new io.grpc.alts.internal.Handshaker.HandshakerResult();
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-          com.google.protobuf.CodedInputStream input,
-          com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-          throws com.google.protobuf.InvalidProtocolBufferException {
-        return new HandshakerResult(input, extensionRegistry);
-      }
-    };
-
-    public static com.google.protobuf.Parser<HandshakerResult> parser() {
-      return PARSER;
-    }
-
-    @java.lang.Override
-    public com.google.protobuf.Parser<HandshakerResult> getParserForType() {
-      return PARSER;
-    }
-
-    public io.grpc.alts.internal.Handshaker.HandshakerResult getDefaultInstanceForType() {
-      return DEFAULT_INSTANCE;
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-
-  }
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-      // @@protoc_insertion_point(interface_extends:grpc.gcp.HandshakerStatus)
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-
-    /**
-     * <pre>
-     * The status code. This could be the gRPC status code.
-     * </pre>
-     *
-     * <code>uint32 code = 1;</code>
-     */
-    int getCode();
-
-    /**
-     * <pre>
-     * The status details.
-     * </pre>
-     *
-     * <code>string details = 2;</code>
-     */
-    java.lang.String getDetails();
-    /**
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-     * The status details.
-     * </pre>
-     *
-     * <code>string details = 2;</code>
-     */
-    com.google.protobuf.ByteString
-        getDetailsBytes();
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-  /**
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-   */
-  public  static final class HandshakerStatus extends
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-
-        return this;
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-      /**
-       * <pre>
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-        
-        onChanged();
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-      return DEFAULT_INSTANCE;
-    }
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-        PARSER = new com.google.protobuf.AbstractParser<HandshakerResp>() {
-      public HandshakerResp parsePartialFrom(
-          com.google.protobuf.CodedInputStream input,
-          com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-          throws com.google.protobuf.InvalidProtocolBufferException {
-        return new HandshakerResp(input, extensionRegistry);
-      }
-    };
-
-    public static com.google.protobuf.Parser<HandshakerResp> parser() {
-      return PARSER;
-    }
-
-    @java.lang.Override
-    public com.google.protobuf.Parser<HandshakerResp> getParserForType() {
-      return PARSER;
-    }
-
-    public io.grpc.alts.internal.Handshaker.HandshakerResp getDefaultInstanceForType() {
-      return DEFAULT_INSTANCE;
-    }
-
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-      "rpc/gcp/transport_security_common.proto\"" +
-      "Y\n\010Endpoint\022\022\n\nip_address\030\001 \001(\t\022\014\n\004port\030" +
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-      "StartClientHandshakeReq\022@\n\033handshake_sec" +
-      "urity_protocol\030\001 \001(\0162\033.grpc.gcp.Handshak" +
-      "eProtocol\022\035\n\025application_protocols\030\002 \003(\t" +
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-      "olVersions\032_\n\030HandshakeParametersEntry\022\013" +
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-      "rverHandshakeParameters:\0028\001\"+\n\027NextHands" +
-      "hakeMessageReq\022\020\n\010in_bytes\030\001 \001(\014\"\305\001\n\rHan" +
-      "dshakerReq\0229\n\014client_start\030\001 \001(\0132!.grpc." +
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-      "ndshakeMessageReqH\000B\013\n\treq_oneof\"\207\002\n\020Han" +
-      "dshakerResult\022\034\n\024application_protocol\030\001 " +
-      "\001(\t\022\027\n\017record_protocol\030\002 \001(\t\022\020\n\010key_data" +
-      "\030\003 \001(\014\022)\n\rpeer_identity\030\004 \001(\0132\022.grpc.gcp" +
-      ".Identity\022*\n\016local_identity\030\005 \001(\0132\022.grpc" +
-      ".gcp.Identity\022\031\n\021keep_channel_open\030\006 \001(\010" +
-      "\0228\n\021peer_rpc_versions\030\007 \001(\0132\035.grpc.gcp.R" +
-      "pcProtocolVersions\"1\n\020HandshakerStatus\022\014" +
-      "\n\004code\030\001 \001(\r\022\017\n\007details\030\002 \001(\t\"\224\001\n\016Handsh" +
-      "akerResp\022\022\n\nout_frames\030\001 \001(\014\022\026\n\016bytes_co" +
-      "nsumed\030\002 \001(\r\022*\n\006result\030\003 \001(\0132\032.grpc.gcp." +
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-      "gcp.HandshakerStatus*J\n\021HandshakeProtoco" +
-      "l\022\"\n\036HANDSHAKE_PROTOCOL_UNSPECIFIED\020\000\022\007\n" +
-      "\003TLS\020\001\022\010\n\004ALTS\020\002*E\n\017NetworkProtocol\022 \n\034N" +
-      "ETWORK_PROTOCOL_UNSPECIFIED\020\000\022\007\n\003TCP\020\001\022\007" +
-      "\n\003UDP\020\0022[\n\021HandshakerService\022F\n\013DoHandsh" +
-      "ake\022\027.grpc.gcp.HandshakerReq\032\030.grpc.gcp." +
-      "HandshakerResp\"\000(\0010\001B\027\n\025io.grpc.alts.int" +
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-  // @@protoc_insertion_point(outer_class_scope)
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diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerProto.java b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerProto.java
new file mode 100644
index 0000000000..60ffa51a73
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerProto.java
@@ -0,0 +1,235 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+public final class HandshakerProto {
+  private HandshakerProto() {}
+  public static void registerAllExtensions(
+      com.google.protobuf.ExtensionRegistryLite registry) {
+  }
+
+  public static void registerAllExtensions(
+      com.google.protobuf.ExtensionRegistry registry) {
+    registerAllExtensions(
+        (com.google.protobuf.ExtensionRegistryLite) registry);
+  }
+  static final com.google.protobuf.Descriptors.Descriptor
+    internal_static_grpc_gcp_Endpoint_descriptor;
+  static final 
+    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internal_static_grpc_gcp_Endpoint_fieldAccessorTable;
+  static final com.google.protobuf.Descriptors.Descriptor
+    internal_static_grpc_gcp_Identity_descriptor;
+  static final 
+    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internal_static_grpc_gcp_Identity_fieldAccessorTable;
+  static final com.google.protobuf.Descriptors.Descriptor
+    internal_static_grpc_gcp_Identity_AttributesEntry_descriptor;
+  static final 
+    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internal_static_grpc_gcp_Identity_AttributesEntry_fieldAccessorTable;
+  static final com.google.protobuf.Descriptors.Descriptor
+    internal_static_grpc_gcp_StartClientHandshakeReq_descriptor;
+  static final 
+    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internal_static_grpc_gcp_StartClientHandshakeReq_fieldAccessorTable;
+  static final com.google.protobuf.Descriptors.Descriptor
+    internal_static_grpc_gcp_ServerHandshakeParameters_descriptor;
+  static final 
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+      internal_static_grpc_gcp_ServerHandshakeParameters_fieldAccessorTable;
+  static final com.google.protobuf.Descriptors.Descriptor
+    internal_static_grpc_gcp_StartServerHandshakeReq_descriptor;
+  static final 
+    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internal_static_grpc_gcp_StartServerHandshakeReq_fieldAccessorTable;
+  static final com.google.protobuf.Descriptors.Descriptor
+    internal_static_grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_descriptor;
+  static final 
+    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internal_static_grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_fieldAccessorTable;
+  static final com.google.protobuf.Descriptors.Descriptor
+    internal_static_grpc_gcp_NextHandshakeMessageReq_descriptor;
+  static final 
+    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internal_static_grpc_gcp_NextHandshakeMessageReq_fieldAccessorTable;
+  static final com.google.protobuf.Descriptors.Descriptor
+    internal_static_grpc_gcp_HandshakerReq_descriptor;
+  static final 
+    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internal_static_grpc_gcp_HandshakerReq_fieldAccessorTable;
+  static final com.google.protobuf.Descriptors.Descriptor
+    internal_static_grpc_gcp_HandshakerResult_descriptor;
+  static final 
+    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internal_static_grpc_gcp_HandshakerResult_fieldAccessorTable;
+  static final com.google.protobuf.Descriptors.Descriptor
+    internal_static_grpc_gcp_HandshakerStatus_descriptor;
+  static final 
+    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internal_static_grpc_gcp_HandshakerStatus_fieldAccessorTable;
+  static final com.google.protobuf.Descriptors.Descriptor
+    internal_static_grpc_gcp_HandshakerResp_descriptor;
+  static final 
+    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internal_static_grpc_gcp_HandshakerResp_fieldAccessorTable;
+
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+      getDescriptor() {
+    return descriptor;
+  }
+  private static  com.google.protobuf.Descriptors.FileDescriptor
+      descriptor;
+  static {
+    java.lang.String[] descriptorData = {
+      "\n\031grpc/gcp/handshaker.proto\022\010grpc.gcp\032(g" +
+      "rpc/gcp/transport_security_common.proto\"" +
+      "Y\n\010Endpoint\022\022\n\nip_address\030\001 \001(\t\022\014\n\004port\030" +
+      "\002 \001(\005\022+\n\010protocol\030\003 \001(\0162\031.grpc.gcp.Netwo" +
+      "rkProtocol\"\266\001\n\010Identity\022\031\n\017service_accou" +
+      "nt\030\001 \001(\tH\000\022\022\n\010hostname\030\002 \001(\tH\000\0226\n\nattrib" +
+      "utes\030\003 \003(\0132\".grpc.gcp.Identity.Attribute" +
+      "sEntry\0321\n\017AttributesEntry\022\013\n\003key\030\001 \001(\t\022\r" +
+      "\n\005value\030\002 \001(\t:\0028\001B\020\n\016identity_oneof\"\222\003\n\027" +
+      "StartClientHandshakeReq\022@\n\033handshake_sec" +
+      "urity_protocol\030\001 \001(\0162\033.grpc.gcp.Handshak" +
+      "eProtocol\022\035\n\025application_protocols\030\002 \003(\t" +
+      "\022\030\n\020record_protocols\030\003 \003(\t\022-\n\021target_ide" +
+      "ntities\030\004 \003(\0132\022.grpc.gcp.Identity\022*\n\016loc" +
+      "al_identity\030\005 \001(\0132\022.grpc.gcp.Identity\022*\n" +
+      "\016local_endpoint\030\006 \001(\0132\022.grpc.gcp.Endpoin" +
+      "t\022+\n\017remote_endpoint\030\007 \001(\0132\022.grpc.gcp.En" +
+      "dpoint\022\023\n\013target_name\030\010 \001(\t\0223\n\014rpc_versi" +
+      "ons\030\t \001(\0132\035.grpc.gcp.RpcProtocolVersions" +
+      "\"c\n\031ServerHandshakeParameters\022\030\n\020record_" +
+      "protocols\030\001 \003(\t\022,\n\020local_identities\030\002 \003(" +
+      "\0132\022.grpc.gcp.Identity\"\223\003\n\027StartServerHan" +
+      "dshakeReq\022\035\n\025application_protocols\030\001 \003(\t" +
+      "\022X\n\024handshake_parameters\030\002 \003(\0132:.grpc.gc" +
+      "p.StartServerHandshakeReq.HandshakeParam" +
+      "etersEntry\022\020\n\010in_bytes\030\003 \001(\014\022*\n\016local_en" +
+      "dpoint\030\004 \001(\0132\022.grpc.gcp.Endpoint\022+\n\017remo" +
+      "te_endpoint\030\005 \001(\0132\022.grpc.gcp.Endpoint\0223\n" +
+      "\014rpc_versions\030\006 \001(\0132\035.grpc.gcp.RpcProtoc" +
+      "olVersions\032_\n\030HandshakeParametersEntry\022\013" +
+      "\n\003key\030\001 \001(\005\0222\n\005value\030\002 \001(\0132#.grpc.gcp.Se" +
+      "rverHandshakeParameters:\0028\001\"+\n\027NextHands" +
+      "hakeMessageReq\022\020\n\010in_bytes\030\001 \001(\014\"\305\001\n\rHan" +
+      "dshakerReq\0229\n\014client_start\030\001 \001(\0132!.grpc." +
+      "gcp.StartClientHandshakeReqH\000\0229\n\014server_" +
+      "start\030\002 \001(\0132!.grpc.gcp.StartServerHandsh" +
+      "akeReqH\000\0221\n\004next\030\003 \001(\0132!.grpc.gcp.NextHa" +
+      "ndshakeMessageReqH\000B\013\n\treq_oneof\"\207\002\n\020Han" +
+      "dshakerResult\022\034\n\024application_protocol\030\001 " +
+      "\001(\t\022\027\n\017record_protocol\030\002 \001(\t\022\020\n\010key_data" +
+      "\030\003 \001(\014\022)\n\rpeer_identity\030\004 \001(\0132\022.grpc.gcp" +
+      ".Identity\022*\n\016local_identity\030\005 \001(\0132\022.grpc" +
+      ".gcp.Identity\022\031\n\021keep_channel_open\030\006 \001(\010" +
+      "\0228\n\021peer_rpc_versions\030\007 \001(\0132\035.grpc.gcp.R" +
+      "pcProtocolVersions\"1\n\020HandshakerStatus\022\014" +
+      "\n\004code\030\001 \001(\r\022\017\n\007details\030\002 \001(\t\"\224\001\n\016Handsh" +
+      "akerResp\022\022\n\nout_frames\030\001 \001(\014\022\026\n\016bytes_co" +
+      "nsumed\030\002 \001(\r\022*\n\006result\030\003 \001(\0132\032.grpc.gcp." +
+      "HandshakerResult\022*\n\006status\030\004 \001(\0132\032.grpc." +
+      "gcp.HandshakerStatus*J\n\021HandshakeProtoco" +
+      "l\022\"\n\036HANDSHAKE_PROTOCOL_UNSPECIFIED\020\000\022\007\n" +
+      "\003TLS\020\001\022\010\n\004ALTS\020\002*E\n\017NetworkProtocol\022 \n\034N" +
+      "ETWORK_PROTOCOL_UNSPECIFIED\020\000\022\007\n\003TCP\020\001\022\007" +
+      "\n\003UDP\020\0022[\n\021HandshakerService\022F\n\013DoHandsh" +
+      "ake\022\027.grpc.gcp.HandshakerReq\032\030.grpc.gcp." +
+      "HandshakerResp\"\000(\0010\001Bk\n\025io.grpc.alts.int" +
+      "ernalB\017HandshakerProtoP\001Z?google.golang." +
+      "org/grpc/credentials/alts/internal/proto" +
+      "/grpc_gcpb\006proto3"
+    };
+    com.google.protobuf.Descriptors.FileDescriptor.InternalDescriptorAssigner assigner =
+        new com.google.protobuf.Descriptors.FileDescriptor.    InternalDescriptorAssigner() {
+          public com.google.protobuf.ExtensionRegistry assignDescriptors(
+              com.google.protobuf.Descriptors.FileDescriptor root) {
+            descriptor = root;
+            return null;
+          }
+        };
+    com.google.protobuf.Descriptors.FileDescriptor
+      .internalBuildGeneratedFileFrom(descriptorData,
+        new com.google.protobuf.Descriptors.FileDescriptor[] {
+          io.grpc.alts.internal.TransportSecurityCommonProto.getDescriptor(),
+        }, assigner);
+    internal_static_grpc_gcp_Endpoint_descriptor =
+      getDescriptor().getMessageTypes().get(0);
+    internal_static_grpc_gcp_Endpoint_fieldAccessorTable = new
+      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
+        internal_static_grpc_gcp_Endpoint_descriptor,
+        new java.lang.String[] { "IpAddress", "Port", "Protocol", });
+    internal_static_grpc_gcp_Identity_descriptor =
+      getDescriptor().getMessageTypes().get(1);
+    internal_static_grpc_gcp_Identity_fieldAccessorTable = new
+      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
+        internal_static_grpc_gcp_Identity_descriptor,
+        new java.lang.String[] { "ServiceAccount", "Hostname", "Attributes", "IdentityOneof", });
+    internal_static_grpc_gcp_Identity_AttributesEntry_descriptor =
+      internal_static_grpc_gcp_Identity_descriptor.getNestedTypes().get(0);
+    internal_static_grpc_gcp_Identity_AttributesEntry_fieldAccessorTable = new
+      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
+        internal_static_grpc_gcp_Identity_AttributesEntry_descriptor,
+        new java.lang.String[] { "Key", "Value", });
+    internal_static_grpc_gcp_StartClientHandshakeReq_descriptor =
+      getDescriptor().getMessageTypes().get(2);
+    internal_static_grpc_gcp_StartClientHandshakeReq_fieldAccessorTable = new
+      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
+        internal_static_grpc_gcp_StartClientHandshakeReq_descriptor,
+        new java.lang.String[] { "HandshakeSecurityProtocol", "ApplicationProtocols", "RecordProtocols", "TargetIdentities", "LocalIdentity", "LocalEndpoint", "RemoteEndpoint", "TargetName", "RpcVersions", });
+    internal_static_grpc_gcp_ServerHandshakeParameters_descriptor =
+      getDescriptor().getMessageTypes().get(3);
+    internal_static_grpc_gcp_ServerHandshakeParameters_fieldAccessorTable = new
+      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
+        internal_static_grpc_gcp_ServerHandshakeParameters_descriptor,
+        new java.lang.String[] { "RecordProtocols", "LocalIdentities", });
+    internal_static_grpc_gcp_StartServerHandshakeReq_descriptor =
+      getDescriptor().getMessageTypes().get(4);
+    internal_static_grpc_gcp_StartServerHandshakeReq_fieldAccessorTable = new
+      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
+        internal_static_grpc_gcp_StartServerHandshakeReq_descriptor,
+        new java.lang.String[] { "ApplicationProtocols", "HandshakeParameters", "InBytes", "LocalEndpoint", "RemoteEndpoint", "RpcVersions", });
+    internal_static_grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_descriptor =
+      internal_static_grpc_gcp_StartServerHandshakeReq_descriptor.getNestedTypes().get(0);
+    internal_static_grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_fieldAccessorTable = new
+      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
+        internal_static_grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_descriptor,
+        new java.lang.String[] { "Key", "Value", });
+    internal_static_grpc_gcp_NextHandshakeMessageReq_descriptor =
+      getDescriptor().getMessageTypes().get(5);
+    internal_static_grpc_gcp_NextHandshakeMessageReq_fieldAccessorTable = new
+      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
+        internal_static_grpc_gcp_NextHandshakeMessageReq_descriptor,
+        new java.lang.String[] { "InBytes", });
+    internal_static_grpc_gcp_HandshakerReq_descriptor =
+      getDescriptor().getMessageTypes().get(6);
+    internal_static_grpc_gcp_HandshakerReq_fieldAccessorTable = new
+      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
+        internal_static_grpc_gcp_HandshakerReq_descriptor,
+        new java.lang.String[] { "ClientStart", "ServerStart", "Next", "ReqOneof", });
+    internal_static_grpc_gcp_HandshakerResult_descriptor =
+      getDescriptor().getMessageTypes().get(7);
+    internal_static_grpc_gcp_HandshakerResult_fieldAccessorTable = new
+      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
+        internal_static_grpc_gcp_HandshakerResult_descriptor,
+        new java.lang.String[] { "ApplicationProtocol", "RecordProtocol", "KeyData", "PeerIdentity", "LocalIdentity", "KeepChannelOpen", "PeerRpcVersions", });
+    internal_static_grpc_gcp_HandshakerStatus_descriptor =
+      getDescriptor().getMessageTypes().get(8);
+    internal_static_grpc_gcp_HandshakerStatus_fieldAccessorTable = new
+      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
+        internal_static_grpc_gcp_HandshakerStatus_descriptor,
+        new java.lang.String[] { "Code", "Details", });
+    internal_static_grpc_gcp_HandshakerResp_descriptor =
+      getDescriptor().getMessageTypes().get(9);
+    internal_static_grpc_gcp_HandshakerResp_fieldAccessorTable = new
+      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
+        internal_static_grpc_gcp_HandshakerResp_descriptor,
+        new java.lang.String[] { "OutFrames", "BytesConsumed", "Result", "Status", });
+    io.grpc.alts.internal.TransportSecurityCommonProto.getDescriptor();
+  }
+
+  // @@protoc_insertion_point(outer_class_scope)
+}
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerReq.java b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerReq.java
new file mode 100644
index 0000000000..57ab28351d
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerReq.java
@@ -0,0 +1,1213 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+/**
+ * Protobuf type {@code grpc.gcp.HandshakerReq}
+ */
+public  final class HandshakerReq extends
+    com.google.protobuf.GeneratedMessageV3 implements
+    // @@protoc_insertion_point(message_implements:grpc.gcp.HandshakerReq)
+    HandshakerReqOrBuilder {
+private static final long serialVersionUID = 0L;
+  // Use HandshakerReq.newBuilder() to construct.
+  private HandshakerReq(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
+    super(builder);
+  }
+  private HandshakerReq() {
+  }
+
+  @java.lang.Override
+  public final com.google.protobuf.UnknownFieldSet
+  getUnknownFields() {
+    return this.unknownFields;
+  }
+  private HandshakerReq(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    this();
+    if (extensionRegistry == null) {
+      throw new java.lang.NullPointerException();
+    }
+    int mutable_bitField0_ = 0;
+    com.google.protobuf.UnknownFieldSet.Builder unknownFields =
+        com.google.protobuf.UnknownFieldSet.newBuilder();
+    try {
+      boolean done = false;
+      while (!done) {
+        int tag = input.readTag();
+        switch (tag) {
+          case 0:
+            done = true;
+            break;
+          default: {
+            if (!parseUnknownFieldProto3(
+                input, unknownFields, extensionRegistry, tag)) {
+              done = true;
+            }
+            break;
+          }
+          case 10: {
+            io.grpc.alts.internal.StartClientHandshakeReq.Builder subBuilder = null;
+            if (reqOneofCase_ == 1) {
+              subBuilder = ((io.grpc.alts.internal.StartClientHandshakeReq) reqOneof_).toBuilder();
+            }
+            reqOneof_ =
+                input.readMessage(io.grpc.alts.internal.StartClientHandshakeReq.parser(), extensionRegistry);
+            if (subBuilder != null) {
+              subBuilder.mergeFrom((io.grpc.alts.internal.StartClientHandshakeReq) reqOneof_);
+              reqOneof_ = subBuilder.buildPartial();
+            }
+            reqOneofCase_ = 1;
+            break;
+          }
+          case 18: {
+            io.grpc.alts.internal.StartServerHandshakeReq.Builder subBuilder = null;
+            if (reqOneofCase_ == 2) {
+              subBuilder = ((io.grpc.alts.internal.StartServerHandshakeReq) reqOneof_).toBuilder();
+            }
+            reqOneof_ =
+                input.readMessage(io.grpc.alts.internal.StartServerHandshakeReq.parser(), extensionRegistry);
+            if (subBuilder != null) {
+              subBuilder.mergeFrom((io.grpc.alts.internal.StartServerHandshakeReq) reqOneof_);
+              reqOneof_ = subBuilder.buildPartial();
+            }
+            reqOneofCase_ = 2;
+            break;
+          }
+          case 26: {
+            io.grpc.alts.internal.NextHandshakeMessageReq.Builder subBuilder = null;
+            if (reqOneofCase_ == 3) {
+              subBuilder = ((io.grpc.alts.internal.NextHandshakeMessageReq) reqOneof_).toBuilder();
+            }
+            reqOneof_ =
+                input.readMessage(io.grpc.alts.internal.NextHandshakeMessageReq.parser(), extensionRegistry);
+            if (subBuilder != null) {
+              subBuilder.mergeFrom((io.grpc.alts.internal.NextHandshakeMessageReq) reqOneof_);
+              reqOneof_ = subBuilder.buildPartial();
+            }
+            reqOneofCase_ = 3;
+            break;
+          }
+        }
+      }
+    } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+      throw e.setUnfinishedMessage(this);
+    } catch (java.io.IOException e) {
+      throw new com.google.protobuf.InvalidProtocolBufferException(
+          e).setUnfinishedMessage(this);
+    } finally {
+      this.unknownFields = unknownFields.build();
+      makeExtensionsImmutable();
+    }
+  }
+  public static final com.google.protobuf.Descriptors.Descriptor
+      getDescriptor() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerReq_descriptor;
+  }
+
+  protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internalGetFieldAccessorTable() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerReq_fieldAccessorTable
+        .ensureFieldAccessorsInitialized(
+            io.grpc.alts.internal.HandshakerReq.class, io.grpc.alts.internal.HandshakerReq.Builder.class);
+  }
+
+  private int reqOneofCase_ = 0;
+  private java.lang.Object reqOneof_;
+  public enum ReqOneofCase
+      implements com.google.protobuf.Internal.EnumLite {
+    CLIENT_START(1),
+    SERVER_START(2),
+    NEXT(3),
+    REQONEOF_NOT_SET(0);
+    private final int value;
+    private ReqOneofCase(int value) {
+      this.value = value;
+    }
+    /**
+     * @deprecated Use {@link #forNumber(int)} instead.
+     */
+    @java.lang.Deprecated
+    public static ReqOneofCase valueOf(int value) {
+      return forNumber(value);
+    }
+
+    public static ReqOneofCase forNumber(int value) {
+      switch (value) {
+        case 1: return CLIENT_START;
+        case 2: return SERVER_START;
+        case 3: return NEXT;
+        case 0: return REQONEOF_NOT_SET;
+        default: return null;
+      }
+    }
+    public int getNumber() {
+      return this.value;
+    }
+  };
+
+  public ReqOneofCase
+  getReqOneofCase() {
+    return ReqOneofCase.forNumber(
+        reqOneofCase_);
+  }
+
+  public static final int CLIENT_START_FIELD_NUMBER = 1;
+  /**
+   * <pre>
+   * The start client handshake request message.
+   * </pre>
+   *
+   * <code>.grpc.gcp.StartClientHandshakeReq client_start = 1;</code>
+   */
+  public boolean hasClientStart() {
+    return reqOneofCase_ == 1;
+  }
+  /**
+   * <pre>
+   * The start client handshake request message.
+   * </pre>
+   *
+   * <code>.grpc.gcp.StartClientHandshakeReq client_start = 1;</code>
+   */
+  public io.grpc.alts.internal.StartClientHandshakeReq getClientStart() {
+    if (reqOneofCase_ == 1) {
+       return (io.grpc.alts.internal.StartClientHandshakeReq) reqOneof_;
+    }
+    return io.grpc.alts.internal.StartClientHandshakeReq.getDefaultInstance();
+  }
+  /**
+   * <pre>
+   * The start client handshake request message.
+   * </pre>
+   *
+   * <code>.grpc.gcp.StartClientHandshakeReq client_start = 1;</code>
+   */
+  public io.grpc.alts.internal.StartClientHandshakeReqOrBuilder getClientStartOrBuilder() {
+    if (reqOneofCase_ == 1) {
+       return (io.grpc.alts.internal.StartClientHandshakeReq) reqOneof_;
+    }
+    return io.grpc.alts.internal.StartClientHandshakeReq.getDefaultInstance();
+  }
+
+  public static final int SERVER_START_FIELD_NUMBER = 2;
+  /**
+   * <pre>
+   * The start server handshake request message.
+   * </pre>
+   *
+   * <code>.grpc.gcp.StartServerHandshakeReq server_start = 2;</code>
+   */
+  public boolean hasServerStart() {
+    return reqOneofCase_ == 2;
+  }
+  /**
+   * <pre>
+   * The start server handshake request message.
+   * </pre>
+   *
+   * <code>.grpc.gcp.StartServerHandshakeReq server_start = 2;</code>
+   */
+  public io.grpc.alts.internal.StartServerHandshakeReq getServerStart() {
+    if (reqOneofCase_ == 2) {
+       return (io.grpc.alts.internal.StartServerHandshakeReq) reqOneof_;
+    }
+    return io.grpc.alts.internal.StartServerHandshakeReq.getDefaultInstance();
+  }
+  /**
+   * <pre>
+   * The start server handshake request message.
+   * </pre>
+   *
+   * <code>.grpc.gcp.StartServerHandshakeReq server_start = 2;</code>
+   */
+  public io.grpc.alts.internal.StartServerHandshakeReqOrBuilder getServerStartOrBuilder() {
+    if (reqOneofCase_ == 2) {
+       return (io.grpc.alts.internal.StartServerHandshakeReq) reqOneof_;
+    }
+    return io.grpc.alts.internal.StartServerHandshakeReq.getDefaultInstance();
+  }
+
+  public static final int NEXT_FIELD_NUMBER = 3;
+  /**
+   * <pre>
+   * The next handshake request message.
+   * </pre>
+   *
+   * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
+   */
+  public boolean hasNext() {
+    return reqOneofCase_ == 3;
+  }
+  /**
+   * <pre>
+   * The next handshake request message.
+   * </pre>
+   *
+   * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
+   */
+  public io.grpc.alts.internal.NextHandshakeMessageReq getNext() {
+    if (reqOneofCase_ == 3) {
+       return (io.grpc.alts.internal.NextHandshakeMessageReq) reqOneof_;
+    }
+    return io.grpc.alts.internal.NextHandshakeMessageReq.getDefaultInstance();
+  }
+  /**
+   * <pre>
+   * The next handshake request message.
+   * </pre>
+   *
+   * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
+   */
+  public io.grpc.alts.internal.NextHandshakeMessageReqOrBuilder getNextOrBuilder() {
+    if (reqOneofCase_ == 3) {
+       return (io.grpc.alts.internal.NextHandshakeMessageReq) reqOneof_;
+    }
+    return io.grpc.alts.internal.NextHandshakeMessageReq.getDefaultInstance();
+  }
+
+  private byte memoizedIsInitialized = -1;
+  public final boolean isInitialized() {
+    byte isInitialized = memoizedIsInitialized;
+    if (isInitialized == 1) return true;
+    if (isInitialized == 0) return false;
+
+    memoizedIsInitialized = 1;
+    return true;
+  }
+
+  public void writeTo(com.google.protobuf.CodedOutputStream output)
+                      throws java.io.IOException {
+    if (reqOneofCase_ == 1) {
+      output.writeMessage(1, (io.grpc.alts.internal.StartClientHandshakeReq) reqOneof_);
+    }
+    if (reqOneofCase_ == 2) {
+      output.writeMessage(2, (io.grpc.alts.internal.StartServerHandshakeReq) reqOneof_);
+    }
+    if (reqOneofCase_ == 3) {
+      output.writeMessage(3, (io.grpc.alts.internal.NextHandshakeMessageReq) reqOneof_);
+    }
+    unknownFields.writeTo(output);
+  }
+
+  public int getSerializedSize() {
+    int size = memoizedSize;
+    if (size != -1) return size;
+
+    size = 0;
+    if (reqOneofCase_ == 1) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeMessageSize(1, (io.grpc.alts.internal.StartClientHandshakeReq) reqOneof_);
+    }
+    if (reqOneofCase_ == 2) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeMessageSize(2, (io.grpc.alts.internal.StartServerHandshakeReq) reqOneof_);
+    }
+    if (reqOneofCase_ == 3) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeMessageSize(3, (io.grpc.alts.internal.NextHandshakeMessageReq) reqOneof_);
+    }
+    size += unknownFields.getSerializedSize();
+    memoizedSize = size;
+    return size;
+  }
+
+  @java.lang.Override
+  public boolean equals(final java.lang.Object obj) {
+    if (obj == this) {
+     return true;
+    }
+    if (!(obj instanceof io.grpc.alts.internal.HandshakerReq)) {
+      return super.equals(obj);
+    }
+    io.grpc.alts.internal.HandshakerReq other = (io.grpc.alts.internal.HandshakerReq) obj;
+
+    boolean result = true;
+    result = result && getReqOneofCase().equals(
+        other.getReqOneofCase());
+    if (!result) return false;
+    switch (reqOneofCase_) {
+      case 1:
+        result = result && getClientStart()
+            .equals(other.getClientStart());
+        break;
+      case 2:
+        result = result && getServerStart()
+            .equals(other.getServerStart());
+        break;
+      case 3:
+        result = result && getNext()
+            .equals(other.getNext());
+        break;
+      case 0:
+      default:
+    }
+    result = result && unknownFields.equals(other.unknownFields);
+    return result;
+  }
+
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+  public int hashCode() {
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+    }
+    int hash = 41;
+    hash = (19 * hash) + getDescriptor().hashCode();
+    switch (reqOneofCase_) {
+      case 1:
+        hash = (37 * hash) + CLIENT_START_FIELD_NUMBER;
+        hash = (53 * hash) + getClientStart().hashCode();
+        break;
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+        hash = (37 * hash) + SERVER_START_FIELD_NUMBER;
+        hash = (53 * hash) + getServerStart().hashCode();
+        break;
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+        hash = (37 * hash) + NEXT_FIELD_NUMBER;
+        hash = (53 * hash) + getNext().hashCode();
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+      default:
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+    hash = (29 * hash) + unknownFields.hashCode();
+    memoizedHashCode = hash;
+    return hash;
+  }
+
+  public static io.grpc.alts.internal.HandshakerReq parseFrom(
+      java.nio.ByteBuffer data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.HandshakerReq parseFrom(
+      java.nio.ByteBuffer data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerReq parseFrom(
+      com.google.protobuf.ByteString data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.HandshakerReq parseFrom(
+      com.google.protobuf.ByteString data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerReq parseFrom(byte[] data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.HandshakerReq parseFrom(
+      byte[] data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerReq parseFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.HandshakerReq parseFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerReq parseDelimitedFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.HandshakerReq parseDelimitedFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerReq parseFrom(
+      com.google.protobuf.CodedInputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.HandshakerReq parseFrom(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+
+  public Builder newBuilderForType() { return newBuilder(); }
+  public static Builder newBuilder() {
+    return DEFAULT_INSTANCE.toBuilder();
+  }
+  public static Builder newBuilder(io.grpc.alts.internal.HandshakerReq prototype) {
+    return DEFAULT_INSTANCE.toBuilder().mergeFrom(prototype);
+  }
+  public Builder toBuilder() {
+    return this == DEFAULT_INSTANCE
+        ? new Builder() : new Builder().mergeFrom(this);
+  }
+
+  @java.lang.Override
+  protected Builder newBuilderForType(
+      com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+    Builder builder = new Builder(parent);
+    return builder;
+  }
+  /**
+   * Protobuf type {@code grpc.gcp.HandshakerReq}
+   */
+  public static final class Builder extends
+      com.google.protobuf.GeneratedMessageV3.Builder<Builder> implements
+      // @@protoc_insertion_point(builder_implements:grpc.gcp.HandshakerReq)
+      io.grpc.alts.internal.HandshakerReqOrBuilder {
+    public static final com.google.protobuf.Descriptors.Descriptor
+        getDescriptor() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerReq_descriptor;
+    }
+
+    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+        internalGetFieldAccessorTable() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerReq_fieldAccessorTable
+          .ensureFieldAccessorsInitialized(
+              io.grpc.alts.internal.HandshakerReq.class, io.grpc.alts.internal.HandshakerReq.Builder.class);
+    }
+
+    // Construct using io.grpc.alts.internal.HandshakerReq.newBuilder()
+    private Builder() {
+      maybeForceBuilderInitialization();
+    }
+
+    private Builder(
+        com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+      super(parent);
+      maybeForceBuilderInitialization();
+    }
+    private void maybeForceBuilderInitialization() {
+      if (com.google.protobuf.GeneratedMessageV3
+              .alwaysUseFieldBuilders) {
+      }
+    }
+    public Builder clear() {
+      super.clear();
+      reqOneofCase_ = 0;
+      reqOneof_ = null;
+      return this;
+    }
+
+    public com.google.protobuf.Descriptors.Descriptor
+        getDescriptorForType() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerReq_descriptor;
+    }
+
+    public io.grpc.alts.internal.HandshakerReq getDefaultInstanceForType() {
+      return io.grpc.alts.internal.HandshakerReq.getDefaultInstance();
+    }
+
+    public io.grpc.alts.internal.HandshakerReq build() {
+      io.grpc.alts.internal.HandshakerReq result = buildPartial();
+      if (!result.isInitialized()) {
+        throw newUninitializedMessageException(result);
+      }
+      return result;
+    }
+
+    public io.grpc.alts.internal.HandshakerReq buildPartial() {
+      io.grpc.alts.internal.HandshakerReq result = new io.grpc.alts.internal.HandshakerReq(this);
+      if (reqOneofCase_ == 1) {
+        if (clientStartBuilder_ == null) {
+          result.reqOneof_ = reqOneof_;
+        } else {
+          result.reqOneof_ = clientStartBuilder_.build();
+        }
+      }
+      if (reqOneofCase_ == 2) {
+        if (serverStartBuilder_ == null) {
+          result.reqOneof_ = reqOneof_;
+        } else {
+          result.reqOneof_ = serverStartBuilder_.build();
+        }
+      }
+      if (reqOneofCase_ == 3) {
+        if (nextBuilder_ == null) {
+          result.reqOneof_ = reqOneof_;
+        } else {
+          result.reqOneof_ = nextBuilder_.build();
+        }
+      }
+      result.reqOneofCase_ = reqOneofCase_;
+      onBuilt();
+      return result;
+    }
+
+    public Builder clone() {
+      return (Builder) super.clone();
+    }
+    public Builder setField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.setField(field, value);
+    }
+    public Builder clearField(
+        com.google.protobuf.Descriptors.FieldDescriptor field) {
+      return (Builder) super.clearField(field);
+    }
+    public Builder clearOneof(
+        com.google.protobuf.Descriptors.OneofDescriptor oneof) {
+      return (Builder) super.clearOneof(oneof);
+    }
+    public Builder setRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        int index, java.lang.Object value) {
+      return (Builder) super.setRepeatedField(field, index, value);
+    }
+    public Builder addRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.addRepeatedField(field, value);
+    }
+    public Builder mergeFrom(com.google.protobuf.Message other) {
+      if (other instanceof io.grpc.alts.internal.HandshakerReq) {
+        return mergeFrom((io.grpc.alts.internal.HandshakerReq)other);
+      } else {
+        super.mergeFrom(other);
+        return this;
+      }
+    }
+
+    public Builder mergeFrom(io.grpc.alts.internal.HandshakerReq other) {
+      if (other == io.grpc.alts.internal.HandshakerReq.getDefaultInstance()) return this;
+      switch (other.getReqOneofCase()) {
+        case CLIENT_START: {
+          mergeClientStart(other.getClientStart());
+          break;
+        }
+        case SERVER_START: {
+          mergeServerStart(other.getServerStart());
+          break;
+        }
+        case NEXT: {
+          mergeNext(other.getNext());
+          break;
+        }
+        case REQONEOF_NOT_SET: {
+          break;
+        }
+      }
+      this.mergeUnknownFields(other.unknownFields);
+      onChanged();
+      return this;
+    }
+
+    public final boolean isInitialized() {
+      return true;
+    }
+
+    public Builder mergeFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      io.grpc.alts.internal.HandshakerReq parsedMessage = null;
+      try {
+        parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);
+      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+        parsedMessage = (io.grpc.alts.internal.HandshakerReq) e.getUnfinishedMessage();
+        throw e.unwrapIOException();
+      } finally {
+        if (parsedMessage != null) {
+          mergeFrom(parsedMessage);
+        }
+      }
+      return this;
+    }
+    private int reqOneofCase_ = 0;
+    private java.lang.Object reqOneof_;
+    public ReqOneofCase
+        getReqOneofCase() {
+      return ReqOneofCase.forNumber(
+          reqOneofCase_);
+    }
+
+    public Builder clearReqOneof() {
+      reqOneofCase_ = 0;
+      reqOneof_ = null;
+      onChanged();
+      return this;
+    }
+
+
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.StartClientHandshakeReq, io.grpc.alts.internal.StartClientHandshakeReq.Builder, io.grpc.alts.internal.StartClientHandshakeReqOrBuilder> clientStartBuilder_;
+    /**
+     * <pre>
+     * The start client handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.StartClientHandshakeReq client_start = 1;</code>
+     */
+    public boolean hasClientStart() {
+      return reqOneofCase_ == 1;
+    }
+    /**
+     * <pre>
+     * The start client handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.StartClientHandshakeReq client_start = 1;</code>
+     */
+    public io.grpc.alts.internal.StartClientHandshakeReq getClientStart() {
+      if (clientStartBuilder_ == null) {
+        if (reqOneofCase_ == 1) {
+          return (io.grpc.alts.internal.StartClientHandshakeReq) reqOneof_;
+        }
+        return io.grpc.alts.internal.StartClientHandshakeReq.getDefaultInstance();
+      } else {
+        if (reqOneofCase_ == 1) {
+          return clientStartBuilder_.getMessage();
+        }
+        return io.grpc.alts.internal.StartClientHandshakeReq.getDefaultInstance();
+      }
+    }
+    /**
+     * <pre>
+     * The start client handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.StartClientHandshakeReq client_start = 1;</code>
+     */
+    public Builder setClientStart(io.grpc.alts.internal.StartClientHandshakeReq value) {
+      if (clientStartBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        reqOneof_ = value;
+        onChanged();
+      } else {
+        clientStartBuilder_.setMessage(value);
+      }
+      reqOneofCase_ = 1;
+      return this;
+    }
+    /**
+     * <pre>
+     * The start client handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.StartClientHandshakeReq client_start = 1;</code>
+     */
+    public Builder setClientStart(
+        io.grpc.alts.internal.StartClientHandshakeReq.Builder builderForValue) {
+      if (clientStartBuilder_ == null) {
+        reqOneof_ = builderForValue.build();
+        onChanged();
+      } else {
+        clientStartBuilder_.setMessage(builderForValue.build());
+      }
+      reqOneofCase_ = 1;
+      return this;
+    }
+    /**
+     * <pre>
+     * The start client handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.StartClientHandshakeReq client_start = 1;</code>
+     */
+    public Builder mergeClientStart(io.grpc.alts.internal.StartClientHandshakeReq value) {
+      if (clientStartBuilder_ == null) {
+        if (reqOneofCase_ == 1 &&
+            reqOneof_ != io.grpc.alts.internal.StartClientHandshakeReq.getDefaultInstance()) {
+          reqOneof_ = io.grpc.alts.internal.StartClientHandshakeReq.newBuilder((io.grpc.alts.internal.StartClientHandshakeReq) reqOneof_)
+              .mergeFrom(value).buildPartial();
+        } else {
+          reqOneof_ = value;
+        }
+        onChanged();
+      } else {
+        if (reqOneofCase_ == 1) {
+          clientStartBuilder_.mergeFrom(value);
+        }
+        clientStartBuilder_.setMessage(value);
+      }
+      reqOneofCase_ = 1;
+      return this;
+    }
+    /**
+     * <pre>
+     * The start client handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.StartClientHandshakeReq client_start = 1;</code>
+     */
+    public Builder clearClientStart() {
+      if (clientStartBuilder_ == null) {
+        if (reqOneofCase_ == 1) {
+          reqOneofCase_ = 0;
+          reqOneof_ = null;
+          onChanged();
+        }
+      } else {
+        if (reqOneofCase_ == 1) {
+          reqOneofCase_ = 0;
+          reqOneof_ = null;
+        }
+        clientStartBuilder_.clear();
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * The start client handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.StartClientHandshakeReq client_start = 1;</code>
+     */
+    public io.grpc.alts.internal.StartClientHandshakeReq.Builder getClientStartBuilder() {
+      return getClientStartFieldBuilder().getBuilder();
+    }
+    /**
+     * <pre>
+     * The start client handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.StartClientHandshakeReq client_start = 1;</code>
+     */
+    public io.grpc.alts.internal.StartClientHandshakeReqOrBuilder getClientStartOrBuilder() {
+      if ((reqOneofCase_ == 1) && (clientStartBuilder_ != null)) {
+        return clientStartBuilder_.getMessageOrBuilder();
+      } else {
+        if (reqOneofCase_ == 1) {
+          return (io.grpc.alts.internal.StartClientHandshakeReq) reqOneof_;
+        }
+        return io.grpc.alts.internal.StartClientHandshakeReq.getDefaultInstance();
+      }
+    }
+    /**
+     * <pre>
+     * The start client handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.StartClientHandshakeReq client_start = 1;</code>
+     */
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.StartClientHandshakeReq, io.grpc.alts.internal.StartClientHandshakeReq.Builder, io.grpc.alts.internal.StartClientHandshakeReqOrBuilder> 
+        getClientStartFieldBuilder() {
+      if (clientStartBuilder_ == null) {
+        if (!(reqOneofCase_ == 1)) {
+          reqOneof_ = io.grpc.alts.internal.StartClientHandshakeReq.getDefaultInstance();
+        }
+        clientStartBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
+            io.grpc.alts.internal.StartClientHandshakeReq, io.grpc.alts.internal.StartClientHandshakeReq.Builder, io.grpc.alts.internal.StartClientHandshakeReqOrBuilder>(
+                (io.grpc.alts.internal.StartClientHandshakeReq) reqOneof_,
+                getParentForChildren(),
+                isClean());
+        reqOneof_ = null;
+      }
+      reqOneofCase_ = 1;
+      onChanged();;
+      return clientStartBuilder_;
+    }
+
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.StartServerHandshakeReq, io.grpc.alts.internal.StartServerHandshakeReq.Builder, io.grpc.alts.internal.StartServerHandshakeReqOrBuilder> serverStartBuilder_;
+    /**
+     * <pre>
+     * The start server handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.StartServerHandshakeReq server_start = 2;</code>
+     */
+    public boolean hasServerStart() {
+      return reqOneofCase_ == 2;
+    }
+    /**
+     * <pre>
+     * The start server handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.StartServerHandshakeReq server_start = 2;</code>
+     */
+    public io.grpc.alts.internal.StartServerHandshakeReq getServerStart() {
+      if (serverStartBuilder_ == null) {
+        if (reqOneofCase_ == 2) {
+          return (io.grpc.alts.internal.StartServerHandshakeReq) reqOneof_;
+        }
+        return io.grpc.alts.internal.StartServerHandshakeReq.getDefaultInstance();
+      } else {
+        if (reqOneofCase_ == 2) {
+          return serverStartBuilder_.getMessage();
+        }
+        return io.grpc.alts.internal.StartServerHandshakeReq.getDefaultInstance();
+      }
+    }
+    /**
+     * <pre>
+     * The start server handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.StartServerHandshakeReq server_start = 2;</code>
+     */
+    public Builder setServerStart(io.grpc.alts.internal.StartServerHandshakeReq value) {
+      if (serverStartBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        reqOneof_ = value;
+        onChanged();
+      } else {
+        serverStartBuilder_.setMessage(value);
+      }
+      reqOneofCase_ = 2;
+      return this;
+    }
+    /**
+     * <pre>
+     * The start server handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.StartServerHandshakeReq server_start = 2;</code>
+     */
+    public Builder setServerStart(
+        io.grpc.alts.internal.StartServerHandshakeReq.Builder builderForValue) {
+      if (serverStartBuilder_ == null) {
+        reqOneof_ = builderForValue.build();
+        onChanged();
+      } else {
+        serverStartBuilder_.setMessage(builderForValue.build());
+      }
+      reqOneofCase_ = 2;
+      return this;
+    }
+    /**
+     * <pre>
+     * The start server handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.StartServerHandshakeReq server_start = 2;</code>
+     */
+    public Builder mergeServerStart(io.grpc.alts.internal.StartServerHandshakeReq value) {
+      if (serverStartBuilder_ == null) {
+        if (reqOneofCase_ == 2 &&
+            reqOneof_ != io.grpc.alts.internal.StartServerHandshakeReq.getDefaultInstance()) {
+          reqOneof_ = io.grpc.alts.internal.StartServerHandshakeReq.newBuilder((io.grpc.alts.internal.StartServerHandshakeReq) reqOneof_)
+              .mergeFrom(value).buildPartial();
+        } else {
+          reqOneof_ = value;
+        }
+        onChanged();
+      } else {
+        if (reqOneofCase_ == 2) {
+          serverStartBuilder_.mergeFrom(value);
+        }
+        serverStartBuilder_.setMessage(value);
+      }
+      reqOneofCase_ = 2;
+      return this;
+    }
+    /**
+     * <pre>
+     * The start server handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.StartServerHandshakeReq server_start = 2;</code>
+     */
+    public Builder clearServerStart() {
+      if (serverStartBuilder_ == null) {
+        if (reqOneofCase_ == 2) {
+          reqOneofCase_ = 0;
+          reqOneof_ = null;
+          onChanged();
+        }
+      } else {
+        if (reqOneofCase_ == 2) {
+          reqOneofCase_ = 0;
+          reqOneof_ = null;
+        }
+        serverStartBuilder_.clear();
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * The start server handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.StartServerHandshakeReq server_start = 2;</code>
+     */
+    public io.grpc.alts.internal.StartServerHandshakeReq.Builder getServerStartBuilder() {
+      return getServerStartFieldBuilder().getBuilder();
+    }
+    /**
+     * <pre>
+     * The start server handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.StartServerHandshakeReq server_start = 2;</code>
+     */
+    public io.grpc.alts.internal.StartServerHandshakeReqOrBuilder getServerStartOrBuilder() {
+      if ((reqOneofCase_ == 2) && (serverStartBuilder_ != null)) {
+        return serverStartBuilder_.getMessageOrBuilder();
+      } else {
+        if (reqOneofCase_ == 2) {
+          return (io.grpc.alts.internal.StartServerHandshakeReq) reqOneof_;
+        }
+        return io.grpc.alts.internal.StartServerHandshakeReq.getDefaultInstance();
+      }
+    }
+    /**
+     * <pre>
+     * The start server handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.StartServerHandshakeReq server_start = 2;</code>
+     */
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.StartServerHandshakeReq, io.grpc.alts.internal.StartServerHandshakeReq.Builder, io.grpc.alts.internal.StartServerHandshakeReqOrBuilder> 
+        getServerStartFieldBuilder() {
+      if (serverStartBuilder_ == null) {
+        if (!(reqOneofCase_ == 2)) {
+          reqOneof_ = io.grpc.alts.internal.StartServerHandshakeReq.getDefaultInstance();
+        }
+        serverStartBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
+            io.grpc.alts.internal.StartServerHandshakeReq, io.grpc.alts.internal.StartServerHandshakeReq.Builder, io.grpc.alts.internal.StartServerHandshakeReqOrBuilder>(
+                (io.grpc.alts.internal.StartServerHandshakeReq) reqOneof_,
+                getParentForChildren(),
+                isClean());
+        reqOneof_ = null;
+      }
+      reqOneofCase_ = 2;
+      onChanged();;
+      return serverStartBuilder_;
+    }
+
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.NextHandshakeMessageReq, io.grpc.alts.internal.NextHandshakeMessageReq.Builder, io.grpc.alts.internal.NextHandshakeMessageReqOrBuilder> nextBuilder_;
+    /**
+     * <pre>
+     * The next handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
+     */
+    public boolean hasNext() {
+      return reqOneofCase_ == 3;
+    }
+    /**
+     * <pre>
+     * The next handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
+     */
+    public io.grpc.alts.internal.NextHandshakeMessageReq getNext() {
+      if (nextBuilder_ == null) {
+        if (reqOneofCase_ == 3) {
+          return (io.grpc.alts.internal.NextHandshakeMessageReq) reqOneof_;
+        }
+        return io.grpc.alts.internal.NextHandshakeMessageReq.getDefaultInstance();
+      } else {
+        if (reqOneofCase_ == 3) {
+          return nextBuilder_.getMessage();
+        }
+        return io.grpc.alts.internal.NextHandshakeMessageReq.getDefaultInstance();
+      }
+    }
+    /**
+     * <pre>
+     * The next handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
+     */
+    public Builder setNext(io.grpc.alts.internal.NextHandshakeMessageReq value) {
+      if (nextBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        reqOneof_ = value;
+        onChanged();
+      } else {
+        nextBuilder_.setMessage(value);
+      }
+      reqOneofCase_ = 3;
+      return this;
+    }
+    /**
+     * <pre>
+     * The next handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
+     */
+    public Builder setNext(
+        io.grpc.alts.internal.NextHandshakeMessageReq.Builder builderForValue) {
+      if (nextBuilder_ == null) {
+        reqOneof_ = builderForValue.build();
+        onChanged();
+      } else {
+        nextBuilder_.setMessage(builderForValue.build());
+      }
+      reqOneofCase_ = 3;
+      return this;
+    }
+    /**
+     * <pre>
+     * The next handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
+     */
+    public Builder mergeNext(io.grpc.alts.internal.NextHandshakeMessageReq value) {
+      if (nextBuilder_ == null) {
+        if (reqOneofCase_ == 3 &&
+            reqOneof_ != io.grpc.alts.internal.NextHandshakeMessageReq.getDefaultInstance()) {
+          reqOneof_ = io.grpc.alts.internal.NextHandshakeMessageReq.newBuilder((io.grpc.alts.internal.NextHandshakeMessageReq) reqOneof_)
+              .mergeFrom(value).buildPartial();
+        } else {
+          reqOneof_ = value;
+        }
+        onChanged();
+      } else {
+        if (reqOneofCase_ == 3) {
+          nextBuilder_.mergeFrom(value);
+        }
+        nextBuilder_.setMessage(value);
+      }
+      reqOneofCase_ = 3;
+      return this;
+    }
+    /**
+     * <pre>
+     * The next handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
+     */
+    public Builder clearNext() {
+      if (nextBuilder_ == null) {
+        if (reqOneofCase_ == 3) {
+          reqOneofCase_ = 0;
+          reqOneof_ = null;
+          onChanged();
+        }
+      } else {
+        if (reqOneofCase_ == 3) {
+          reqOneofCase_ = 0;
+          reqOneof_ = null;
+        }
+        nextBuilder_.clear();
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * The next handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
+     */
+    public io.grpc.alts.internal.NextHandshakeMessageReq.Builder getNextBuilder() {
+      return getNextFieldBuilder().getBuilder();
+    }
+    /**
+     * <pre>
+     * The next handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
+     */
+    public io.grpc.alts.internal.NextHandshakeMessageReqOrBuilder getNextOrBuilder() {
+      if ((reqOneofCase_ == 3) && (nextBuilder_ != null)) {
+        return nextBuilder_.getMessageOrBuilder();
+      } else {
+        if (reqOneofCase_ == 3) {
+          return (io.grpc.alts.internal.NextHandshakeMessageReq) reqOneof_;
+        }
+        return io.grpc.alts.internal.NextHandshakeMessageReq.getDefaultInstance();
+      }
+    }
+    /**
+     * <pre>
+     * The next handshake request message.
+     * </pre>
+     *
+     * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
+     */
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.NextHandshakeMessageReq, io.grpc.alts.internal.NextHandshakeMessageReq.Builder, io.grpc.alts.internal.NextHandshakeMessageReqOrBuilder> 
+        getNextFieldBuilder() {
+      if (nextBuilder_ == null) {
+        if (!(reqOneofCase_ == 3)) {
+          reqOneof_ = io.grpc.alts.internal.NextHandshakeMessageReq.getDefaultInstance();
+        }
+        nextBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
+            io.grpc.alts.internal.NextHandshakeMessageReq, io.grpc.alts.internal.NextHandshakeMessageReq.Builder, io.grpc.alts.internal.NextHandshakeMessageReqOrBuilder>(
+                (io.grpc.alts.internal.NextHandshakeMessageReq) reqOneof_,
+                getParentForChildren(),
+                isClean());
+        reqOneof_ = null;
+      }
+      reqOneofCase_ = 3;
+      onChanged();;
+      return nextBuilder_;
+    }
+    public final Builder setUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.setUnknownFieldsProto3(unknownFields);
+    }
+
+    public final Builder mergeUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.mergeUnknownFields(unknownFields);
+    }
+
+
+    // @@protoc_insertion_point(builder_scope:grpc.gcp.HandshakerReq)
+  }
+
+  // @@protoc_insertion_point(class_scope:grpc.gcp.HandshakerReq)
+  private static final io.grpc.alts.internal.HandshakerReq DEFAULT_INSTANCE;
+  static {
+    DEFAULT_INSTANCE = new io.grpc.alts.internal.HandshakerReq();
+  }
+
+  public static io.grpc.alts.internal.HandshakerReq getDefaultInstance() {
+    return DEFAULT_INSTANCE;
+  }
+
+  private static final com.google.protobuf.Parser<HandshakerReq>
+      PARSER = new com.google.protobuf.AbstractParser<HandshakerReq>() {
+    public HandshakerReq parsePartialFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return new HandshakerReq(input, extensionRegistry);
+    }
+  };
+
+  public static com.google.protobuf.Parser<HandshakerReq> parser() {
+    return PARSER;
+  }
+
+  @java.lang.Override
+  public com.google.protobuf.Parser<HandshakerReq> getParserForType() {
+    return PARSER;
+  }
+
+  public io.grpc.alts.internal.HandshakerReq getDefaultInstanceForType() {
+    return DEFAULT_INSTANCE;
+  }
+
+}
+
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerReqOrBuilder.java b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerReqOrBuilder.java
new file mode 100644
index 0000000000..5dedca8a73
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerReqOrBuilder.java
@@ -0,0 +1,86 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+public interface HandshakerReqOrBuilder extends
+    // @@protoc_insertion_point(interface_extends:grpc.gcp.HandshakerReq)
+    com.google.protobuf.MessageOrBuilder {
+
+  /**
+   * <pre>
+   * The start client handshake request message.
+   * </pre>
+   *
+   * <code>.grpc.gcp.StartClientHandshakeReq client_start = 1;</code>
+   */
+  boolean hasClientStart();
+  /**
+   * <pre>
+   * The start client handshake request message.
+   * </pre>
+   *
+   * <code>.grpc.gcp.StartClientHandshakeReq client_start = 1;</code>
+   */
+  io.grpc.alts.internal.StartClientHandshakeReq getClientStart();
+  /**
+   * <pre>
+   * The start client handshake request message.
+   * </pre>
+   *
+   * <code>.grpc.gcp.StartClientHandshakeReq client_start = 1;</code>
+   */
+  io.grpc.alts.internal.StartClientHandshakeReqOrBuilder getClientStartOrBuilder();
+
+  /**
+   * <pre>
+   * The start server handshake request message.
+   * </pre>
+   *
+   * <code>.grpc.gcp.StartServerHandshakeReq server_start = 2;</code>
+   */
+  boolean hasServerStart();
+  /**
+   * <pre>
+   * The start server handshake request message.
+   * </pre>
+   *
+   * <code>.grpc.gcp.StartServerHandshakeReq server_start = 2;</code>
+   */
+  io.grpc.alts.internal.StartServerHandshakeReq getServerStart();
+  /**
+   * <pre>
+   * The start server handshake request message.
+   * </pre>
+   *
+   * <code>.grpc.gcp.StartServerHandshakeReq server_start = 2;</code>
+   */
+  io.grpc.alts.internal.StartServerHandshakeReqOrBuilder getServerStartOrBuilder();
+
+  /**
+   * <pre>
+   * The next handshake request message.
+   * </pre>
+   *
+   * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
+   */
+  boolean hasNext();
+  /**
+   * <pre>
+   * The next handshake request message.
+   * </pre>
+   *
+   * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
+   */
+  io.grpc.alts.internal.NextHandshakeMessageReq getNext();
+  /**
+   * <pre>
+   * The next handshake request message.
+   * </pre>
+   *
+   * <code>.grpc.gcp.NextHandshakeMessageReq next = 3;</code>
+   */
+  io.grpc.alts.internal.NextHandshakeMessageReqOrBuilder getNextOrBuilder();
+
+  public io.grpc.alts.internal.HandshakerReq.ReqOneofCase getReqOneofCase();
+}
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerResp.java b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerResp.java
new file mode 100644
index 0000000000..483e5da688
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerResp.java
@@ -0,0 +1,1034 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+/**
+ * Protobuf type {@code grpc.gcp.HandshakerResp}
+ */
+public  final class HandshakerResp extends
+    com.google.protobuf.GeneratedMessageV3 implements
+    // @@protoc_insertion_point(message_implements:grpc.gcp.HandshakerResp)
+    HandshakerRespOrBuilder {
+private static final long serialVersionUID = 0L;
+  // Use HandshakerResp.newBuilder() to construct.
+  private HandshakerResp(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
+    super(builder);
+  }
+  private HandshakerResp() {
+    outFrames_ = com.google.protobuf.ByteString.EMPTY;
+    bytesConsumed_ = 0;
+  }
+
+  @java.lang.Override
+  public final com.google.protobuf.UnknownFieldSet
+  getUnknownFields() {
+    return this.unknownFields;
+  }
+  private HandshakerResp(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    this();
+    if (extensionRegistry == null) {
+      throw new java.lang.NullPointerException();
+    }
+    int mutable_bitField0_ = 0;
+    com.google.protobuf.UnknownFieldSet.Builder unknownFields =
+        com.google.protobuf.UnknownFieldSet.newBuilder();
+    try {
+      boolean done = false;
+      while (!done) {
+        int tag = input.readTag();
+        switch (tag) {
+          case 0:
+            done = true;
+            break;
+          default: {
+            if (!parseUnknownFieldProto3(
+                input, unknownFields, extensionRegistry, tag)) {
+              done = true;
+            }
+            break;
+          }
+          case 10: {
+
+            outFrames_ = input.readBytes();
+            break;
+          }
+          case 16: {
+
+            bytesConsumed_ = input.readUInt32();
+            break;
+          }
+          case 26: {
+            io.grpc.alts.internal.HandshakerResult.Builder subBuilder = null;
+            if (result_ != null) {
+              subBuilder = result_.toBuilder();
+            }
+            result_ = input.readMessage(io.grpc.alts.internal.HandshakerResult.parser(), extensionRegistry);
+            if (subBuilder != null) {
+              subBuilder.mergeFrom(result_);
+              result_ = subBuilder.buildPartial();
+            }
+
+            break;
+          }
+          case 34: {
+            io.grpc.alts.internal.HandshakerStatus.Builder subBuilder = null;
+            if (status_ != null) {
+              subBuilder = status_.toBuilder();
+            }
+            status_ = input.readMessage(io.grpc.alts.internal.HandshakerStatus.parser(), extensionRegistry);
+            if (subBuilder != null) {
+              subBuilder.mergeFrom(status_);
+              status_ = subBuilder.buildPartial();
+            }
+
+            break;
+          }
+        }
+      }
+    } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+      throw e.setUnfinishedMessage(this);
+    } catch (java.io.IOException e) {
+      throw new com.google.protobuf.InvalidProtocolBufferException(
+          e).setUnfinishedMessage(this);
+    } finally {
+      this.unknownFields = unknownFields.build();
+      makeExtensionsImmutable();
+    }
+  }
+  public static final com.google.protobuf.Descriptors.Descriptor
+      getDescriptor() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerResp_descriptor;
+  }
+
+  protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internalGetFieldAccessorTable() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerResp_fieldAccessorTable
+        .ensureFieldAccessorsInitialized(
+            io.grpc.alts.internal.HandshakerResp.class, io.grpc.alts.internal.HandshakerResp.Builder.class);
+  }
+
+  public static final int OUT_FRAMES_FIELD_NUMBER = 1;
+  private com.google.protobuf.ByteString outFrames_;
+  /**
+   * <pre>
+   * Frames to be given to the peer for the NextHandshakeMessageReq. May be
+   * empty if no out_frames have to be sent to the peer or if in_bytes in the
+   * HandshakerReq are incomplete. All the non-empty out frames must be sent to
+   * the peer even if the handshaker status is not OK as these frames may
+   * contain the alert frames.
+   * </pre>
+   *
+   * <code>bytes out_frames = 1;</code>
+   */
+  public com.google.protobuf.ByteString getOutFrames() {
+    return outFrames_;
+  }
+
+  public static final int BYTES_CONSUMED_FIELD_NUMBER = 2;
+  private int bytesConsumed_;
+  /**
+   * <pre>
+   * Number of bytes in the in_bytes consumed by the handshaker. It is possible
+   * that part of in_bytes in HandshakerReq was unrelated to the handshake
+   * process.
+   * </pre>
+   *
+   * <code>uint32 bytes_consumed = 2;</code>
+   */
+  public int getBytesConsumed() {
+    return bytesConsumed_;
+  }
+
+  public static final int RESULT_FIELD_NUMBER = 3;
+  private io.grpc.alts.internal.HandshakerResult result_;
+  /**
+   * <pre>
+   * This is set iff the handshake was successful. out_frames may still be set
+   * to frames that needs to be forwarded to the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.HandshakerResult result = 3;</code>
+   */
+  public boolean hasResult() {
+    return result_ != null;
+  }
+  /**
+   * <pre>
+   * This is set iff the handshake was successful. out_frames may still be set
+   * to frames that needs to be forwarded to the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.HandshakerResult result = 3;</code>
+   */
+  public io.grpc.alts.internal.HandshakerResult getResult() {
+    return result_ == null ? io.grpc.alts.internal.HandshakerResult.getDefaultInstance() : result_;
+  }
+  /**
+   * <pre>
+   * This is set iff the handshake was successful. out_frames may still be set
+   * to frames that needs to be forwarded to the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.HandshakerResult result = 3;</code>
+   */
+  public io.grpc.alts.internal.HandshakerResultOrBuilder getResultOrBuilder() {
+    return getResult();
+  }
+
+  public static final int STATUS_FIELD_NUMBER = 4;
+  private io.grpc.alts.internal.HandshakerStatus status_;
+  /**
+   * <pre>
+   * Status of the handshaker.
+   * </pre>
+   *
+   * <code>.grpc.gcp.HandshakerStatus status = 4;</code>
+   */
+  public boolean hasStatus() {
+    return status_ != null;
+  }
+  /**
+   * <pre>
+   * Status of the handshaker.
+   * </pre>
+   *
+   * <code>.grpc.gcp.HandshakerStatus status = 4;</code>
+   */
+  public io.grpc.alts.internal.HandshakerStatus getStatus() {
+    return status_ == null ? io.grpc.alts.internal.HandshakerStatus.getDefaultInstance() : status_;
+  }
+  /**
+   * <pre>
+   * Status of the handshaker.
+   * </pre>
+   *
+   * <code>.grpc.gcp.HandshakerStatus status = 4;</code>
+   */
+  public io.grpc.alts.internal.HandshakerStatusOrBuilder getStatusOrBuilder() {
+    return getStatus();
+  }
+
+  private byte memoizedIsInitialized = -1;
+  public final boolean isInitialized() {
+    byte isInitialized = memoizedIsInitialized;
+    if (isInitialized == 1) return true;
+    if (isInitialized == 0) return false;
+
+    memoizedIsInitialized = 1;
+    return true;
+  }
+
+  public void writeTo(com.google.protobuf.CodedOutputStream output)
+                      throws java.io.IOException {
+    if (!outFrames_.isEmpty()) {
+      output.writeBytes(1, outFrames_);
+    }
+    if (bytesConsumed_ != 0) {
+      output.writeUInt32(2, bytesConsumed_);
+    }
+    if (result_ != null) {
+      output.writeMessage(3, getResult());
+    }
+    if (status_ != null) {
+      output.writeMessage(4, getStatus());
+    }
+    unknownFields.writeTo(output);
+  }
+
+  public int getSerializedSize() {
+    int size = memoizedSize;
+    if (size != -1) return size;
+
+    size = 0;
+    if (!outFrames_.isEmpty()) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeBytesSize(1, outFrames_);
+    }
+    if (bytesConsumed_ != 0) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeUInt32Size(2, bytesConsumed_);
+    }
+    if (result_ != null) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeMessageSize(3, getResult());
+    }
+    if (status_ != null) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeMessageSize(4, getStatus());
+    }
+    size += unknownFields.getSerializedSize();
+    memoizedSize = size;
+    return size;
+  }
+
+  @java.lang.Override
+  public boolean equals(final java.lang.Object obj) {
+    if (obj == this) {
+     return true;
+    }
+    if (!(obj instanceof io.grpc.alts.internal.HandshakerResp)) {
+      return super.equals(obj);
+    }
+    io.grpc.alts.internal.HandshakerResp other = (io.grpc.alts.internal.HandshakerResp) obj;
+
+    boolean result = true;
+    result = result && getOutFrames()
+        .equals(other.getOutFrames());
+    result = result && (getBytesConsumed()
+        == other.getBytesConsumed());
+    result = result && (hasResult() == other.hasResult());
+    if (hasResult()) {
+      result = result && getResult()
+          .equals(other.getResult());
+    }
+    result = result && (hasStatus() == other.hasStatus());
+    if (hasStatus()) {
+      result = result && getStatus()
+          .equals(other.getStatus());
+    }
+    result = result && unknownFields.equals(other.unknownFields);
+    return result;
+  }
+
+  @java.lang.Override
+  public int hashCode() {
+    if (memoizedHashCode != 0) {
+      return memoizedHashCode;
+    }
+    int hash = 41;
+    hash = (19 * hash) + getDescriptor().hashCode();
+    hash = (37 * hash) + OUT_FRAMES_FIELD_NUMBER;
+    hash = (53 * hash) + getOutFrames().hashCode();
+    hash = (37 * hash) + BYTES_CONSUMED_FIELD_NUMBER;
+    hash = (53 * hash) + getBytesConsumed();
+    if (hasResult()) {
+      hash = (37 * hash) + RESULT_FIELD_NUMBER;
+      hash = (53 * hash) + getResult().hashCode();
+    }
+    if (hasStatus()) {
+      hash = (37 * hash) + STATUS_FIELD_NUMBER;
+      hash = (53 * hash) + getStatus().hashCode();
+    }
+    hash = (29 * hash) + unknownFields.hashCode();
+    memoizedHashCode = hash;
+    return hash;
+  }
+
+  public static io.grpc.alts.internal.HandshakerResp parseFrom(
+      java.nio.ByteBuffer data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.HandshakerResp parseFrom(
+      java.nio.ByteBuffer data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerResp parseFrom(
+      com.google.protobuf.ByteString data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.HandshakerResp parseFrom(
+      com.google.protobuf.ByteString data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerResp parseFrom(byte[] data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.HandshakerResp parseFrom(
+      byte[] data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerResp parseFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.HandshakerResp parseFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerResp parseDelimitedFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.HandshakerResp parseDelimitedFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerResp parseFrom(
+      com.google.protobuf.CodedInputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.HandshakerResp parseFrom(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+
+  public Builder newBuilderForType() { return newBuilder(); }
+  public static Builder newBuilder() {
+    return DEFAULT_INSTANCE.toBuilder();
+  }
+  public static Builder newBuilder(io.grpc.alts.internal.HandshakerResp prototype) {
+    return DEFAULT_INSTANCE.toBuilder().mergeFrom(prototype);
+  }
+  public Builder toBuilder() {
+    return this == DEFAULT_INSTANCE
+        ? new Builder() : new Builder().mergeFrom(this);
+  }
+
+  @java.lang.Override
+  protected Builder newBuilderForType(
+      com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+    Builder builder = new Builder(parent);
+    return builder;
+  }
+  /**
+   * Protobuf type {@code grpc.gcp.HandshakerResp}
+   */
+  public static final class Builder extends
+      com.google.protobuf.GeneratedMessageV3.Builder<Builder> implements
+      // @@protoc_insertion_point(builder_implements:grpc.gcp.HandshakerResp)
+      io.grpc.alts.internal.HandshakerRespOrBuilder {
+    public static final com.google.protobuf.Descriptors.Descriptor
+        getDescriptor() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerResp_descriptor;
+    }
+
+    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+        internalGetFieldAccessorTable() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerResp_fieldAccessorTable
+          .ensureFieldAccessorsInitialized(
+              io.grpc.alts.internal.HandshakerResp.class, io.grpc.alts.internal.HandshakerResp.Builder.class);
+    }
+
+    // Construct using io.grpc.alts.internal.HandshakerResp.newBuilder()
+    private Builder() {
+      maybeForceBuilderInitialization();
+    }
+
+    private Builder(
+        com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+      super(parent);
+      maybeForceBuilderInitialization();
+    }
+    private void maybeForceBuilderInitialization() {
+      if (com.google.protobuf.GeneratedMessageV3
+              .alwaysUseFieldBuilders) {
+      }
+    }
+    public Builder clear() {
+      super.clear();
+      outFrames_ = com.google.protobuf.ByteString.EMPTY;
+
+      bytesConsumed_ = 0;
+
+      if (resultBuilder_ == null) {
+        result_ = null;
+      } else {
+        result_ = null;
+        resultBuilder_ = null;
+      }
+      if (statusBuilder_ == null) {
+        status_ = null;
+      } else {
+        status_ = null;
+        statusBuilder_ = null;
+      }
+      return this;
+    }
+
+    public com.google.protobuf.Descriptors.Descriptor
+        getDescriptorForType() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerResp_descriptor;
+    }
+
+    public io.grpc.alts.internal.HandshakerResp getDefaultInstanceForType() {
+      return io.grpc.alts.internal.HandshakerResp.getDefaultInstance();
+    }
+
+    public io.grpc.alts.internal.HandshakerResp build() {
+      io.grpc.alts.internal.HandshakerResp result = buildPartial();
+      if (!result.isInitialized()) {
+        throw newUninitializedMessageException(result);
+      }
+      return result;
+    }
+
+    public io.grpc.alts.internal.HandshakerResp buildPartial() {
+      io.grpc.alts.internal.HandshakerResp result = new io.grpc.alts.internal.HandshakerResp(this);
+      result.outFrames_ = outFrames_;
+      result.bytesConsumed_ = bytesConsumed_;
+      if (resultBuilder_ == null) {
+        result.result_ = result_;
+      } else {
+        result.result_ = resultBuilder_.build();
+      }
+      if (statusBuilder_ == null) {
+        result.status_ = status_;
+      } else {
+        result.status_ = statusBuilder_.build();
+      }
+      onBuilt();
+      return result;
+    }
+
+    public Builder clone() {
+      return (Builder) super.clone();
+    }
+    public Builder setField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.setField(field, value);
+    }
+    public Builder clearField(
+        com.google.protobuf.Descriptors.FieldDescriptor field) {
+      return (Builder) super.clearField(field);
+    }
+    public Builder clearOneof(
+        com.google.protobuf.Descriptors.OneofDescriptor oneof) {
+      return (Builder) super.clearOneof(oneof);
+    }
+    public Builder setRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        int index, java.lang.Object value) {
+      return (Builder) super.setRepeatedField(field, index, value);
+    }
+    public Builder addRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.addRepeatedField(field, value);
+    }
+    public Builder mergeFrom(com.google.protobuf.Message other) {
+      if (other instanceof io.grpc.alts.internal.HandshakerResp) {
+        return mergeFrom((io.grpc.alts.internal.HandshakerResp)other);
+      } else {
+        super.mergeFrom(other);
+        return this;
+      }
+    }
+
+    public Builder mergeFrom(io.grpc.alts.internal.HandshakerResp other) {
+      if (other == io.grpc.alts.internal.HandshakerResp.getDefaultInstance()) return this;
+      if (other.getOutFrames() != com.google.protobuf.ByteString.EMPTY) {
+        setOutFrames(other.getOutFrames());
+      }
+      if (other.getBytesConsumed() != 0) {
+        setBytesConsumed(other.getBytesConsumed());
+      }
+      if (other.hasResult()) {
+        mergeResult(other.getResult());
+      }
+      if (other.hasStatus()) {
+        mergeStatus(other.getStatus());
+      }
+      this.mergeUnknownFields(other.unknownFields);
+      onChanged();
+      return this;
+    }
+
+    public final boolean isInitialized() {
+      return true;
+    }
+
+    public Builder mergeFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      io.grpc.alts.internal.HandshakerResp parsedMessage = null;
+      try {
+        parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);
+      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+        parsedMessage = (io.grpc.alts.internal.HandshakerResp) e.getUnfinishedMessage();
+        throw e.unwrapIOException();
+      } finally {
+        if (parsedMessage != null) {
+          mergeFrom(parsedMessage);
+        }
+      }
+      return this;
+    }
+
+    private com.google.protobuf.ByteString outFrames_ = com.google.protobuf.ByteString.EMPTY;
+    /**
+     * <pre>
+     * Frames to be given to the peer for the NextHandshakeMessageReq. May be
+     * empty if no out_frames have to be sent to the peer or if in_bytes in the
+     * HandshakerReq are incomplete. All the non-empty out frames must be sent to
+     * the peer even if the handshaker status is not OK as these frames may
+     * contain the alert frames.
+     * </pre>
+     *
+     * <code>bytes out_frames = 1;</code>
+     */
+    public com.google.protobuf.ByteString getOutFrames() {
+      return outFrames_;
+    }
+    /**
+     * <pre>
+     * Frames to be given to the peer for the NextHandshakeMessageReq. May be
+     * empty if no out_frames have to be sent to the peer or if in_bytes in the
+     * HandshakerReq are incomplete. All the non-empty out frames must be sent to
+     * the peer even if the handshaker status is not OK as these frames may
+     * contain the alert frames.
+     * </pre>
+     *
+     * <code>bytes out_frames = 1;</code>
+     */
+    public Builder setOutFrames(com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  
+      outFrames_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * Frames to be given to the peer for the NextHandshakeMessageReq. May be
+     * empty if no out_frames have to be sent to the peer or if in_bytes in the
+     * HandshakerReq are incomplete. All the non-empty out frames must be sent to
+     * the peer even if the handshaker status is not OK as these frames may
+     * contain the alert frames.
+     * </pre>
+     *
+     * <code>bytes out_frames = 1;</code>
+     */
+    public Builder clearOutFrames() {
+      
+      outFrames_ = getDefaultInstance().getOutFrames();
+      onChanged();
+      return this;
+    }
+
+    private int bytesConsumed_ ;
+    /**
+     * <pre>
+     * Number of bytes in the in_bytes consumed by the handshaker. It is possible
+     * that part of in_bytes in HandshakerReq was unrelated to the handshake
+     * process.
+     * </pre>
+     *
+     * <code>uint32 bytes_consumed = 2;</code>
+     */
+    public int getBytesConsumed() {
+      return bytesConsumed_;
+    }
+    /**
+     * <pre>
+     * Number of bytes in the in_bytes consumed by the handshaker. It is possible
+     * that part of in_bytes in HandshakerReq was unrelated to the handshake
+     * process.
+     * </pre>
+     *
+     * <code>uint32 bytes_consumed = 2;</code>
+     */
+    public Builder setBytesConsumed(int value) {
+      
+      bytesConsumed_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * Number of bytes in the in_bytes consumed by the handshaker. It is possible
+     * that part of in_bytes in HandshakerReq was unrelated to the handshake
+     * process.
+     * </pre>
+     *
+     * <code>uint32 bytes_consumed = 2;</code>
+     */
+    public Builder clearBytesConsumed() {
+      
+      bytesConsumed_ = 0;
+      onChanged();
+      return this;
+    }
+
+    private io.grpc.alts.internal.HandshakerResult result_ = null;
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.HandshakerResult, io.grpc.alts.internal.HandshakerResult.Builder, io.grpc.alts.internal.HandshakerResultOrBuilder> resultBuilder_;
+    /**
+     * <pre>
+     * This is set iff the handshake was successful. out_frames may still be set
+     * to frames that needs to be forwarded to the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakerResult result = 3;</code>
+     */
+    public boolean hasResult() {
+      return resultBuilder_ != null || result_ != null;
+    }
+    /**
+     * <pre>
+     * This is set iff the handshake was successful. out_frames may still be set
+     * to frames that needs to be forwarded to the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakerResult result = 3;</code>
+     */
+    public io.grpc.alts.internal.HandshakerResult getResult() {
+      if (resultBuilder_ == null) {
+        return result_ == null ? io.grpc.alts.internal.HandshakerResult.getDefaultInstance() : result_;
+      } else {
+        return resultBuilder_.getMessage();
+      }
+    }
+    /**
+     * <pre>
+     * This is set iff the handshake was successful. out_frames may still be set
+     * to frames that needs to be forwarded to the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakerResult result = 3;</code>
+     */
+    public Builder setResult(io.grpc.alts.internal.HandshakerResult value) {
+      if (resultBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        result_ = value;
+        onChanged();
+      } else {
+        resultBuilder_.setMessage(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * This is set iff the handshake was successful. out_frames may still be set
+     * to frames that needs to be forwarded to the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakerResult result = 3;</code>
+     */
+    public Builder setResult(
+        io.grpc.alts.internal.HandshakerResult.Builder builderForValue) {
+      if (resultBuilder_ == null) {
+        result_ = builderForValue.build();
+        onChanged();
+      } else {
+        resultBuilder_.setMessage(builderForValue.build());
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * This is set iff the handshake was successful. out_frames may still be set
+     * to frames that needs to be forwarded to the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakerResult result = 3;</code>
+     */
+    public Builder mergeResult(io.grpc.alts.internal.HandshakerResult value) {
+      if (resultBuilder_ == null) {
+        if (result_ != null) {
+          result_ =
+            io.grpc.alts.internal.HandshakerResult.newBuilder(result_).mergeFrom(value).buildPartial();
+        } else {
+          result_ = value;
+        }
+        onChanged();
+      } else {
+        resultBuilder_.mergeFrom(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * This is set iff the handshake was successful. out_frames may still be set
+     * to frames that needs to be forwarded to the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakerResult result = 3;</code>
+     */
+    public Builder clearResult() {
+      if (resultBuilder_ == null) {
+        result_ = null;
+        onChanged();
+      } else {
+        result_ = null;
+        resultBuilder_ = null;
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * This is set iff the handshake was successful. out_frames may still be set
+     * to frames that needs to be forwarded to the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakerResult result = 3;</code>
+     */
+    public io.grpc.alts.internal.HandshakerResult.Builder getResultBuilder() {
+      
+      onChanged();
+      return getResultFieldBuilder().getBuilder();
+    }
+    /**
+     * <pre>
+     * This is set iff the handshake was successful. out_frames may still be set
+     * to frames that needs to be forwarded to the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakerResult result = 3;</code>
+     */
+    public io.grpc.alts.internal.HandshakerResultOrBuilder getResultOrBuilder() {
+      if (resultBuilder_ != null) {
+        return resultBuilder_.getMessageOrBuilder();
+      } else {
+        return result_ == null ?
+            io.grpc.alts.internal.HandshakerResult.getDefaultInstance() : result_;
+      }
+    }
+    /**
+     * <pre>
+     * This is set iff the handshake was successful. out_frames may still be set
+     * to frames that needs to be forwarded to the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakerResult result = 3;</code>
+     */
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.HandshakerResult, io.grpc.alts.internal.HandshakerResult.Builder, io.grpc.alts.internal.HandshakerResultOrBuilder> 
+        getResultFieldBuilder() {
+      if (resultBuilder_ == null) {
+        resultBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
+            io.grpc.alts.internal.HandshakerResult, io.grpc.alts.internal.HandshakerResult.Builder, io.grpc.alts.internal.HandshakerResultOrBuilder>(
+                getResult(),
+                getParentForChildren(),
+                isClean());
+        result_ = null;
+      }
+      return resultBuilder_;
+    }
+
+    private io.grpc.alts.internal.HandshakerStatus status_ = null;
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.HandshakerStatus, io.grpc.alts.internal.HandshakerStatus.Builder, io.grpc.alts.internal.HandshakerStatusOrBuilder> statusBuilder_;
+    /**
+     * <pre>
+     * Status of the handshaker.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakerStatus status = 4;</code>
+     */
+    public boolean hasStatus() {
+      return statusBuilder_ != null || status_ != null;
+    }
+    /**
+     * <pre>
+     * Status of the handshaker.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakerStatus status = 4;</code>
+     */
+    public io.grpc.alts.internal.HandshakerStatus getStatus() {
+      if (statusBuilder_ == null) {
+        return status_ == null ? io.grpc.alts.internal.HandshakerStatus.getDefaultInstance() : status_;
+      } else {
+        return statusBuilder_.getMessage();
+      }
+    }
+    /**
+     * <pre>
+     * Status of the handshaker.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakerStatus status = 4;</code>
+     */
+    public Builder setStatus(io.grpc.alts.internal.HandshakerStatus value) {
+      if (statusBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        status_ = value;
+        onChanged();
+      } else {
+        statusBuilder_.setMessage(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * Status of the handshaker.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakerStatus status = 4;</code>
+     */
+    public Builder setStatus(
+        io.grpc.alts.internal.HandshakerStatus.Builder builderForValue) {
+      if (statusBuilder_ == null) {
+        status_ = builderForValue.build();
+        onChanged();
+      } else {
+        statusBuilder_.setMessage(builderForValue.build());
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * Status of the handshaker.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakerStatus status = 4;</code>
+     */
+    public Builder mergeStatus(io.grpc.alts.internal.HandshakerStatus value) {
+      if (statusBuilder_ == null) {
+        if (status_ != null) {
+          status_ =
+            io.grpc.alts.internal.HandshakerStatus.newBuilder(status_).mergeFrom(value).buildPartial();
+        } else {
+          status_ = value;
+        }
+        onChanged();
+      } else {
+        statusBuilder_.mergeFrom(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * Status of the handshaker.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakerStatus status = 4;</code>
+     */
+    public Builder clearStatus() {
+      if (statusBuilder_ == null) {
+        status_ = null;
+        onChanged();
+      } else {
+        status_ = null;
+        statusBuilder_ = null;
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * Status of the handshaker.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakerStatus status = 4;</code>
+     */
+    public io.grpc.alts.internal.HandshakerStatus.Builder getStatusBuilder() {
+      
+      onChanged();
+      return getStatusFieldBuilder().getBuilder();
+    }
+    /**
+     * <pre>
+     * Status of the handshaker.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakerStatus status = 4;</code>
+     */
+    public io.grpc.alts.internal.HandshakerStatusOrBuilder getStatusOrBuilder() {
+      if (statusBuilder_ != null) {
+        return statusBuilder_.getMessageOrBuilder();
+      } else {
+        return status_ == null ?
+            io.grpc.alts.internal.HandshakerStatus.getDefaultInstance() : status_;
+      }
+    }
+    /**
+     * <pre>
+     * Status of the handshaker.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakerStatus status = 4;</code>
+     */
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.HandshakerStatus, io.grpc.alts.internal.HandshakerStatus.Builder, io.grpc.alts.internal.HandshakerStatusOrBuilder> 
+        getStatusFieldBuilder() {
+      if (statusBuilder_ == null) {
+        statusBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
+            io.grpc.alts.internal.HandshakerStatus, io.grpc.alts.internal.HandshakerStatus.Builder, io.grpc.alts.internal.HandshakerStatusOrBuilder>(
+                getStatus(),
+                getParentForChildren(),
+                isClean());
+        status_ = null;
+      }
+      return statusBuilder_;
+    }
+    public final Builder setUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.setUnknownFieldsProto3(unknownFields);
+    }
+
+    public final Builder mergeUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.mergeUnknownFields(unknownFields);
+    }
+
+
+    // @@protoc_insertion_point(builder_scope:grpc.gcp.HandshakerResp)
+  }
+
+  // @@protoc_insertion_point(class_scope:grpc.gcp.HandshakerResp)
+  private static final io.grpc.alts.internal.HandshakerResp DEFAULT_INSTANCE;
+  static {
+    DEFAULT_INSTANCE = new io.grpc.alts.internal.HandshakerResp();
+  }
+
+  public static io.grpc.alts.internal.HandshakerResp getDefaultInstance() {
+    return DEFAULT_INSTANCE;
+  }
+
+  private static final com.google.protobuf.Parser<HandshakerResp>
+      PARSER = new com.google.protobuf.AbstractParser<HandshakerResp>() {
+    public HandshakerResp parsePartialFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return new HandshakerResp(input, extensionRegistry);
+    }
+  };
+
+  public static com.google.protobuf.Parser<HandshakerResp> parser() {
+    return PARSER;
+  }
+
+  @java.lang.Override
+  public com.google.protobuf.Parser<HandshakerResp> getParserForType() {
+    return PARSER;
+  }
+
+  public io.grpc.alts.internal.HandshakerResp getDefaultInstanceForType() {
+    return DEFAULT_INSTANCE;
+  }
+
+}
+
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerRespOrBuilder.java b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerRespOrBuilder.java
new file mode 100644
index 0000000000..e75909bf17
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerRespOrBuilder.java
@@ -0,0 +1,86 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+public interface HandshakerRespOrBuilder extends
+    // @@protoc_insertion_point(interface_extends:grpc.gcp.HandshakerResp)
+    com.google.protobuf.MessageOrBuilder {
+
+  /**
+   * <pre>
+   * Frames to be given to the peer for the NextHandshakeMessageReq. May be
+   * empty if no out_frames have to be sent to the peer or if in_bytes in the
+   * HandshakerReq are incomplete. All the non-empty out frames must be sent to
+   * the peer even if the handshaker status is not OK as these frames may
+   * contain the alert frames.
+   * </pre>
+   *
+   * <code>bytes out_frames = 1;</code>
+   */
+  com.google.protobuf.ByteString getOutFrames();
+
+  /**
+   * <pre>
+   * Number of bytes in the in_bytes consumed by the handshaker. It is possible
+   * that part of in_bytes in HandshakerReq was unrelated to the handshake
+   * process.
+   * </pre>
+   *
+   * <code>uint32 bytes_consumed = 2;</code>
+   */
+  int getBytesConsumed();
+
+  /**
+   * <pre>
+   * This is set iff the handshake was successful. out_frames may still be set
+   * to frames that needs to be forwarded to the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.HandshakerResult result = 3;</code>
+   */
+  boolean hasResult();
+  /**
+   * <pre>
+   * This is set iff the handshake was successful. out_frames may still be set
+   * to frames that needs to be forwarded to the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.HandshakerResult result = 3;</code>
+   */
+  io.grpc.alts.internal.HandshakerResult getResult();
+  /**
+   * <pre>
+   * This is set iff the handshake was successful. out_frames may still be set
+   * to frames that needs to be forwarded to the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.HandshakerResult result = 3;</code>
+   */
+  io.grpc.alts.internal.HandshakerResultOrBuilder getResultOrBuilder();
+
+  /**
+   * <pre>
+   * Status of the handshaker.
+   * </pre>
+   *
+   * <code>.grpc.gcp.HandshakerStatus status = 4;</code>
+   */
+  boolean hasStatus();
+  /**
+   * <pre>
+   * Status of the handshaker.
+   * </pre>
+   *
+   * <code>.grpc.gcp.HandshakerStatus status = 4;</code>
+   */
+  io.grpc.alts.internal.HandshakerStatus getStatus();
+  /**
+   * <pre>
+   * Status of the handshaker.
+   * </pre>
+   *
+   * <code>.grpc.gcp.HandshakerStatus status = 4;</code>
+   */
+  io.grpc.alts.internal.HandshakerStatusOrBuilder getStatusOrBuilder();
+}
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerResult.java b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerResult.java
new file mode 100644
index 0000000000..16680c73a3
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerResult.java
@@ -0,0 +1,1554 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+/**
+ * Protobuf type {@code grpc.gcp.HandshakerResult}
+ */
+public  final class HandshakerResult extends
+    com.google.protobuf.GeneratedMessageV3 implements
+    // @@protoc_insertion_point(message_implements:grpc.gcp.HandshakerResult)
+    HandshakerResultOrBuilder {
+private static final long serialVersionUID = 0L;
+  // Use HandshakerResult.newBuilder() to construct.
+  private HandshakerResult(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
+    super(builder);
+  }
+  private HandshakerResult() {
+    applicationProtocol_ = "";
+    recordProtocol_ = "";
+    keyData_ = com.google.protobuf.ByteString.EMPTY;
+    keepChannelOpen_ = false;
+  }
+
+  @java.lang.Override
+  public final com.google.protobuf.UnknownFieldSet
+  getUnknownFields() {
+    return this.unknownFields;
+  }
+  private HandshakerResult(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    this();
+    if (extensionRegistry == null) {
+      throw new java.lang.NullPointerException();
+    }
+    int mutable_bitField0_ = 0;
+    com.google.protobuf.UnknownFieldSet.Builder unknownFields =
+        com.google.protobuf.UnknownFieldSet.newBuilder();
+    try {
+      boolean done = false;
+      while (!done) {
+        int tag = input.readTag();
+        switch (tag) {
+          case 0:
+            done = true;
+            break;
+          default: {
+            if (!parseUnknownFieldProto3(
+                input, unknownFields, extensionRegistry, tag)) {
+              done = true;
+            }
+            break;
+          }
+          case 10: {
+            java.lang.String s = input.readStringRequireUtf8();
+
+            applicationProtocol_ = s;
+            break;
+          }
+          case 18: {
+            java.lang.String s = input.readStringRequireUtf8();
+
+            recordProtocol_ = s;
+            break;
+          }
+          case 26: {
+
+            keyData_ = input.readBytes();
+            break;
+          }
+          case 34: {
+            io.grpc.alts.internal.Identity.Builder subBuilder = null;
+            if (peerIdentity_ != null) {
+              subBuilder = peerIdentity_.toBuilder();
+            }
+            peerIdentity_ = input.readMessage(io.grpc.alts.internal.Identity.parser(), extensionRegistry);
+            if (subBuilder != null) {
+              subBuilder.mergeFrom(peerIdentity_);
+              peerIdentity_ = subBuilder.buildPartial();
+            }
+
+            break;
+          }
+          case 42: {
+            io.grpc.alts.internal.Identity.Builder subBuilder = null;
+            if (localIdentity_ != null) {
+              subBuilder = localIdentity_.toBuilder();
+            }
+            localIdentity_ = input.readMessage(io.grpc.alts.internal.Identity.parser(), extensionRegistry);
+            if (subBuilder != null) {
+              subBuilder.mergeFrom(localIdentity_);
+              localIdentity_ = subBuilder.buildPartial();
+            }
+
+            break;
+          }
+          case 48: {
+
+            keepChannelOpen_ = input.readBool();
+            break;
+          }
+          case 58: {
+            io.grpc.alts.internal.RpcProtocolVersions.Builder subBuilder = null;
+            if (peerRpcVersions_ != null) {
+              subBuilder = peerRpcVersions_.toBuilder();
+            }
+            peerRpcVersions_ = input.readMessage(io.grpc.alts.internal.RpcProtocolVersions.parser(), extensionRegistry);
+            if (subBuilder != null) {
+              subBuilder.mergeFrom(peerRpcVersions_);
+              peerRpcVersions_ = subBuilder.buildPartial();
+            }
+
+            break;
+          }
+        }
+      }
+    } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+      throw e.setUnfinishedMessage(this);
+    } catch (java.io.IOException e) {
+      throw new com.google.protobuf.InvalidProtocolBufferException(
+          e).setUnfinishedMessage(this);
+    } finally {
+      this.unknownFields = unknownFields.build();
+      makeExtensionsImmutable();
+    }
+  }
+  public static final com.google.protobuf.Descriptors.Descriptor
+      getDescriptor() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerResult_descriptor;
+  }
+
+  protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internalGetFieldAccessorTable() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerResult_fieldAccessorTable
+        .ensureFieldAccessorsInitialized(
+            io.grpc.alts.internal.HandshakerResult.class, io.grpc.alts.internal.HandshakerResult.Builder.class);
+  }
+
+  public static final int APPLICATION_PROTOCOL_FIELD_NUMBER = 1;
+  private volatile java.lang.Object applicationProtocol_;
+  /**
+   * <pre>
+   * The application protocol negotiated for this connection.
+   * </pre>
+   *
+   * <code>string application_protocol = 1;</code>
+   */
+  public java.lang.String getApplicationProtocol() {
+    java.lang.Object ref = applicationProtocol_;
+    if (ref instanceof java.lang.String) {
+      return (java.lang.String) ref;
+    } else {
+      com.google.protobuf.ByteString bs = 
+          (com.google.protobuf.ByteString) ref;
+      java.lang.String s = bs.toStringUtf8();
+      applicationProtocol_ = s;
+      return s;
+    }
+  }
+  /**
+   * <pre>
+   * The application protocol negotiated for this connection.
+   * </pre>
+   *
+   * <code>string application_protocol = 1;</code>
+   */
+  public com.google.protobuf.ByteString
+      getApplicationProtocolBytes() {
+    java.lang.Object ref = applicationProtocol_;
+    if (ref instanceof java.lang.String) {
+      com.google.protobuf.ByteString b = 
+          com.google.protobuf.ByteString.copyFromUtf8(
+              (java.lang.String) ref);
+      applicationProtocol_ = b;
+      return b;
+    } else {
+      return (com.google.protobuf.ByteString) ref;
+    }
+  }
+
+  public static final int RECORD_PROTOCOL_FIELD_NUMBER = 2;
+  private volatile java.lang.Object recordProtocol_;
+  /**
+   * <pre>
+   * The record protocol negotiated for this connection.
+   * </pre>
+   *
+   * <code>string record_protocol = 2;</code>
+   */
+  public java.lang.String getRecordProtocol() {
+    java.lang.Object ref = recordProtocol_;
+    if (ref instanceof java.lang.String) {
+      return (java.lang.String) ref;
+    } else {
+      com.google.protobuf.ByteString bs = 
+          (com.google.protobuf.ByteString) ref;
+      java.lang.String s = bs.toStringUtf8();
+      recordProtocol_ = s;
+      return s;
+    }
+  }
+  /**
+   * <pre>
+   * The record protocol negotiated for this connection.
+   * </pre>
+   *
+   * <code>string record_protocol = 2;</code>
+   */
+  public com.google.protobuf.ByteString
+      getRecordProtocolBytes() {
+    java.lang.Object ref = recordProtocol_;
+    if (ref instanceof java.lang.String) {
+      com.google.protobuf.ByteString b = 
+          com.google.protobuf.ByteString.copyFromUtf8(
+              (java.lang.String) ref);
+      recordProtocol_ = b;
+      return b;
+    } else {
+      return (com.google.protobuf.ByteString) ref;
+    }
+  }
+
+  public static final int KEY_DATA_FIELD_NUMBER = 3;
+  private com.google.protobuf.ByteString keyData_;
+  /**
+   * <pre>
+   * Cryptographic key data. The key data may be more than the key length
+   * required for the record protocol, thus the client of the handshaker
+   * service needs to truncate the key data into the right key length.
+   * </pre>
+   *
+   * <code>bytes key_data = 3;</code>
+   */
+  public com.google.protobuf.ByteString getKeyData() {
+    return keyData_;
+  }
+
+  public static final int PEER_IDENTITY_FIELD_NUMBER = 4;
+  private io.grpc.alts.internal.Identity peerIdentity_;
+  /**
+   * <pre>
+   * The authenticated identity of the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Identity peer_identity = 4;</code>
+   */
+  public boolean hasPeerIdentity() {
+    return peerIdentity_ != null;
+  }
+  /**
+   * <pre>
+   * The authenticated identity of the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Identity peer_identity = 4;</code>
+   */
+  public io.grpc.alts.internal.Identity getPeerIdentity() {
+    return peerIdentity_ == null ? io.grpc.alts.internal.Identity.getDefaultInstance() : peerIdentity_;
+  }
+  /**
+   * <pre>
+   * The authenticated identity of the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Identity peer_identity = 4;</code>
+   */
+  public io.grpc.alts.internal.IdentityOrBuilder getPeerIdentityOrBuilder() {
+    return getPeerIdentity();
+  }
+
+  public static final int LOCAL_IDENTITY_FIELD_NUMBER = 5;
+  private io.grpc.alts.internal.Identity localIdentity_;
+  /**
+   * <pre>
+   * The local identity used in the handshake.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Identity local_identity = 5;</code>
+   */
+  public boolean hasLocalIdentity() {
+    return localIdentity_ != null;
+  }
+  /**
+   * <pre>
+   * The local identity used in the handshake.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Identity local_identity = 5;</code>
+   */
+  public io.grpc.alts.internal.Identity getLocalIdentity() {
+    return localIdentity_ == null ? io.grpc.alts.internal.Identity.getDefaultInstance() : localIdentity_;
+  }
+  /**
+   * <pre>
+   * The local identity used in the handshake.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Identity local_identity = 5;</code>
+   */
+  public io.grpc.alts.internal.IdentityOrBuilder getLocalIdentityOrBuilder() {
+    return getLocalIdentity();
+  }
+
+  public static final int KEEP_CHANNEL_OPEN_FIELD_NUMBER = 6;
+  private boolean keepChannelOpen_;
+  /**
+   * <pre>
+   * Indicate whether the handshaker service client should keep the channel
+   * between the handshaker service open, e.g., in order to handle
+   * post-handshake messages in the future.
+   * </pre>
+   *
+   * <code>bool keep_channel_open = 6;</code>
+   */
+  public boolean getKeepChannelOpen() {
+    return keepChannelOpen_;
+  }
+
+  public static final int PEER_RPC_VERSIONS_FIELD_NUMBER = 7;
+  private io.grpc.alts.internal.RpcProtocolVersions peerRpcVersions_;
+  /**
+   * <pre>
+   * The RPC protocol versions supported by the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
+   */
+  public boolean hasPeerRpcVersions() {
+    return peerRpcVersions_ != null;
+  }
+  /**
+   * <pre>
+   * The RPC protocol versions supported by the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
+   */
+  public io.grpc.alts.internal.RpcProtocolVersions getPeerRpcVersions() {
+    return peerRpcVersions_ == null ? io.grpc.alts.internal.RpcProtocolVersions.getDefaultInstance() : peerRpcVersions_;
+  }
+  /**
+   * <pre>
+   * The RPC protocol versions supported by the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
+   */
+  public io.grpc.alts.internal.RpcProtocolVersionsOrBuilder getPeerRpcVersionsOrBuilder() {
+    return getPeerRpcVersions();
+  }
+
+  private byte memoizedIsInitialized = -1;
+  public final boolean isInitialized() {
+    byte isInitialized = memoizedIsInitialized;
+    if (isInitialized == 1) return true;
+    if (isInitialized == 0) return false;
+
+    memoizedIsInitialized = 1;
+    return true;
+  }
+
+  public void writeTo(com.google.protobuf.CodedOutputStream output)
+                      throws java.io.IOException {
+    if (!getApplicationProtocolBytes().isEmpty()) {
+      com.google.protobuf.GeneratedMessageV3.writeString(output, 1, applicationProtocol_);
+    }
+    if (!getRecordProtocolBytes().isEmpty()) {
+      com.google.protobuf.GeneratedMessageV3.writeString(output, 2, recordProtocol_);
+    }
+    if (!keyData_.isEmpty()) {
+      output.writeBytes(3, keyData_);
+    }
+    if (peerIdentity_ != null) {
+      output.writeMessage(4, getPeerIdentity());
+    }
+    if (localIdentity_ != null) {
+      output.writeMessage(5, getLocalIdentity());
+    }
+    if (keepChannelOpen_ != false) {
+      output.writeBool(6, keepChannelOpen_);
+    }
+    if (peerRpcVersions_ != null) {
+      output.writeMessage(7, getPeerRpcVersions());
+    }
+    unknownFields.writeTo(output);
+  }
+
+  public int getSerializedSize() {
+    int size = memoizedSize;
+    if (size != -1) return size;
+
+    size = 0;
+    if (!getApplicationProtocolBytes().isEmpty()) {
+      size += com.google.protobuf.GeneratedMessageV3.computeStringSize(1, applicationProtocol_);
+    }
+    if (!getRecordProtocolBytes().isEmpty()) {
+      size += com.google.protobuf.GeneratedMessageV3.computeStringSize(2, recordProtocol_);
+    }
+    if (!keyData_.isEmpty()) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeBytesSize(3, keyData_);
+    }
+    if (peerIdentity_ != null) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeMessageSize(4, getPeerIdentity());
+    }
+    if (localIdentity_ != null) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeMessageSize(5, getLocalIdentity());
+    }
+    if (keepChannelOpen_ != false) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeBoolSize(6, keepChannelOpen_);
+    }
+    if (peerRpcVersions_ != null) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeMessageSize(7, getPeerRpcVersions());
+    }
+    size += unknownFields.getSerializedSize();
+    memoizedSize = size;
+    return size;
+  }
+
+  @java.lang.Override
+  public boolean equals(final java.lang.Object obj) {
+    if (obj == this) {
+     return true;
+    }
+    if (!(obj instanceof io.grpc.alts.internal.HandshakerResult)) {
+      return super.equals(obj);
+    }
+    io.grpc.alts.internal.HandshakerResult other = (io.grpc.alts.internal.HandshakerResult) obj;
+
+    boolean result = true;
+    result = result && getApplicationProtocol()
+        .equals(other.getApplicationProtocol());
+    result = result && getRecordProtocol()
+        .equals(other.getRecordProtocol());
+    result = result && getKeyData()
+        .equals(other.getKeyData());
+    result = result && (hasPeerIdentity() == other.hasPeerIdentity());
+    if (hasPeerIdentity()) {
+      result = result && getPeerIdentity()
+          .equals(other.getPeerIdentity());
+    }
+    result = result && (hasLocalIdentity() == other.hasLocalIdentity());
+    if (hasLocalIdentity()) {
+      result = result && getLocalIdentity()
+          .equals(other.getLocalIdentity());
+    }
+    result = result && (getKeepChannelOpen()
+        == other.getKeepChannelOpen());
+    result = result && (hasPeerRpcVersions() == other.hasPeerRpcVersions());
+    if (hasPeerRpcVersions()) {
+      result = result && getPeerRpcVersions()
+          .equals(other.getPeerRpcVersions());
+    }
+    result = result && unknownFields.equals(other.unknownFields);
+    return result;
+  }
+
+  @java.lang.Override
+  public int hashCode() {
+    if (memoizedHashCode != 0) {
+      return memoizedHashCode;
+    }
+    int hash = 41;
+    hash = (19 * hash) + getDescriptor().hashCode();
+    hash = (37 * hash) + APPLICATION_PROTOCOL_FIELD_NUMBER;
+    hash = (53 * hash) + getApplicationProtocol().hashCode();
+    hash = (37 * hash) + RECORD_PROTOCOL_FIELD_NUMBER;
+    hash = (53 * hash) + getRecordProtocol().hashCode();
+    hash = (37 * hash) + KEY_DATA_FIELD_NUMBER;
+    hash = (53 * hash) + getKeyData().hashCode();
+    if (hasPeerIdentity()) {
+      hash = (37 * hash) + PEER_IDENTITY_FIELD_NUMBER;
+      hash = (53 * hash) + getPeerIdentity().hashCode();
+    }
+    if (hasLocalIdentity()) {
+      hash = (37 * hash) + LOCAL_IDENTITY_FIELD_NUMBER;
+      hash = (53 * hash) + getLocalIdentity().hashCode();
+    }
+    hash = (37 * hash) + KEEP_CHANNEL_OPEN_FIELD_NUMBER;
+    hash = (53 * hash) + com.google.protobuf.Internal.hashBoolean(
+        getKeepChannelOpen());
+    if (hasPeerRpcVersions()) {
+      hash = (37 * hash) + PEER_RPC_VERSIONS_FIELD_NUMBER;
+      hash = (53 * hash) + getPeerRpcVersions().hashCode();
+    }
+    hash = (29 * hash) + unknownFields.hashCode();
+    memoizedHashCode = hash;
+    return hash;
+  }
+
+  public static io.grpc.alts.internal.HandshakerResult parseFrom(
+      java.nio.ByteBuffer data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.HandshakerResult parseFrom(
+      java.nio.ByteBuffer data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerResult parseFrom(
+      com.google.protobuf.ByteString data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.HandshakerResult parseFrom(
+      com.google.protobuf.ByteString data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerResult parseFrom(byte[] data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.HandshakerResult parseFrom(
+      byte[] data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerResult parseFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.HandshakerResult parseFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerResult parseDelimitedFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.HandshakerResult parseDelimitedFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerResult parseFrom(
+      com.google.protobuf.CodedInputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.HandshakerResult parseFrom(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+
+  public Builder newBuilderForType() { return newBuilder(); }
+  public static Builder newBuilder() {
+    return DEFAULT_INSTANCE.toBuilder();
+  }
+  public static Builder newBuilder(io.grpc.alts.internal.HandshakerResult prototype) {
+    return DEFAULT_INSTANCE.toBuilder().mergeFrom(prototype);
+  }
+  public Builder toBuilder() {
+    return this == DEFAULT_INSTANCE
+        ? new Builder() : new Builder().mergeFrom(this);
+  }
+
+  @java.lang.Override
+  protected Builder newBuilderForType(
+      com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+    Builder builder = new Builder(parent);
+    return builder;
+  }
+  /**
+   * Protobuf type {@code grpc.gcp.HandshakerResult}
+   */
+  public static final class Builder extends
+      com.google.protobuf.GeneratedMessageV3.Builder<Builder> implements
+      // @@protoc_insertion_point(builder_implements:grpc.gcp.HandshakerResult)
+      io.grpc.alts.internal.HandshakerResultOrBuilder {
+    public static final com.google.protobuf.Descriptors.Descriptor
+        getDescriptor() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerResult_descriptor;
+    }
+
+    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+        internalGetFieldAccessorTable() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerResult_fieldAccessorTable
+          .ensureFieldAccessorsInitialized(
+              io.grpc.alts.internal.HandshakerResult.class, io.grpc.alts.internal.HandshakerResult.Builder.class);
+    }
+
+    // Construct using io.grpc.alts.internal.HandshakerResult.newBuilder()
+    private Builder() {
+      maybeForceBuilderInitialization();
+    }
+
+    private Builder(
+        com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+      super(parent);
+      maybeForceBuilderInitialization();
+    }
+    private void maybeForceBuilderInitialization() {
+      if (com.google.protobuf.GeneratedMessageV3
+              .alwaysUseFieldBuilders) {
+      }
+    }
+    public Builder clear() {
+      super.clear();
+      applicationProtocol_ = "";
+
+      recordProtocol_ = "";
+
+      keyData_ = com.google.protobuf.ByteString.EMPTY;
+
+      if (peerIdentityBuilder_ == null) {
+        peerIdentity_ = null;
+      } else {
+        peerIdentity_ = null;
+        peerIdentityBuilder_ = null;
+      }
+      if (localIdentityBuilder_ == null) {
+        localIdentity_ = null;
+      } else {
+        localIdentity_ = null;
+        localIdentityBuilder_ = null;
+      }
+      keepChannelOpen_ = false;
+
+      if (peerRpcVersionsBuilder_ == null) {
+        peerRpcVersions_ = null;
+      } else {
+        peerRpcVersions_ = null;
+        peerRpcVersionsBuilder_ = null;
+      }
+      return this;
+    }
+
+    public com.google.protobuf.Descriptors.Descriptor
+        getDescriptorForType() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerResult_descriptor;
+    }
+
+    public io.grpc.alts.internal.HandshakerResult getDefaultInstanceForType() {
+      return io.grpc.alts.internal.HandshakerResult.getDefaultInstance();
+    }
+
+    public io.grpc.alts.internal.HandshakerResult build() {
+      io.grpc.alts.internal.HandshakerResult result = buildPartial();
+      if (!result.isInitialized()) {
+        throw newUninitializedMessageException(result);
+      }
+      return result;
+    }
+
+    public io.grpc.alts.internal.HandshakerResult buildPartial() {
+      io.grpc.alts.internal.HandshakerResult result = new io.grpc.alts.internal.HandshakerResult(this);
+      result.applicationProtocol_ = applicationProtocol_;
+      result.recordProtocol_ = recordProtocol_;
+      result.keyData_ = keyData_;
+      if (peerIdentityBuilder_ == null) {
+        result.peerIdentity_ = peerIdentity_;
+      } else {
+        result.peerIdentity_ = peerIdentityBuilder_.build();
+      }
+      if (localIdentityBuilder_ == null) {
+        result.localIdentity_ = localIdentity_;
+      } else {
+        result.localIdentity_ = localIdentityBuilder_.build();
+      }
+      result.keepChannelOpen_ = keepChannelOpen_;
+      if (peerRpcVersionsBuilder_ == null) {
+        result.peerRpcVersions_ = peerRpcVersions_;
+      } else {
+        result.peerRpcVersions_ = peerRpcVersionsBuilder_.build();
+      }
+      onBuilt();
+      return result;
+    }
+
+    public Builder clone() {
+      return (Builder) super.clone();
+    }
+    public Builder setField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.setField(field, value);
+    }
+    public Builder clearField(
+        com.google.protobuf.Descriptors.FieldDescriptor field) {
+      return (Builder) super.clearField(field);
+    }
+    public Builder clearOneof(
+        com.google.protobuf.Descriptors.OneofDescriptor oneof) {
+      return (Builder) super.clearOneof(oneof);
+    }
+    public Builder setRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        int index, java.lang.Object value) {
+      return (Builder) super.setRepeatedField(field, index, value);
+    }
+    public Builder addRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.addRepeatedField(field, value);
+    }
+    public Builder mergeFrom(com.google.protobuf.Message other) {
+      if (other instanceof io.grpc.alts.internal.HandshakerResult) {
+        return mergeFrom((io.grpc.alts.internal.HandshakerResult)other);
+      } else {
+        super.mergeFrom(other);
+        return this;
+      }
+    }
+
+    public Builder mergeFrom(io.grpc.alts.internal.HandshakerResult other) {
+      if (other == io.grpc.alts.internal.HandshakerResult.getDefaultInstance()) return this;
+      if (!other.getApplicationProtocol().isEmpty()) {
+        applicationProtocol_ = other.applicationProtocol_;
+        onChanged();
+      }
+      if (!other.getRecordProtocol().isEmpty()) {
+        recordProtocol_ = other.recordProtocol_;
+        onChanged();
+      }
+      if (other.getKeyData() != com.google.protobuf.ByteString.EMPTY) {
+        setKeyData(other.getKeyData());
+      }
+      if (other.hasPeerIdentity()) {
+        mergePeerIdentity(other.getPeerIdentity());
+      }
+      if (other.hasLocalIdentity()) {
+        mergeLocalIdentity(other.getLocalIdentity());
+      }
+      if (other.getKeepChannelOpen() != false) {
+        setKeepChannelOpen(other.getKeepChannelOpen());
+      }
+      if (other.hasPeerRpcVersions()) {
+        mergePeerRpcVersions(other.getPeerRpcVersions());
+      }
+      this.mergeUnknownFields(other.unknownFields);
+      onChanged();
+      return this;
+    }
+
+    public final boolean isInitialized() {
+      return true;
+    }
+
+    public Builder mergeFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      io.grpc.alts.internal.HandshakerResult parsedMessage = null;
+      try {
+        parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);
+      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+        parsedMessage = (io.grpc.alts.internal.HandshakerResult) e.getUnfinishedMessage();
+        throw e.unwrapIOException();
+      } finally {
+        if (parsedMessage != null) {
+          mergeFrom(parsedMessage);
+        }
+      }
+      return this;
+    }
+
+    private java.lang.Object applicationProtocol_ = "";
+    /**
+     * <pre>
+     * The application protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string application_protocol = 1;</code>
+     */
+    public java.lang.String getApplicationProtocol() {
+      java.lang.Object ref = applicationProtocol_;
+      if (!(ref instanceof java.lang.String)) {
+        com.google.protobuf.ByteString bs =
+            (com.google.protobuf.ByteString) ref;
+        java.lang.String s = bs.toStringUtf8();
+        applicationProtocol_ = s;
+        return s;
+      } else {
+        return (java.lang.String) ref;
+      }
+    }
+    /**
+     * <pre>
+     * The application protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string application_protocol = 1;</code>
+     */
+    public com.google.protobuf.ByteString
+        getApplicationProtocolBytes() {
+      java.lang.Object ref = applicationProtocol_;
+      if (ref instanceof String) {
+        com.google.protobuf.ByteString b = 
+            com.google.protobuf.ByteString.copyFromUtf8(
+                (java.lang.String) ref);
+        applicationProtocol_ = b;
+        return b;
+      } else {
+        return (com.google.protobuf.ByteString) ref;
+      }
+    }
+    /**
+     * <pre>
+     * The application protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string application_protocol = 1;</code>
+     */
+    public Builder setApplicationProtocol(
+        java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  
+      applicationProtocol_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The application protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string application_protocol = 1;</code>
+     */
+    public Builder clearApplicationProtocol() {
+      
+      applicationProtocol_ = getDefaultInstance().getApplicationProtocol();
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The application protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string application_protocol = 1;</code>
+     */
+    public Builder setApplicationProtocolBytes(
+        com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  checkByteStringIsUtf8(value);
+      
+      applicationProtocol_ = value;
+      onChanged();
+      return this;
+    }
+
+    private java.lang.Object recordProtocol_ = "";
+    /**
+     * <pre>
+     * The record protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string record_protocol = 2;</code>
+     */
+    public java.lang.String getRecordProtocol() {
+      java.lang.Object ref = recordProtocol_;
+      if (!(ref instanceof java.lang.String)) {
+        com.google.protobuf.ByteString bs =
+            (com.google.protobuf.ByteString) ref;
+        java.lang.String s = bs.toStringUtf8();
+        recordProtocol_ = s;
+        return s;
+      } else {
+        return (java.lang.String) ref;
+      }
+    }
+    /**
+     * <pre>
+     * The record protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string record_protocol = 2;</code>
+     */
+    public com.google.protobuf.ByteString
+        getRecordProtocolBytes() {
+      java.lang.Object ref = recordProtocol_;
+      if (ref instanceof String) {
+        com.google.protobuf.ByteString b = 
+            com.google.protobuf.ByteString.copyFromUtf8(
+                (java.lang.String) ref);
+        recordProtocol_ = b;
+        return b;
+      } else {
+        return (com.google.protobuf.ByteString) ref;
+      }
+    }
+    /**
+     * <pre>
+     * The record protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string record_protocol = 2;</code>
+     */
+    public Builder setRecordProtocol(
+        java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  
+      recordProtocol_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The record protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string record_protocol = 2;</code>
+     */
+    public Builder clearRecordProtocol() {
+      
+      recordProtocol_ = getDefaultInstance().getRecordProtocol();
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The record protocol negotiated for this connection.
+     * </pre>
+     *
+     * <code>string record_protocol = 2;</code>
+     */
+    public Builder setRecordProtocolBytes(
+        com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  checkByteStringIsUtf8(value);
+      
+      recordProtocol_ = value;
+      onChanged();
+      return this;
+    }
+
+    private com.google.protobuf.ByteString keyData_ = com.google.protobuf.ByteString.EMPTY;
+    /**
+     * <pre>
+     * Cryptographic key data. The key data may be more than the key length
+     * required for the record protocol, thus the client of the handshaker
+     * service needs to truncate the key data into the right key length.
+     * </pre>
+     *
+     * <code>bytes key_data = 3;</code>
+     */
+    public com.google.protobuf.ByteString getKeyData() {
+      return keyData_;
+    }
+    /**
+     * <pre>
+     * Cryptographic key data. The key data may be more than the key length
+     * required for the record protocol, thus the client of the handshaker
+     * service needs to truncate the key data into the right key length.
+     * </pre>
+     *
+     * <code>bytes key_data = 3;</code>
+     */
+    public Builder setKeyData(com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  
+      keyData_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * Cryptographic key data. The key data may be more than the key length
+     * required for the record protocol, thus the client of the handshaker
+     * service needs to truncate the key data into the right key length.
+     * </pre>
+     *
+     * <code>bytes key_data = 3;</code>
+     */
+    public Builder clearKeyData() {
+      
+      keyData_ = getDefaultInstance().getKeyData();
+      onChanged();
+      return this;
+    }
+
+    private io.grpc.alts.internal.Identity peerIdentity_ = null;
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.Identity, io.grpc.alts.internal.Identity.Builder, io.grpc.alts.internal.IdentityOrBuilder> peerIdentityBuilder_;
+    /**
+     * <pre>
+     * The authenticated identity of the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity peer_identity = 4;</code>
+     */
+    public boolean hasPeerIdentity() {
+      return peerIdentityBuilder_ != null || peerIdentity_ != null;
+    }
+    /**
+     * <pre>
+     * The authenticated identity of the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity peer_identity = 4;</code>
+     */
+    public io.grpc.alts.internal.Identity getPeerIdentity() {
+      if (peerIdentityBuilder_ == null) {
+        return peerIdentity_ == null ? io.grpc.alts.internal.Identity.getDefaultInstance() : peerIdentity_;
+      } else {
+        return peerIdentityBuilder_.getMessage();
+      }
+    }
+    /**
+     * <pre>
+     * The authenticated identity of the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity peer_identity = 4;</code>
+     */
+    public Builder setPeerIdentity(io.grpc.alts.internal.Identity value) {
+      if (peerIdentityBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        peerIdentity_ = value;
+        onChanged();
+      } else {
+        peerIdentityBuilder_.setMessage(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * The authenticated identity of the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity peer_identity = 4;</code>
+     */
+    public Builder setPeerIdentity(
+        io.grpc.alts.internal.Identity.Builder builderForValue) {
+      if (peerIdentityBuilder_ == null) {
+        peerIdentity_ = builderForValue.build();
+        onChanged();
+      } else {
+        peerIdentityBuilder_.setMessage(builderForValue.build());
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * The authenticated identity of the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity peer_identity = 4;</code>
+     */
+    public Builder mergePeerIdentity(io.grpc.alts.internal.Identity value) {
+      if (peerIdentityBuilder_ == null) {
+        if (peerIdentity_ != null) {
+          peerIdentity_ =
+            io.grpc.alts.internal.Identity.newBuilder(peerIdentity_).mergeFrom(value).buildPartial();
+        } else {
+          peerIdentity_ = value;
+        }
+        onChanged();
+      } else {
+        peerIdentityBuilder_.mergeFrom(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * The authenticated identity of the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity peer_identity = 4;</code>
+     */
+    public Builder clearPeerIdentity() {
+      if (peerIdentityBuilder_ == null) {
+        peerIdentity_ = null;
+        onChanged();
+      } else {
+        peerIdentity_ = null;
+        peerIdentityBuilder_ = null;
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * The authenticated identity of the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity peer_identity = 4;</code>
+     */
+    public io.grpc.alts.internal.Identity.Builder getPeerIdentityBuilder() {
+      
+      onChanged();
+      return getPeerIdentityFieldBuilder().getBuilder();
+    }
+    /**
+     * <pre>
+     * The authenticated identity of the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity peer_identity = 4;</code>
+     */
+    public io.grpc.alts.internal.IdentityOrBuilder getPeerIdentityOrBuilder() {
+      if (peerIdentityBuilder_ != null) {
+        return peerIdentityBuilder_.getMessageOrBuilder();
+      } else {
+        return peerIdentity_ == null ?
+            io.grpc.alts.internal.Identity.getDefaultInstance() : peerIdentity_;
+      }
+    }
+    /**
+     * <pre>
+     * The authenticated identity of the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity peer_identity = 4;</code>
+     */
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.Identity, io.grpc.alts.internal.Identity.Builder, io.grpc.alts.internal.IdentityOrBuilder> 
+        getPeerIdentityFieldBuilder() {
+      if (peerIdentityBuilder_ == null) {
+        peerIdentityBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
+            io.grpc.alts.internal.Identity, io.grpc.alts.internal.Identity.Builder, io.grpc.alts.internal.IdentityOrBuilder>(
+                getPeerIdentity(),
+                getParentForChildren(),
+                isClean());
+        peerIdentity_ = null;
+      }
+      return peerIdentityBuilder_;
+    }
+
+    private io.grpc.alts.internal.Identity localIdentity_ = null;
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.Identity, io.grpc.alts.internal.Identity.Builder, io.grpc.alts.internal.IdentityOrBuilder> localIdentityBuilder_;
+    /**
+     * <pre>
+     * The local identity used in the handshake.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity local_identity = 5;</code>
+     */
+    public boolean hasLocalIdentity() {
+      return localIdentityBuilder_ != null || localIdentity_ != null;
+    }
+    /**
+     * <pre>
+     * The local identity used in the handshake.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity local_identity = 5;</code>
+     */
+    public io.grpc.alts.internal.Identity getLocalIdentity() {
+      if (localIdentityBuilder_ == null) {
+        return localIdentity_ == null ? io.grpc.alts.internal.Identity.getDefaultInstance() : localIdentity_;
+      } else {
+        return localIdentityBuilder_.getMessage();
+      }
+    }
+    /**
+     * <pre>
+     * The local identity used in the handshake.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity local_identity = 5;</code>
+     */
+    public Builder setLocalIdentity(io.grpc.alts.internal.Identity value) {
+      if (localIdentityBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        localIdentity_ = value;
+        onChanged();
+      } else {
+        localIdentityBuilder_.setMessage(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * The local identity used in the handshake.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity local_identity = 5;</code>
+     */
+    public Builder setLocalIdentity(
+        io.grpc.alts.internal.Identity.Builder builderForValue) {
+      if (localIdentityBuilder_ == null) {
+        localIdentity_ = builderForValue.build();
+        onChanged();
+      } else {
+        localIdentityBuilder_.setMessage(builderForValue.build());
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * The local identity used in the handshake.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity local_identity = 5;</code>
+     */
+    public Builder mergeLocalIdentity(io.grpc.alts.internal.Identity value) {
+      if (localIdentityBuilder_ == null) {
+        if (localIdentity_ != null) {
+          localIdentity_ =
+            io.grpc.alts.internal.Identity.newBuilder(localIdentity_).mergeFrom(value).buildPartial();
+        } else {
+          localIdentity_ = value;
+        }
+        onChanged();
+      } else {
+        localIdentityBuilder_.mergeFrom(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * The local identity used in the handshake.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity local_identity = 5;</code>
+     */
+    public Builder clearLocalIdentity() {
+      if (localIdentityBuilder_ == null) {
+        localIdentity_ = null;
+        onChanged();
+      } else {
+        localIdentity_ = null;
+        localIdentityBuilder_ = null;
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * The local identity used in the handshake.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity local_identity = 5;</code>
+     */
+    public io.grpc.alts.internal.Identity.Builder getLocalIdentityBuilder() {
+      
+      onChanged();
+      return getLocalIdentityFieldBuilder().getBuilder();
+    }
+    /**
+     * <pre>
+     * The local identity used in the handshake.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity local_identity = 5;</code>
+     */
+    public io.grpc.alts.internal.IdentityOrBuilder getLocalIdentityOrBuilder() {
+      if (localIdentityBuilder_ != null) {
+        return localIdentityBuilder_.getMessageOrBuilder();
+      } else {
+        return localIdentity_ == null ?
+            io.grpc.alts.internal.Identity.getDefaultInstance() : localIdentity_;
+      }
+    }
+    /**
+     * <pre>
+     * The local identity used in the handshake.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity local_identity = 5;</code>
+     */
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.Identity, io.grpc.alts.internal.Identity.Builder, io.grpc.alts.internal.IdentityOrBuilder> 
+        getLocalIdentityFieldBuilder() {
+      if (localIdentityBuilder_ == null) {
+        localIdentityBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
+            io.grpc.alts.internal.Identity, io.grpc.alts.internal.Identity.Builder, io.grpc.alts.internal.IdentityOrBuilder>(
+                getLocalIdentity(),
+                getParentForChildren(),
+                isClean());
+        localIdentity_ = null;
+      }
+      return localIdentityBuilder_;
+    }
+
+    private boolean keepChannelOpen_ ;
+    /**
+     * <pre>
+     * Indicate whether the handshaker service client should keep the channel
+     * between the handshaker service open, e.g., in order to handle
+     * post-handshake messages in the future.
+     * </pre>
+     *
+     * <code>bool keep_channel_open = 6;</code>
+     */
+    public boolean getKeepChannelOpen() {
+      return keepChannelOpen_;
+    }
+    /**
+     * <pre>
+     * Indicate whether the handshaker service client should keep the channel
+     * between the handshaker service open, e.g., in order to handle
+     * post-handshake messages in the future.
+     * </pre>
+     *
+     * <code>bool keep_channel_open = 6;</code>
+     */
+    public Builder setKeepChannelOpen(boolean value) {
+      
+      keepChannelOpen_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * Indicate whether the handshaker service client should keep the channel
+     * between the handshaker service open, e.g., in order to handle
+     * post-handshake messages in the future.
+     * </pre>
+     *
+     * <code>bool keep_channel_open = 6;</code>
+     */
+    public Builder clearKeepChannelOpen() {
+      
+      keepChannelOpen_ = false;
+      onChanged();
+      return this;
+    }
+
+    private io.grpc.alts.internal.RpcProtocolVersions peerRpcVersions_ = null;
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.RpcProtocolVersions, io.grpc.alts.internal.RpcProtocolVersions.Builder, io.grpc.alts.internal.RpcProtocolVersionsOrBuilder> peerRpcVersionsBuilder_;
+    /**
+     * <pre>
+     * The RPC protocol versions supported by the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
+     */
+    public boolean hasPeerRpcVersions() {
+      return peerRpcVersionsBuilder_ != null || peerRpcVersions_ != null;
+    }
+    /**
+     * <pre>
+     * The RPC protocol versions supported by the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
+     */
+    public io.grpc.alts.internal.RpcProtocolVersions getPeerRpcVersions() {
+      if (peerRpcVersionsBuilder_ == null) {
+        return peerRpcVersions_ == null ? io.grpc.alts.internal.RpcProtocolVersions.getDefaultInstance() : peerRpcVersions_;
+      } else {
+        return peerRpcVersionsBuilder_.getMessage();
+      }
+    }
+    /**
+     * <pre>
+     * The RPC protocol versions supported by the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
+     */
+    public Builder setPeerRpcVersions(io.grpc.alts.internal.RpcProtocolVersions value) {
+      if (peerRpcVersionsBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        peerRpcVersions_ = value;
+        onChanged();
+      } else {
+        peerRpcVersionsBuilder_.setMessage(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * The RPC protocol versions supported by the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
+     */
+    public Builder setPeerRpcVersions(
+        io.grpc.alts.internal.RpcProtocolVersions.Builder builderForValue) {
+      if (peerRpcVersionsBuilder_ == null) {
+        peerRpcVersions_ = builderForValue.build();
+        onChanged();
+      } else {
+        peerRpcVersionsBuilder_.setMessage(builderForValue.build());
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * The RPC protocol versions supported by the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
+     */
+    public Builder mergePeerRpcVersions(io.grpc.alts.internal.RpcProtocolVersions value) {
+      if (peerRpcVersionsBuilder_ == null) {
+        if (peerRpcVersions_ != null) {
+          peerRpcVersions_ =
+            io.grpc.alts.internal.RpcProtocolVersions.newBuilder(peerRpcVersions_).mergeFrom(value).buildPartial();
+        } else {
+          peerRpcVersions_ = value;
+        }
+        onChanged();
+      } else {
+        peerRpcVersionsBuilder_.mergeFrom(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * The RPC protocol versions supported by the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
+     */
+    public Builder clearPeerRpcVersions() {
+      if (peerRpcVersionsBuilder_ == null) {
+        peerRpcVersions_ = null;
+        onChanged();
+      } else {
+        peerRpcVersions_ = null;
+        peerRpcVersionsBuilder_ = null;
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * The RPC protocol versions supported by the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
+     */
+    public io.grpc.alts.internal.RpcProtocolVersions.Builder getPeerRpcVersionsBuilder() {
+      
+      onChanged();
+      return getPeerRpcVersionsFieldBuilder().getBuilder();
+    }
+    /**
+     * <pre>
+     * The RPC protocol versions supported by the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
+     */
+    public io.grpc.alts.internal.RpcProtocolVersionsOrBuilder getPeerRpcVersionsOrBuilder() {
+      if (peerRpcVersionsBuilder_ != null) {
+        return peerRpcVersionsBuilder_.getMessageOrBuilder();
+      } else {
+        return peerRpcVersions_ == null ?
+            io.grpc.alts.internal.RpcProtocolVersions.getDefaultInstance() : peerRpcVersions_;
+      }
+    }
+    /**
+     * <pre>
+     * The RPC protocol versions supported by the peer.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
+     */
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.RpcProtocolVersions, io.grpc.alts.internal.RpcProtocolVersions.Builder, io.grpc.alts.internal.RpcProtocolVersionsOrBuilder> 
+        getPeerRpcVersionsFieldBuilder() {
+      if (peerRpcVersionsBuilder_ == null) {
+        peerRpcVersionsBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
+            io.grpc.alts.internal.RpcProtocolVersions, io.grpc.alts.internal.RpcProtocolVersions.Builder, io.grpc.alts.internal.RpcProtocolVersionsOrBuilder>(
+                getPeerRpcVersions(),
+                getParentForChildren(),
+                isClean());
+        peerRpcVersions_ = null;
+      }
+      return peerRpcVersionsBuilder_;
+    }
+    public final Builder setUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.setUnknownFieldsProto3(unknownFields);
+    }
+
+    public final Builder mergeUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.mergeUnknownFields(unknownFields);
+    }
+
+
+    // @@protoc_insertion_point(builder_scope:grpc.gcp.HandshakerResult)
+  }
+
+  // @@protoc_insertion_point(class_scope:grpc.gcp.HandshakerResult)
+  private static final io.grpc.alts.internal.HandshakerResult DEFAULT_INSTANCE;
+  static {
+    DEFAULT_INSTANCE = new io.grpc.alts.internal.HandshakerResult();
+  }
+
+  public static io.grpc.alts.internal.HandshakerResult getDefaultInstance() {
+    return DEFAULT_INSTANCE;
+  }
+
+  private static final com.google.protobuf.Parser<HandshakerResult>
+      PARSER = new com.google.protobuf.AbstractParser<HandshakerResult>() {
+    public HandshakerResult parsePartialFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return new HandshakerResult(input, extensionRegistry);
+    }
+  };
+
+  public static com.google.protobuf.Parser<HandshakerResult> parser() {
+    return PARSER;
+  }
+
+  @java.lang.Override
+  public com.google.protobuf.Parser<HandshakerResult> getParserForType() {
+    return PARSER;
+  }
+
+  public io.grpc.alts.internal.HandshakerResult getDefaultInstanceForType() {
+    return DEFAULT_INSTANCE;
+  }
+
+}
+
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerResultOrBuilder.java b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerResultOrBuilder.java
new file mode 100644
index 0000000000..fbf0f5d061
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerResultOrBuilder.java
@@ -0,0 +1,142 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+public interface HandshakerResultOrBuilder extends
+    // @@protoc_insertion_point(interface_extends:grpc.gcp.HandshakerResult)
+    com.google.protobuf.MessageOrBuilder {
+
+  /**
+   * <pre>
+   * The application protocol negotiated for this connection.
+   * </pre>
+   *
+   * <code>string application_protocol = 1;</code>
+   */
+  java.lang.String getApplicationProtocol();
+  /**
+   * <pre>
+   * The application protocol negotiated for this connection.
+   * </pre>
+   *
+   * <code>string application_protocol = 1;</code>
+   */
+  com.google.protobuf.ByteString
+      getApplicationProtocolBytes();
+
+  /**
+   * <pre>
+   * The record protocol negotiated for this connection.
+   * </pre>
+   *
+   * <code>string record_protocol = 2;</code>
+   */
+  java.lang.String getRecordProtocol();
+  /**
+   * <pre>
+   * The record protocol negotiated for this connection.
+   * </pre>
+   *
+   * <code>string record_protocol = 2;</code>
+   */
+  com.google.protobuf.ByteString
+      getRecordProtocolBytes();
+
+  /**
+   * <pre>
+   * Cryptographic key data. The key data may be more than the key length
+   * required for the record protocol, thus the client of the handshaker
+   * service needs to truncate the key data into the right key length.
+   * </pre>
+   *
+   * <code>bytes key_data = 3;</code>
+   */
+  com.google.protobuf.ByteString getKeyData();
+
+  /**
+   * <pre>
+   * The authenticated identity of the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Identity peer_identity = 4;</code>
+   */
+  boolean hasPeerIdentity();
+  /**
+   * <pre>
+   * The authenticated identity of the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Identity peer_identity = 4;</code>
+   */
+  io.grpc.alts.internal.Identity getPeerIdentity();
+  /**
+   * <pre>
+   * The authenticated identity of the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Identity peer_identity = 4;</code>
+   */
+  io.grpc.alts.internal.IdentityOrBuilder getPeerIdentityOrBuilder();
+
+  /**
+   * <pre>
+   * The local identity used in the handshake.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Identity local_identity = 5;</code>
+   */
+  boolean hasLocalIdentity();
+  /**
+   * <pre>
+   * The local identity used in the handshake.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Identity local_identity = 5;</code>
+   */
+  io.grpc.alts.internal.Identity getLocalIdentity();
+  /**
+   * <pre>
+   * The local identity used in the handshake.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Identity local_identity = 5;</code>
+   */
+  io.grpc.alts.internal.IdentityOrBuilder getLocalIdentityOrBuilder();
+
+  /**
+   * <pre>
+   * Indicate whether the handshaker service client should keep the channel
+   * between the handshaker service open, e.g., in order to handle
+   * post-handshake messages in the future.
+   * </pre>
+   *
+   * <code>bool keep_channel_open = 6;</code>
+   */
+  boolean getKeepChannelOpen();
+
+  /**
+   * <pre>
+   * The RPC protocol versions supported by the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
+   */
+  boolean hasPeerRpcVersions();
+  /**
+   * <pre>
+   * The RPC protocol versions supported by the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
+   */
+  io.grpc.alts.internal.RpcProtocolVersions getPeerRpcVersions();
+  /**
+   * <pre>
+   * The RPC protocol versions supported by the peer.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions peer_rpc_versions = 7;</code>
+   */
+  io.grpc.alts.internal.RpcProtocolVersionsOrBuilder getPeerRpcVersionsOrBuilder();
+}
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerStatus.java b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerStatus.java
new file mode 100644
index 0000000000..3fd497daf2
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerStatus.java
@@ -0,0 +1,618 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+/**
+ * Protobuf type {@code grpc.gcp.HandshakerStatus}
+ */
+public  final class HandshakerStatus extends
+    com.google.protobuf.GeneratedMessageV3 implements
+    // @@protoc_insertion_point(message_implements:grpc.gcp.HandshakerStatus)
+    HandshakerStatusOrBuilder {
+private static final long serialVersionUID = 0L;
+  // Use HandshakerStatus.newBuilder() to construct.
+  private HandshakerStatus(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
+    super(builder);
+  }
+  private HandshakerStatus() {
+    code_ = 0;
+    details_ = "";
+  }
+
+  @java.lang.Override
+  public final com.google.protobuf.UnknownFieldSet
+  getUnknownFields() {
+    return this.unknownFields;
+  }
+  private HandshakerStatus(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    this();
+    if (extensionRegistry == null) {
+      throw new java.lang.NullPointerException();
+    }
+    int mutable_bitField0_ = 0;
+    com.google.protobuf.UnknownFieldSet.Builder unknownFields =
+        com.google.protobuf.UnknownFieldSet.newBuilder();
+    try {
+      boolean done = false;
+      while (!done) {
+        int tag = input.readTag();
+        switch (tag) {
+          case 0:
+            done = true;
+            break;
+          default: {
+            if (!parseUnknownFieldProto3(
+                input, unknownFields, extensionRegistry, tag)) {
+              done = true;
+            }
+            break;
+          }
+          case 8: {
+
+            code_ = input.readUInt32();
+            break;
+          }
+          case 18: {
+            java.lang.String s = input.readStringRequireUtf8();
+
+            details_ = s;
+            break;
+          }
+        }
+      }
+    } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+      throw e.setUnfinishedMessage(this);
+    } catch (java.io.IOException e) {
+      throw new com.google.protobuf.InvalidProtocolBufferException(
+          e).setUnfinishedMessage(this);
+    } finally {
+      this.unknownFields = unknownFields.build();
+      makeExtensionsImmutable();
+    }
+  }
+  public static final com.google.protobuf.Descriptors.Descriptor
+      getDescriptor() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerStatus_descriptor;
+  }
+
+  protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internalGetFieldAccessorTable() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerStatus_fieldAccessorTable
+        .ensureFieldAccessorsInitialized(
+            io.grpc.alts.internal.HandshakerStatus.class, io.grpc.alts.internal.HandshakerStatus.Builder.class);
+  }
+
+  public static final int CODE_FIELD_NUMBER = 1;
+  private int code_;
+  /**
+   * <pre>
+   * The status code. This could be the gRPC status code.
+   * </pre>
+   *
+   * <code>uint32 code = 1;</code>
+   */
+  public int getCode() {
+    return code_;
+  }
+
+  public static final int DETAILS_FIELD_NUMBER = 2;
+  private volatile java.lang.Object details_;
+  /**
+   * <pre>
+   * The status details.
+   * </pre>
+   *
+   * <code>string details = 2;</code>
+   */
+  public java.lang.String getDetails() {
+    java.lang.Object ref = details_;
+    if (ref instanceof java.lang.String) {
+      return (java.lang.String) ref;
+    } else {
+      com.google.protobuf.ByteString bs = 
+          (com.google.protobuf.ByteString) ref;
+      java.lang.String s = bs.toStringUtf8();
+      details_ = s;
+      return s;
+    }
+  }
+  /**
+   * <pre>
+   * The status details.
+   * </pre>
+   *
+   * <code>string details = 2;</code>
+   */
+  public com.google.protobuf.ByteString
+      getDetailsBytes() {
+    java.lang.Object ref = details_;
+    if (ref instanceof java.lang.String) {
+      com.google.protobuf.ByteString b = 
+          com.google.protobuf.ByteString.copyFromUtf8(
+              (java.lang.String) ref);
+      details_ = b;
+      return b;
+    } else {
+      return (com.google.protobuf.ByteString) ref;
+    }
+  }
+
+  private byte memoizedIsInitialized = -1;
+  public final boolean isInitialized() {
+    byte isInitialized = memoizedIsInitialized;
+    if (isInitialized == 1) return true;
+    if (isInitialized == 0) return false;
+
+    memoizedIsInitialized = 1;
+    return true;
+  }
+
+  public void writeTo(com.google.protobuf.CodedOutputStream output)
+                      throws java.io.IOException {
+    if (code_ != 0) {
+      output.writeUInt32(1, code_);
+    }
+    if (!getDetailsBytes().isEmpty()) {
+      com.google.protobuf.GeneratedMessageV3.writeString(output, 2, details_);
+    }
+    unknownFields.writeTo(output);
+  }
+
+  public int getSerializedSize() {
+    int size = memoizedSize;
+    if (size != -1) return size;
+
+    size = 0;
+    if (code_ != 0) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeUInt32Size(1, code_);
+    }
+    if (!getDetailsBytes().isEmpty()) {
+      size += com.google.protobuf.GeneratedMessageV3.computeStringSize(2, details_);
+    }
+    size += unknownFields.getSerializedSize();
+    memoizedSize = size;
+    return size;
+  }
+
+  @java.lang.Override
+  public boolean equals(final java.lang.Object obj) {
+    if (obj == this) {
+     return true;
+    }
+    if (!(obj instanceof io.grpc.alts.internal.HandshakerStatus)) {
+      return super.equals(obj);
+    }
+    io.grpc.alts.internal.HandshakerStatus other = (io.grpc.alts.internal.HandshakerStatus) obj;
+
+    boolean result = true;
+    result = result && (getCode()
+        == other.getCode());
+    result = result && getDetails()
+        .equals(other.getDetails());
+    result = result && unknownFields.equals(other.unknownFields);
+    return result;
+  }
+
+  @java.lang.Override
+  public int hashCode() {
+    if (memoizedHashCode != 0) {
+      return memoizedHashCode;
+    }
+    int hash = 41;
+    hash = (19 * hash) + getDescriptor().hashCode();
+    hash = (37 * hash) + CODE_FIELD_NUMBER;
+    hash = (53 * hash) + getCode();
+    hash = (37 * hash) + DETAILS_FIELD_NUMBER;
+    hash = (53 * hash) + getDetails().hashCode();
+    hash = (29 * hash) + unknownFields.hashCode();
+    memoizedHashCode = hash;
+    return hash;
+  }
+
+  public static io.grpc.alts.internal.HandshakerStatus parseFrom(
+      java.nio.ByteBuffer data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.HandshakerStatus parseFrom(
+      java.nio.ByteBuffer data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerStatus parseFrom(
+      com.google.protobuf.ByteString data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.HandshakerStatus parseFrom(
+      com.google.protobuf.ByteString data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerStatus parseFrom(byte[] data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.HandshakerStatus parseFrom(
+      byte[] data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerStatus parseFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.HandshakerStatus parseFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerStatus parseDelimitedFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.HandshakerStatus parseDelimitedFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.HandshakerStatus parseFrom(
+      com.google.protobuf.CodedInputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.HandshakerStatus parseFrom(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+
+  public Builder newBuilderForType() { return newBuilder(); }
+  public static Builder newBuilder() {
+    return DEFAULT_INSTANCE.toBuilder();
+  }
+  public static Builder newBuilder(io.grpc.alts.internal.HandshakerStatus prototype) {
+    return DEFAULT_INSTANCE.toBuilder().mergeFrom(prototype);
+  }
+  public Builder toBuilder() {
+    return this == DEFAULT_INSTANCE
+        ? new Builder() : new Builder().mergeFrom(this);
+  }
+
+  @java.lang.Override
+  protected Builder newBuilderForType(
+      com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+    Builder builder = new Builder(parent);
+    return builder;
+  }
+  /**
+   * Protobuf type {@code grpc.gcp.HandshakerStatus}
+   */
+  public static final class Builder extends
+      com.google.protobuf.GeneratedMessageV3.Builder<Builder> implements
+      // @@protoc_insertion_point(builder_implements:grpc.gcp.HandshakerStatus)
+      io.grpc.alts.internal.HandshakerStatusOrBuilder {
+    public static final com.google.protobuf.Descriptors.Descriptor
+        getDescriptor() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerStatus_descriptor;
+    }
+
+    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+        internalGetFieldAccessorTable() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerStatus_fieldAccessorTable
+          .ensureFieldAccessorsInitialized(
+              io.grpc.alts.internal.HandshakerStatus.class, io.grpc.alts.internal.HandshakerStatus.Builder.class);
+    }
+
+    // Construct using io.grpc.alts.internal.HandshakerStatus.newBuilder()
+    private Builder() {
+      maybeForceBuilderInitialization();
+    }
+
+    private Builder(
+        com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+      super(parent);
+      maybeForceBuilderInitialization();
+    }
+    private void maybeForceBuilderInitialization() {
+      if (com.google.protobuf.GeneratedMessageV3
+              .alwaysUseFieldBuilders) {
+      }
+    }
+    public Builder clear() {
+      super.clear();
+      code_ = 0;
+
+      details_ = "";
+
+      return this;
+    }
+
+    public com.google.protobuf.Descriptors.Descriptor
+        getDescriptorForType() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_HandshakerStatus_descriptor;
+    }
+
+    public io.grpc.alts.internal.HandshakerStatus getDefaultInstanceForType() {
+      return io.grpc.alts.internal.HandshakerStatus.getDefaultInstance();
+    }
+
+    public io.grpc.alts.internal.HandshakerStatus build() {
+      io.grpc.alts.internal.HandshakerStatus result = buildPartial();
+      if (!result.isInitialized()) {
+        throw newUninitializedMessageException(result);
+      }
+      return result;
+    }
+
+    public io.grpc.alts.internal.HandshakerStatus buildPartial() {
+      io.grpc.alts.internal.HandshakerStatus result = new io.grpc.alts.internal.HandshakerStatus(this);
+      result.code_ = code_;
+      result.details_ = details_;
+      onBuilt();
+      return result;
+    }
+
+    public Builder clone() {
+      return (Builder) super.clone();
+    }
+    public Builder setField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.setField(field, value);
+    }
+    public Builder clearField(
+        com.google.protobuf.Descriptors.FieldDescriptor field) {
+      return (Builder) super.clearField(field);
+    }
+    public Builder clearOneof(
+        com.google.protobuf.Descriptors.OneofDescriptor oneof) {
+      return (Builder) super.clearOneof(oneof);
+    }
+    public Builder setRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        int index, java.lang.Object value) {
+      return (Builder) super.setRepeatedField(field, index, value);
+    }
+    public Builder addRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.addRepeatedField(field, value);
+    }
+    public Builder mergeFrom(com.google.protobuf.Message other) {
+      if (other instanceof io.grpc.alts.internal.HandshakerStatus) {
+        return mergeFrom((io.grpc.alts.internal.HandshakerStatus)other);
+      } else {
+        super.mergeFrom(other);
+        return this;
+      }
+    }
+
+    public Builder mergeFrom(io.grpc.alts.internal.HandshakerStatus other) {
+      if (other == io.grpc.alts.internal.HandshakerStatus.getDefaultInstance()) return this;
+      if (other.getCode() != 0) {
+        setCode(other.getCode());
+      }
+      if (!other.getDetails().isEmpty()) {
+        details_ = other.details_;
+        onChanged();
+      }
+      this.mergeUnknownFields(other.unknownFields);
+      onChanged();
+      return this;
+    }
+
+    public final boolean isInitialized() {
+      return true;
+    }
+
+    public Builder mergeFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      io.grpc.alts.internal.HandshakerStatus parsedMessage = null;
+      try {
+        parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);
+      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+        parsedMessage = (io.grpc.alts.internal.HandshakerStatus) e.getUnfinishedMessage();
+        throw e.unwrapIOException();
+      } finally {
+        if (parsedMessage != null) {
+          mergeFrom(parsedMessage);
+        }
+      }
+      return this;
+    }
+
+    private int code_ ;
+    /**
+     * <pre>
+     * The status code. This could be the gRPC status code.
+     * </pre>
+     *
+     * <code>uint32 code = 1;</code>
+     */
+    public int getCode() {
+      return code_;
+    }
+    /**
+     * <pre>
+     * The status code. This could be the gRPC status code.
+     * </pre>
+     *
+     * <code>uint32 code = 1;</code>
+     */
+    public Builder setCode(int value) {
+      
+      code_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The status code. This could be the gRPC status code.
+     * </pre>
+     *
+     * <code>uint32 code = 1;</code>
+     */
+    public Builder clearCode() {
+      
+      code_ = 0;
+      onChanged();
+      return this;
+    }
+
+    private java.lang.Object details_ = "";
+    /**
+     * <pre>
+     * The status details.
+     * </pre>
+     *
+     * <code>string details = 2;</code>
+     */
+    public java.lang.String getDetails() {
+      java.lang.Object ref = details_;
+      if (!(ref instanceof java.lang.String)) {
+        com.google.protobuf.ByteString bs =
+            (com.google.protobuf.ByteString) ref;
+        java.lang.String s = bs.toStringUtf8();
+        details_ = s;
+        return s;
+      } else {
+        return (java.lang.String) ref;
+      }
+    }
+    /**
+     * <pre>
+     * The status details.
+     * </pre>
+     *
+     * <code>string details = 2;</code>
+     */
+    public com.google.protobuf.ByteString
+        getDetailsBytes() {
+      java.lang.Object ref = details_;
+      if (ref instanceof String) {
+        com.google.protobuf.ByteString b = 
+            com.google.protobuf.ByteString.copyFromUtf8(
+                (java.lang.String) ref);
+        details_ = b;
+        return b;
+      } else {
+        return (com.google.protobuf.ByteString) ref;
+      }
+    }
+    /**
+     * <pre>
+     * The status details.
+     * </pre>
+     *
+     * <code>string details = 2;</code>
+     */
+    public Builder setDetails(
+        java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  
+      details_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The status details.
+     * </pre>
+     *
+     * <code>string details = 2;</code>
+     */
+    public Builder clearDetails() {
+      
+      details_ = getDefaultInstance().getDetails();
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The status details.
+     * </pre>
+     *
+     * <code>string details = 2;</code>
+     */
+    public Builder setDetailsBytes(
+        com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  checkByteStringIsUtf8(value);
+      
+      details_ = value;
+      onChanged();
+      return this;
+    }
+    public final Builder setUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.setUnknownFieldsProto3(unknownFields);
+    }
+
+    public final Builder mergeUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.mergeUnknownFields(unknownFields);
+    }
+
+
+    // @@protoc_insertion_point(builder_scope:grpc.gcp.HandshakerStatus)
+  }
+
+  // @@protoc_insertion_point(class_scope:grpc.gcp.HandshakerStatus)
+  private static final io.grpc.alts.internal.HandshakerStatus DEFAULT_INSTANCE;
+  static {
+    DEFAULT_INSTANCE = new io.grpc.alts.internal.HandshakerStatus();
+  }
+
+  public static io.grpc.alts.internal.HandshakerStatus getDefaultInstance() {
+    return DEFAULT_INSTANCE;
+  }
+
+  private static final com.google.protobuf.Parser<HandshakerStatus>
+      PARSER = new com.google.protobuf.AbstractParser<HandshakerStatus>() {
+    public HandshakerStatus parsePartialFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return new HandshakerStatus(input, extensionRegistry);
+    }
+  };
+
+  public static com.google.protobuf.Parser<HandshakerStatus> parser() {
+    return PARSER;
+  }
+
+  @java.lang.Override
+  public com.google.protobuf.Parser<HandshakerStatus> getParserForType() {
+    return PARSER;
+  }
+
+  public io.grpc.alts.internal.HandshakerStatus getDefaultInstanceForType() {
+    return DEFAULT_INSTANCE;
+  }
+
+}
+
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerStatusOrBuilder.java b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerStatusOrBuilder.java
new file mode 100644
index 0000000000..0ac69753fe
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/HandshakerStatusOrBuilder.java
@@ -0,0 +1,36 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+public interface HandshakerStatusOrBuilder extends
+    // @@protoc_insertion_point(interface_extends:grpc.gcp.HandshakerStatus)
+    com.google.protobuf.MessageOrBuilder {
+
+  /**
+   * <pre>
+   * The status code. This could be the gRPC status code.
+   * </pre>
+   *
+   * <code>uint32 code = 1;</code>
+   */
+  int getCode();
+
+  /**
+   * <pre>
+   * The status details.
+   * </pre>
+   *
+   * <code>string details = 2;</code>
+   */
+  java.lang.String getDetails();
+  /**
+   * <pre>
+   * The status details.
+   * </pre>
+   *
+   * <code>string details = 2;</code>
+   */
+  com.google.protobuf.ByteString
+      getDetailsBytes();
+}
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/Identity.java b/alts/src/generated/main/java/io/grpc/alts/internal/Identity.java
new file mode 100644
index 0000000000..235bb3366a
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/Identity.java
@@ -0,0 +1,1142 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+/**
+ * Protobuf type {@code grpc.gcp.Identity}
+ */
+public  final class Identity extends
+    com.google.protobuf.GeneratedMessageV3 implements
+    // @@protoc_insertion_point(message_implements:grpc.gcp.Identity)
+    IdentityOrBuilder {
+private static final long serialVersionUID = 0L;
+  // Use Identity.newBuilder() to construct.
+  private Identity(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
+    super(builder);
+  }
+  private Identity() {
+  }
+
+  @java.lang.Override
+  public final com.google.protobuf.UnknownFieldSet
+  getUnknownFields() {
+    return this.unknownFields;
+  }
+  private Identity(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    this();
+    if (extensionRegistry == null) {
+      throw new java.lang.NullPointerException();
+    }
+    int mutable_bitField0_ = 0;
+    com.google.protobuf.UnknownFieldSet.Builder unknownFields =
+        com.google.protobuf.UnknownFieldSet.newBuilder();
+    try {
+      boolean done = false;
+      while (!done) {
+        int tag = input.readTag();
+        switch (tag) {
+          case 0:
+            done = true;
+            break;
+          default: {
+            if (!parseUnknownFieldProto3(
+                input, unknownFields, extensionRegistry, tag)) {
+              done = true;
+            }
+            break;
+          }
+          case 10: {
+            java.lang.String s = input.readStringRequireUtf8();
+            identityOneofCase_ = 1;
+            identityOneof_ = s;
+            break;
+          }
+          case 18: {
+            java.lang.String s = input.readStringRequireUtf8();
+            identityOneofCase_ = 2;
+            identityOneof_ = s;
+            break;
+          }
+          case 26: {
+            if (!((mutable_bitField0_ & 0x00000004) == 0x00000004)) {
+              attributes_ = com.google.protobuf.MapField.newMapField(
+                  AttributesDefaultEntryHolder.defaultEntry);
+              mutable_bitField0_ |= 0x00000004;
+            }
+            com.google.protobuf.MapEntry<java.lang.String, java.lang.String>
+            attributes__ = input.readMessage(
+                AttributesDefaultEntryHolder.defaultEntry.getParserForType(), extensionRegistry);
+            attributes_.getMutableMap().put(
+                attributes__.getKey(), attributes__.getValue());
+            break;
+          }
+        }
+      }
+    } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+      throw e.setUnfinishedMessage(this);
+    } catch (java.io.IOException e) {
+      throw new com.google.protobuf.InvalidProtocolBufferException(
+          e).setUnfinishedMessage(this);
+    } finally {
+      this.unknownFields = unknownFields.build();
+      makeExtensionsImmutable();
+    }
+  }
+  public static final com.google.protobuf.Descriptors.Descriptor
+      getDescriptor() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_Identity_descriptor;
+  }
+
+  @SuppressWarnings({"rawtypes"})
+  protected com.google.protobuf.MapField internalGetMapField(
+      int number) {
+    switch (number) {
+      case 3:
+        return internalGetAttributes();
+      default:
+        throw new RuntimeException(
+            "Invalid map field number: " + number);
+    }
+  }
+  protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internalGetFieldAccessorTable() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_Identity_fieldAccessorTable
+        .ensureFieldAccessorsInitialized(
+            io.grpc.alts.internal.Identity.class, io.grpc.alts.internal.Identity.Builder.class);
+  }
+
+  private int bitField0_;
+  private int identityOneofCase_ = 0;
+  private java.lang.Object identityOneof_;
+  public enum IdentityOneofCase
+      implements com.google.protobuf.Internal.EnumLite {
+    SERVICE_ACCOUNT(1),
+    HOSTNAME(2),
+    IDENTITYONEOF_NOT_SET(0);
+    private final int value;
+    private IdentityOneofCase(int value) {
+      this.value = value;
+    }
+    /**
+     * @deprecated Use {@link #forNumber(int)} instead.
+     */
+    @java.lang.Deprecated
+    public static IdentityOneofCase valueOf(int value) {
+      return forNumber(value);
+    }
+
+    public static IdentityOneofCase forNumber(int value) {
+      switch (value) {
+        case 1: return SERVICE_ACCOUNT;
+        case 2: return HOSTNAME;
+        case 0: return IDENTITYONEOF_NOT_SET;
+        default: return null;
+      }
+    }
+    public int getNumber() {
+      return this.value;
+    }
+  };
+
+  public IdentityOneofCase
+  getIdentityOneofCase() {
+    return IdentityOneofCase.forNumber(
+        identityOneofCase_);
+  }
+
+  public static final int SERVICE_ACCOUNT_FIELD_NUMBER = 1;
+  /**
+   * <pre>
+   * Service account of a connection endpoint.
+   * </pre>
+   *
+   * <code>string service_account = 1;</code>
+   */
+  public java.lang.String getServiceAccount() {
+    java.lang.Object ref = "";
+    if (identityOneofCase_ == 1) {
+      ref = identityOneof_;
+    }
+    if (ref instanceof java.lang.String) {
+      return (java.lang.String) ref;
+    } else {
+      com.google.protobuf.ByteString bs = 
+          (com.google.protobuf.ByteString) ref;
+      java.lang.String s = bs.toStringUtf8();
+      if (identityOneofCase_ == 1) {
+        identityOneof_ = s;
+      }
+      return s;
+    }
+  }
+  /**
+   * <pre>
+   * Service account of a connection endpoint.
+   * </pre>
+   *
+   * <code>string service_account = 1;</code>
+   */
+  public com.google.protobuf.ByteString
+      getServiceAccountBytes() {
+    java.lang.Object ref = "";
+    if (identityOneofCase_ == 1) {
+      ref = identityOneof_;
+    }
+    if (ref instanceof java.lang.String) {
+      com.google.protobuf.ByteString b = 
+          com.google.protobuf.ByteString.copyFromUtf8(
+              (java.lang.String) ref);
+      if (identityOneofCase_ == 1) {
+        identityOneof_ = b;
+      }
+      return b;
+    } else {
+      return (com.google.protobuf.ByteString) ref;
+    }
+  }
+
+  public static final int HOSTNAME_FIELD_NUMBER = 2;
+  /**
+   * <pre>
+   * Hostname of a connection endpoint.
+   * </pre>
+   *
+   * <code>string hostname = 2;</code>
+   */
+  public java.lang.String getHostname() {
+    java.lang.Object ref = "";
+    if (identityOneofCase_ == 2) {
+      ref = identityOneof_;
+    }
+    if (ref instanceof java.lang.String) {
+      return (java.lang.String) ref;
+    } else {
+      com.google.protobuf.ByteString bs = 
+          (com.google.protobuf.ByteString) ref;
+      java.lang.String s = bs.toStringUtf8();
+      if (identityOneofCase_ == 2) {
+        identityOneof_ = s;
+      }
+      return s;
+    }
+  }
+  /**
+   * <pre>
+   * Hostname of a connection endpoint.
+   * </pre>
+   *
+   * <code>string hostname = 2;</code>
+   */
+  public com.google.protobuf.ByteString
+      getHostnameBytes() {
+    java.lang.Object ref = "";
+    if (identityOneofCase_ == 2) {
+      ref = identityOneof_;
+    }
+    if (ref instanceof java.lang.String) {
+      com.google.protobuf.ByteString b = 
+          com.google.protobuf.ByteString.copyFromUtf8(
+              (java.lang.String) ref);
+      if (identityOneofCase_ == 2) {
+        identityOneof_ = b;
+      }
+      return b;
+    } else {
+      return (com.google.protobuf.ByteString) ref;
+    }
+  }
+
+  public static final int ATTRIBUTES_FIELD_NUMBER = 3;
+  private static final class AttributesDefaultEntryHolder {
+    static final com.google.protobuf.MapEntry<
+        java.lang.String, java.lang.String> defaultEntry =
+            com.google.protobuf.MapEntry
+            .<java.lang.String, java.lang.String>newDefaultInstance(
+                io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_Identity_AttributesEntry_descriptor, 
+                com.google.protobuf.WireFormat.FieldType.STRING,
+                "",
+                com.google.protobuf.WireFormat.FieldType.STRING,
+                "");
+  }
+  private com.google.protobuf.MapField<
+      java.lang.String, java.lang.String> attributes_;
+  private com.google.protobuf.MapField<java.lang.String, java.lang.String>
+  internalGetAttributes() {
+    if (attributes_ == null) {
+      return com.google.protobuf.MapField.emptyMapField(
+          AttributesDefaultEntryHolder.defaultEntry);
+    }
+    return attributes_;
+  }
+
+  public int getAttributesCount() {
+    return internalGetAttributes().getMap().size();
+  }
+  /**
+   * <pre>
+   * Additional attributes of the identity.
+   * </pre>
+   *
+   * <code>map&lt;string, string&gt; attributes = 3;</code>
+   */
+
+  public boolean containsAttributes(
+      java.lang.String key) {
+    if (key == null) { throw new java.lang.NullPointerException(); }
+    return internalGetAttributes().getMap().containsKey(key);
+  }
+  /**
+   * Use {@link #getAttributesMap()} instead.
+   */
+  @java.lang.Deprecated
+  public java.util.Map<java.lang.String, java.lang.String> getAttributes() {
+    return getAttributesMap();
+  }
+  /**
+   * <pre>
+   * Additional attributes of the identity.
+   * </pre>
+   *
+   * <code>map&lt;string, string&gt; attributes = 3;</code>
+   */
+
+  public java.util.Map<java.lang.String, java.lang.String> getAttributesMap() {
+    return internalGetAttributes().getMap();
+  }
+  /**
+   * <pre>
+   * Additional attributes of the identity.
+   * </pre>
+   *
+   * <code>map&lt;string, string&gt; attributes = 3;</code>
+   */
+
+  public java.lang.String getAttributesOrDefault(
+      java.lang.String key,
+      java.lang.String defaultValue) {
+    if (key == null) { throw new java.lang.NullPointerException(); }
+    java.util.Map<java.lang.String, java.lang.String> map =
+        internalGetAttributes().getMap();
+    return map.containsKey(key) ? map.get(key) : defaultValue;
+  }
+  /**
+   * <pre>
+   * Additional attributes of the identity.
+   * </pre>
+   *
+   * <code>map&lt;string, string&gt; attributes = 3;</code>
+   */
+
+  public java.lang.String getAttributesOrThrow(
+      java.lang.String key) {
+    if (key == null) { throw new java.lang.NullPointerException(); }
+    java.util.Map<java.lang.String, java.lang.String> map =
+        internalGetAttributes().getMap();
+    if (!map.containsKey(key)) {
+      throw new java.lang.IllegalArgumentException();
+    }
+    return map.get(key);
+  }
+
+  private byte memoizedIsInitialized = -1;
+  public final boolean isInitialized() {
+    byte isInitialized = memoizedIsInitialized;
+    if (isInitialized == 1) return true;
+    if (isInitialized == 0) return false;
+
+    memoizedIsInitialized = 1;
+    return true;
+  }
+
+  public void writeTo(com.google.protobuf.CodedOutputStream output)
+                      throws java.io.IOException {
+    if (identityOneofCase_ == 1) {
+      com.google.protobuf.GeneratedMessageV3.writeString(output, 1, identityOneof_);
+    }
+    if (identityOneofCase_ == 2) {
+      com.google.protobuf.GeneratedMessageV3.writeString(output, 2, identityOneof_);
+    }
+    com.google.protobuf.GeneratedMessageV3
+      .serializeStringMapTo(
+        output,
+        internalGetAttributes(),
+        AttributesDefaultEntryHolder.defaultEntry,
+        3);
+    unknownFields.writeTo(output);
+  }
+
+  public int getSerializedSize() {
+    int size = memoizedSize;
+    if (size != -1) return size;
+
+    size = 0;
+    if (identityOneofCase_ == 1) {
+      size += com.google.protobuf.GeneratedMessageV3.computeStringSize(1, identityOneof_);
+    }
+    if (identityOneofCase_ == 2) {
+      size += com.google.protobuf.GeneratedMessageV3.computeStringSize(2, identityOneof_);
+    }
+    for (java.util.Map.Entry<java.lang.String, java.lang.String> entry
+         : internalGetAttributes().getMap().entrySet()) {
+      com.google.protobuf.MapEntry<java.lang.String, java.lang.String>
+      attributes__ = AttributesDefaultEntryHolder.defaultEntry.newBuilderForType()
+          .setKey(entry.getKey())
+          .setValue(entry.getValue())
+          .build();
+      size += com.google.protobuf.CodedOutputStream
+          .computeMessageSize(3, attributes__);
+    }
+    size += unknownFields.getSerializedSize();
+    memoizedSize = size;
+    return size;
+  }
+
+  @java.lang.Override
+  public boolean equals(final java.lang.Object obj) {
+    if (obj == this) {
+     return true;
+    }
+    if (!(obj instanceof io.grpc.alts.internal.Identity)) {
+      return super.equals(obj);
+    }
+    io.grpc.alts.internal.Identity other = (io.grpc.alts.internal.Identity) obj;
+
+    boolean result = true;
+    result = result && internalGetAttributes().equals(
+        other.internalGetAttributes());
+    result = result && getIdentityOneofCase().equals(
+        other.getIdentityOneofCase());
+    if (!result) return false;
+    switch (identityOneofCase_) {
+      case 1:
+        result = result && getServiceAccount()
+            .equals(other.getServiceAccount());
+        break;
+      case 2:
+        result = result && getHostname()
+            .equals(other.getHostname());
+        break;
+      case 0:
+      default:
+    }
+    result = result && unknownFields.equals(other.unknownFields);
+    return result;
+  }
+
+  @java.lang.Override
+  public int hashCode() {
+    if (memoizedHashCode != 0) {
+      return memoizedHashCode;
+    }
+    int hash = 41;
+    hash = (19 * hash) + getDescriptor().hashCode();
+    if (!internalGetAttributes().getMap().isEmpty()) {
+      hash = (37 * hash) + ATTRIBUTES_FIELD_NUMBER;
+      hash = (53 * hash) + internalGetAttributes().hashCode();
+    }
+    switch (identityOneofCase_) {
+      case 1:
+        hash = (37 * hash) + SERVICE_ACCOUNT_FIELD_NUMBER;
+        hash = (53 * hash) + getServiceAccount().hashCode();
+        break;
+      case 2:
+        hash = (37 * hash) + HOSTNAME_FIELD_NUMBER;
+        hash = (53 * hash) + getHostname().hashCode();
+        break;
+      case 0:
+      default:
+    }
+    hash = (29 * hash) + unknownFields.hashCode();
+    memoizedHashCode = hash;
+    return hash;
+  }
+
+  public static io.grpc.alts.internal.Identity parseFrom(
+      java.nio.ByteBuffer data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.Identity parseFrom(
+      java.nio.ByteBuffer data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.Identity parseFrom(
+      com.google.protobuf.ByteString data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.Identity parseFrom(
+      com.google.protobuf.ByteString data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.Identity parseFrom(byte[] data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.Identity parseFrom(
+      byte[] data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.Identity parseFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.Identity parseFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.Identity parseDelimitedFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.Identity parseDelimitedFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.Identity parseFrom(
+      com.google.protobuf.CodedInputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.Identity parseFrom(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+
+  public Builder newBuilderForType() { return newBuilder(); }
+  public static Builder newBuilder() {
+    return DEFAULT_INSTANCE.toBuilder();
+  }
+  public static Builder newBuilder(io.grpc.alts.internal.Identity prototype) {
+    return DEFAULT_INSTANCE.toBuilder().mergeFrom(prototype);
+  }
+  public Builder toBuilder() {
+    return this == DEFAULT_INSTANCE
+        ? new Builder() : new Builder().mergeFrom(this);
+  }
+
+  @java.lang.Override
+  protected Builder newBuilderForType(
+      com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+    Builder builder = new Builder(parent);
+    return builder;
+  }
+  /**
+   * Protobuf type {@code grpc.gcp.Identity}
+   */
+  public static final class Builder extends
+      com.google.protobuf.GeneratedMessageV3.Builder<Builder> implements
+      // @@protoc_insertion_point(builder_implements:grpc.gcp.Identity)
+      io.grpc.alts.internal.IdentityOrBuilder {
+    public static final com.google.protobuf.Descriptors.Descriptor
+        getDescriptor() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_Identity_descriptor;
+    }
+
+    @SuppressWarnings({"rawtypes"})
+    protected com.google.protobuf.MapField internalGetMapField(
+        int number) {
+      switch (number) {
+        case 3:
+          return internalGetAttributes();
+        default:
+          throw new RuntimeException(
+              "Invalid map field number: " + number);
+      }
+    }
+    @SuppressWarnings({"rawtypes"})
+    protected com.google.protobuf.MapField internalGetMutableMapField(
+        int number) {
+      switch (number) {
+        case 3:
+          return internalGetMutableAttributes();
+        default:
+          throw new RuntimeException(
+              "Invalid map field number: " + number);
+      }
+    }
+    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+        internalGetFieldAccessorTable() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_Identity_fieldAccessorTable
+          .ensureFieldAccessorsInitialized(
+              io.grpc.alts.internal.Identity.class, io.grpc.alts.internal.Identity.Builder.class);
+    }
+
+    // Construct using io.grpc.alts.internal.Identity.newBuilder()
+    private Builder() {
+      maybeForceBuilderInitialization();
+    }
+
+    private Builder(
+        com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+      super(parent);
+      maybeForceBuilderInitialization();
+    }
+    private void maybeForceBuilderInitialization() {
+      if (com.google.protobuf.GeneratedMessageV3
+              .alwaysUseFieldBuilders) {
+      }
+    }
+    public Builder clear() {
+      super.clear();
+      internalGetMutableAttributes().clear();
+      identityOneofCase_ = 0;
+      identityOneof_ = null;
+      return this;
+    }
+
+    public com.google.protobuf.Descriptors.Descriptor
+        getDescriptorForType() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_Identity_descriptor;
+    }
+
+    public io.grpc.alts.internal.Identity getDefaultInstanceForType() {
+      return io.grpc.alts.internal.Identity.getDefaultInstance();
+    }
+
+    public io.grpc.alts.internal.Identity build() {
+      io.grpc.alts.internal.Identity result = buildPartial();
+      if (!result.isInitialized()) {
+        throw newUninitializedMessageException(result);
+      }
+      return result;
+    }
+
+    public io.grpc.alts.internal.Identity buildPartial() {
+      io.grpc.alts.internal.Identity result = new io.grpc.alts.internal.Identity(this);
+      int from_bitField0_ = bitField0_;
+      int to_bitField0_ = 0;
+      if (identityOneofCase_ == 1) {
+        result.identityOneof_ = identityOneof_;
+      }
+      if (identityOneofCase_ == 2) {
+        result.identityOneof_ = identityOneof_;
+      }
+      result.attributes_ = internalGetAttributes();
+      result.attributes_.makeImmutable();
+      result.bitField0_ = to_bitField0_;
+      result.identityOneofCase_ = identityOneofCase_;
+      onBuilt();
+      return result;
+    }
+
+    public Builder clone() {
+      return (Builder) super.clone();
+    }
+    public Builder setField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.setField(field, value);
+    }
+    public Builder clearField(
+        com.google.protobuf.Descriptors.FieldDescriptor field) {
+      return (Builder) super.clearField(field);
+    }
+    public Builder clearOneof(
+        com.google.protobuf.Descriptors.OneofDescriptor oneof) {
+      return (Builder) super.clearOneof(oneof);
+    }
+    public Builder setRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        int index, java.lang.Object value) {
+      return (Builder) super.setRepeatedField(field, index, value);
+    }
+    public Builder addRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.addRepeatedField(field, value);
+    }
+    public Builder mergeFrom(com.google.protobuf.Message other) {
+      if (other instanceof io.grpc.alts.internal.Identity) {
+        return mergeFrom((io.grpc.alts.internal.Identity)other);
+      } else {
+        super.mergeFrom(other);
+        return this;
+      }
+    }
+
+    public Builder mergeFrom(io.grpc.alts.internal.Identity other) {
+      if (other == io.grpc.alts.internal.Identity.getDefaultInstance()) return this;
+      internalGetMutableAttributes().mergeFrom(
+          other.internalGetAttributes());
+      switch (other.getIdentityOneofCase()) {
+        case SERVICE_ACCOUNT: {
+          identityOneofCase_ = 1;
+          identityOneof_ = other.identityOneof_;
+          onChanged();
+          break;
+        }
+        case HOSTNAME: {
+          identityOneofCase_ = 2;
+          identityOneof_ = other.identityOneof_;
+          onChanged();
+          break;
+        }
+        case IDENTITYONEOF_NOT_SET: {
+          break;
+        }
+      }
+      this.mergeUnknownFields(other.unknownFields);
+      onChanged();
+      return this;
+    }
+
+    public final boolean isInitialized() {
+      return true;
+    }
+
+    public Builder mergeFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      io.grpc.alts.internal.Identity parsedMessage = null;
+      try {
+        parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);
+      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+        parsedMessage = (io.grpc.alts.internal.Identity) e.getUnfinishedMessage();
+        throw e.unwrapIOException();
+      } finally {
+        if (parsedMessage != null) {
+          mergeFrom(parsedMessage);
+        }
+      }
+      return this;
+    }
+    private int identityOneofCase_ = 0;
+    private java.lang.Object identityOneof_;
+    public IdentityOneofCase
+        getIdentityOneofCase() {
+      return IdentityOneofCase.forNumber(
+          identityOneofCase_);
+    }
+
+    public Builder clearIdentityOneof() {
+      identityOneofCase_ = 0;
+      identityOneof_ = null;
+      onChanged();
+      return this;
+    }
+
+    private int bitField0_;
+
+    /**
+     * <pre>
+     * Service account of a connection endpoint.
+     * </pre>
+     *
+     * <code>string service_account = 1;</code>
+     */
+    public java.lang.String getServiceAccount() {
+      java.lang.Object ref = "";
+      if (identityOneofCase_ == 1) {
+        ref = identityOneof_;
+      }
+      if (!(ref instanceof java.lang.String)) {
+        com.google.protobuf.ByteString bs =
+            (com.google.protobuf.ByteString) ref;
+        java.lang.String s = bs.toStringUtf8();
+        if (identityOneofCase_ == 1) {
+          identityOneof_ = s;
+        }
+        return s;
+      } else {
+        return (java.lang.String) ref;
+      }
+    }
+    /**
+     * <pre>
+     * Service account of a connection endpoint.
+     * </pre>
+     *
+     * <code>string service_account = 1;</code>
+     */
+    public com.google.protobuf.ByteString
+        getServiceAccountBytes() {
+      java.lang.Object ref = "";
+      if (identityOneofCase_ == 1) {
+        ref = identityOneof_;
+      }
+      if (ref instanceof String) {
+        com.google.protobuf.ByteString b = 
+            com.google.protobuf.ByteString.copyFromUtf8(
+                (java.lang.String) ref);
+        if (identityOneofCase_ == 1) {
+          identityOneof_ = b;
+        }
+        return b;
+      } else {
+        return (com.google.protobuf.ByteString) ref;
+      }
+    }
+    /**
+     * <pre>
+     * Service account of a connection endpoint.
+     * </pre>
+     *
+     * <code>string service_account = 1;</code>
+     */
+    public Builder setServiceAccount(
+        java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  identityOneofCase_ = 1;
+      identityOneof_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * Service account of a connection endpoint.
+     * </pre>
+     *
+     * <code>string service_account = 1;</code>
+     */
+    public Builder clearServiceAccount() {
+      if (identityOneofCase_ == 1) {
+        identityOneofCase_ = 0;
+        identityOneof_ = null;
+        onChanged();
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * Service account of a connection endpoint.
+     * </pre>
+     *
+     * <code>string service_account = 1;</code>
+     */
+    public Builder setServiceAccountBytes(
+        com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  checkByteStringIsUtf8(value);
+      identityOneofCase_ = 1;
+      identityOneof_ = value;
+      onChanged();
+      return this;
+    }
+
+    /**
+     * <pre>
+     * Hostname of a connection endpoint.
+     * </pre>
+     *
+     * <code>string hostname = 2;</code>
+     */
+    public java.lang.String getHostname() {
+      java.lang.Object ref = "";
+      if (identityOneofCase_ == 2) {
+        ref = identityOneof_;
+      }
+      if (!(ref instanceof java.lang.String)) {
+        com.google.protobuf.ByteString bs =
+            (com.google.protobuf.ByteString) ref;
+        java.lang.String s = bs.toStringUtf8();
+        if (identityOneofCase_ == 2) {
+          identityOneof_ = s;
+        }
+        return s;
+      } else {
+        return (java.lang.String) ref;
+      }
+    }
+    /**
+     * <pre>
+     * Hostname of a connection endpoint.
+     * </pre>
+     *
+     * <code>string hostname = 2;</code>
+     */
+    public com.google.protobuf.ByteString
+        getHostnameBytes() {
+      java.lang.Object ref = "";
+      if (identityOneofCase_ == 2) {
+        ref = identityOneof_;
+      }
+      if (ref instanceof String) {
+        com.google.protobuf.ByteString b = 
+            com.google.protobuf.ByteString.copyFromUtf8(
+                (java.lang.String) ref);
+        if (identityOneofCase_ == 2) {
+          identityOneof_ = b;
+        }
+        return b;
+      } else {
+        return (com.google.protobuf.ByteString) ref;
+      }
+    }
+    /**
+     * <pre>
+     * Hostname of a connection endpoint.
+     * </pre>
+     *
+     * <code>string hostname = 2;</code>
+     */
+    public Builder setHostname(
+        java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  identityOneofCase_ = 2;
+      identityOneof_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * Hostname of a connection endpoint.
+     * </pre>
+     *
+     * <code>string hostname = 2;</code>
+     */
+    public Builder clearHostname() {
+      if (identityOneofCase_ == 2) {
+        identityOneofCase_ = 0;
+        identityOneof_ = null;
+        onChanged();
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * Hostname of a connection endpoint.
+     * </pre>
+     *
+     * <code>string hostname = 2;</code>
+     */
+    public Builder setHostnameBytes(
+        com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  checkByteStringIsUtf8(value);
+      identityOneofCase_ = 2;
+      identityOneof_ = value;
+      onChanged();
+      return this;
+    }
+
+    private com.google.protobuf.MapField<
+        java.lang.String, java.lang.String> attributes_;
+    private com.google.protobuf.MapField<java.lang.String, java.lang.String>
+    internalGetAttributes() {
+      if (attributes_ == null) {
+        return com.google.protobuf.MapField.emptyMapField(
+            AttributesDefaultEntryHolder.defaultEntry);
+      }
+      return attributes_;
+    }
+    private com.google.protobuf.MapField<java.lang.String, java.lang.String>
+    internalGetMutableAttributes() {
+      onChanged();;
+      if (attributes_ == null) {
+        attributes_ = com.google.protobuf.MapField.newMapField(
+            AttributesDefaultEntryHolder.defaultEntry);
+      }
+      if (!attributes_.isMutable()) {
+        attributes_ = attributes_.copy();
+      }
+      return attributes_;
+    }
+
+    public int getAttributesCount() {
+      return internalGetAttributes().getMap().size();
+    }
+    /**
+     * <pre>
+     * Additional attributes of the identity.
+     * </pre>
+     *
+     * <code>map&lt;string, string&gt; attributes = 3;</code>
+     */
+
+    public boolean containsAttributes(
+        java.lang.String key) {
+      if (key == null) { throw new java.lang.NullPointerException(); }
+      return internalGetAttributes().getMap().containsKey(key);
+    }
+    /**
+     * Use {@link #getAttributesMap()} instead.
+     */
+    @java.lang.Deprecated
+    public java.util.Map<java.lang.String, java.lang.String> getAttributes() {
+      return getAttributesMap();
+    }
+    /**
+     * <pre>
+     * Additional attributes of the identity.
+     * </pre>
+     *
+     * <code>map&lt;string, string&gt; attributes = 3;</code>
+     */
+
+    public java.util.Map<java.lang.String, java.lang.String> getAttributesMap() {
+      return internalGetAttributes().getMap();
+    }
+    /**
+     * <pre>
+     * Additional attributes of the identity.
+     * </pre>
+     *
+     * <code>map&lt;string, string&gt; attributes = 3;</code>
+     */
+
+    public java.lang.String getAttributesOrDefault(
+        java.lang.String key,
+        java.lang.String defaultValue) {
+      if (key == null) { throw new java.lang.NullPointerException(); }
+      java.util.Map<java.lang.String, java.lang.String> map =
+          internalGetAttributes().getMap();
+      return map.containsKey(key) ? map.get(key) : defaultValue;
+    }
+    /**
+     * <pre>
+     * Additional attributes of the identity.
+     * </pre>
+     *
+     * <code>map&lt;string, string&gt; attributes = 3;</code>
+     */
+
+    public java.lang.String getAttributesOrThrow(
+        java.lang.String key) {
+      if (key == null) { throw new java.lang.NullPointerException(); }
+      java.util.Map<java.lang.String, java.lang.String> map =
+          internalGetAttributes().getMap();
+      if (!map.containsKey(key)) {
+        throw new java.lang.IllegalArgumentException();
+      }
+      return map.get(key);
+    }
+
+    public Builder clearAttributes() {
+      internalGetMutableAttributes().getMutableMap()
+          .clear();
+      return this;
+    }
+    /**
+     * <pre>
+     * Additional attributes of the identity.
+     * </pre>
+     *
+     * <code>map&lt;string, string&gt; attributes = 3;</code>
+     */
+
+    public Builder removeAttributes(
+        java.lang.String key) {
+      if (key == null) { throw new java.lang.NullPointerException(); }
+      internalGetMutableAttributes().getMutableMap()
+          .remove(key);
+      return this;
+    }
+    /**
+     * Use alternate mutation accessors instead.
+     */
+    @java.lang.Deprecated
+    public java.util.Map<java.lang.String, java.lang.String>
+    getMutableAttributes() {
+      return internalGetMutableAttributes().getMutableMap();
+    }
+    /**
+     * <pre>
+     * Additional attributes of the identity.
+     * </pre>
+     *
+     * <code>map&lt;string, string&gt; attributes = 3;</code>
+     */
+    public Builder putAttributes(
+        java.lang.String key,
+        java.lang.String value) {
+      if (key == null) { throw new java.lang.NullPointerException(); }
+      if (value == null) { throw new java.lang.NullPointerException(); }
+      internalGetMutableAttributes().getMutableMap()
+          .put(key, value);
+      return this;
+    }
+    /**
+     * <pre>
+     * Additional attributes of the identity.
+     * </pre>
+     *
+     * <code>map&lt;string, string&gt; attributes = 3;</code>
+     */
+
+    public Builder putAllAttributes(
+        java.util.Map<java.lang.String, java.lang.String> values) {
+      internalGetMutableAttributes().getMutableMap()
+          .putAll(values);
+      return this;
+    }
+    public final Builder setUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.setUnknownFieldsProto3(unknownFields);
+    }
+
+    public final Builder mergeUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.mergeUnknownFields(unknownFields);
+    }
+
+
+    // @@protoc_insertion_point(builder_scope:grpc.gcp.Identity)
+  }
+
+  // @@protoc_insertion_point(class_scope:grpc.gcp.Identity)
+  private static final io.grpc.alts.internal.Identity DEFAULT_INSTANCE;
+  static {
+    DEFAULT_INSTANCE = new io.grpc.alts.internal.Identity();
+  }
+
+  public static io.grpc.alts.internal.Identity getDefaultInstance() {
+    return DEFAULT_INSTANCE;
+  }
+
+  private static final com.google.protobuf.Parser<Identity>
+      PARSER = new com.google.protobuf.AbstractParser<Identity>() {
+    public Identity parsePartialFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return new Identity(input, extensionRegistry);
+    }
+  };
+
+  public static com.google.protobuf.Parser<Identity> parser() {
+    return PARSER;
+  }
+
+  @java.lang.Override
+  public com.google.protobuf.Parser<Identity> getParserForType() {
+    return PARSER;
+  }
+
+  public io.grpc.alts.internal.Identity getDefaultInstanceForType() {
+    return DEFAULT_INSTANCE;
+  }
+
+}
+
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/IdentityOrBuilder.java b/alts/src/generated/main/java/io/grpc/alts/internal/IdentityOrBuilder.java
new file mode 100644
index 0000000000..0cf096c4aa
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/IdentityOrBuilder.java
@@ -0,0 +1,101 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+public interface IdentityOrBuilder extends
+    // @@protoc_insertion_point(interface_extends:grpc.gcp.Identity)
+    com.google.protobuf.MessageOrBuilder {
+
+  /**
+   * <pre>
+   * Service account of a connection endpoint.
+   * </pre>
+   *
+   * <code>string service_account = 1;</code>
+   */
+  java.lang.String getServiceAccount();
+  /**
+   * <pre>
+   * Service account of a connection endpoint.
+   * </pre>
+   *
+   * <code>string service_account = 1;</code>
+   */
+  com.google.protobuf.ByteString
+      getServiceAccountBytes();
+
+  /**
+   * <pre>
+   * Hostname of a connection endpoint.
+   * </pre>
+   *
+   * <code>string hostname = 2;</code>
+   */
+  java.lang.String getHostname();
+  /**
+   * <pre>
+   * Hostname of a connection endpoint.
+   * </pre>
+   *
+   * <code>string hostname = 2;</code>
+   */
+  com.google.protobuf.ByteString
+      getHostnameBytes();
+
+  /**
+   * <pre>
+   * Additional attributes of the identity.
+   * </pre>
+   *
+   * <code>map&lt;string, string&gt; attributes = 3;</code>
+   */
+  int getAttributesCount();
+  /**
+   * <pre>
+   * Additional attributes of the identity.
+   * </pre>
+   *
+   * <code>map&lt;string, string&gt; attributes = 3;</code>
+   */
+  boolean containsAttributes(
+      java.lang.String key);
+  /**
+   * Use {@link #getAttributesMap()} instead.
+   */
+  @java.lang.Deprecated
+  java.util.Map<java.lang.String, java.lang.String>
+  getAttributes();
+  /**
+   * <pre>
+   * Additional attributes of the identity.
+   * </pre>
+   *
+   * <code>map&lt;string, string&gt; attributes = 3;</code>
+   */
+  java.util.Map<java.lang.String, java.lang.String>
+  getAttributesMap();
+  /**
+   * <pre>
+   * Additional attributes of the identity.
+   * </pre>
+   *
+   * <code>map&lt;string, string&gt; attributes = 3;</code>
+   */
+
+  java.lang.String getAttributesOrDefault(
+      java.lang.String key,
+      java.lang.String defaultValue);
+  /**
+   * <pre>
+   * Additional attributes of the identity.
+   * </pre>
+   *
+   * <code>map&lt;string, string&gt; attributes = 3;</code>
+   */
+
+  java.lang.String getAttributesOrThrow(
+      java.lang.String key);
+
+  public io.grpc.alts.internal.Identity.IdentityOneofCase getIdentityOneofCase();
+}
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/NetworkProtocol.java b/alts/src/generated/main/java/io/grpc/alts/internal/NetworkProtocol.java
new file mode 100644
index 0000000000..78b78a79dc
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/NetworkProtocol.java
@@ -0,0 +1,112 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+/**
+ * Protobuf enum {@code grpc.gcp.NetworkProtocol}
+ */
+public enum NetworkProtocol
+    implements com.google.protobuf.ProtocolMessageEnum {
+  /**
+   * <code>NETWORK_PROTOCOL_UNSPECIFIED = 0;</code>
+   */
+  NETWORK_PROTOCOL_UNSPECIFIED(0),
+  /**
+   * <code>TCP = 1;</code>
+   */
+  TCP(1),
+  /**
+   * <code>UDP = 2;</code>
+   */
+  UDP(2),
+  UNRECOGNIZED(-1),
+  ;
+
+  /**
+   * <code>NETWORK_PROTOCOL_UNSPECIFIED = 0;</code>
+   */
+  public static final int NETWORK_PROTOCOL_UNSPECIFIED_VALUE = 0;
+  /**
+   * <code>TCP = 1;</code>
+   */
+  public static final int TCP_VALUE = 1;
+  /**
+   * <code>UDP = 2;</code>
+   */
+  public static final int UDP_VALUE = 2;
+
+
+  public final int getNumber() {
+    if (this == UNRECOGNIZED) {
+      throw new java.lang.IllegalArgumentException(
+          "Can't get the number of an unknown enum value.");
+    }
+    return value;
+  }
+
+  /**
+   * @deprecated Use {@link #forNumber(int)} instead.
+   */
+  @java.lang.Deprecated
+  public static NetworkProtocol valueOf(int value) {
+    return forNumber(value);
+  }
+
+  public static NetworkProtocol forNumber(int value) {
+    switch (value) {
+      case 0: return NETWORK_PROTOCOL_UNSPECIFIED;
+      case 1: return TCP;
+      case 2: return UDP;
+      default: return null;
+    }
+  }
+
+  public static com.google.protobuf.Internal.EnumLiteMap<NetworkProtocol>
+      internalGetValueMap() {
+    return internalValueMap;
+  }
+  private static final com.google.protobuf.Internal.EnumLiteMap<
+      NetworkProtocol> internalValueMap =
+        new com.google.protobuf.Internal.EnumLiteMap<NetworkProtocol>() {
+          public NetworkProtocol findValueByNumber(int number) {
+            return NetworkProtocol.forNumber(number);
+          }
+        };
+
+  public final com.google.protobuf.Descriptors.EnumValueDescriptor
+      getValueDescriptor() {
+    return getDescriptor().getValues().get(ordinal());
+  }
+  public final com.google.protobuf.Descriptors.EnumDescriptor
+      getDescriptorForType() {
+    return getDescriptor();
+  }
+  public static final com.google.protobuf.Descriptors.EnumDescriptor
+      getDescriptor() {
+    return io.grpc.alts.internal.HandshakerProto.getDescriptor().getEnumTypes().get(1);
+  }
+
+  private static final NetworkProtocol[] VALUES = values();
+
+  public static NetworkProtocol valueOf(
+      com.google.protobuf.Descriptors.EnumValueDescriptor desc) {
+    if (desc.getType() != getDescriptor()) {
+      throw new java.lang.IllegalArgumentException(
+        "EnumValueDescriptor is not for this type.");
+    }
+    if (desc.getIndex() == -1) {
+      return UNRECOGNIZED;
+    }
+    return VALUES[desc.getIndex()];
+  }
+
+  private final int value;
+
+  private NetworkProtocol(int value) {
+    this.value = value;
+  }
+
+  // @@protoc_insertion_point(enum_scope:grpc.gcp.NetworkProtocol)
+}
+
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/NextHandshakeMessageReq.java b/alts/src/generated/main/java/io/grpc/alts/internal/NextHandshakeMessageReq.java
new file mode 100644
index 0000000000..7028aa9cca
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/NextHandshakeMessageReq.java
@@ -0,0 +1,474 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+/**
+ * Protobuf type {@code grpc.gcp.NextHandshakeMessageReq}
+ */
+public  final class NextHandshakeMessageReq extends
+    com.google.protobuf.GeneratedMessageV3 implements
+    // @@protoc_insertion_point(message_implements:grpc.gcp.NextHandshakeMessageReq)
+    NextHandshakeMessageReqOrBuilder {
+private static final long serialVersionUID = 0L;
+  // Use NextHandshakeMessageReq.newBuilder() to construct.
+  private NextHandshakeMessageReq(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
+    super(builder);
+  }
+  private NextHandshakeMessageReq() {
+    inBytes_ = com.google.protobuf.ByteString.EMPTY;
+  }
+
+  @java.lang.Override
+  public final com.google.protobuf.UnknownFieldSet
+  getUnknownFields() {
+    return this.unknownFields;
+  }
+  private NextHandshakeMessageReq(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    this();
+    if (extensionRegistry == null) {
+      throw new java.lang.NullPointerException();
+    }
+    int mutable_bitField0_ = 0;
+    com.google.protobuf.UnknownFieldSet.Builder unknownFields =
+        com.google.protobuf.UnknownFieldSet.newBuilder();
+    try {
+      boolean done = false;
+      while (!done) {
+        int tag = input.readTag();
+        switch (tag) {
+          case 0:
+            done = true;
+            break;
+          default: {
+            if (!parseUnknownFieldProto3(
+                input, unknownFields, extensionRegistry, tag)) {
+              done = true;
+            }
+            break;
+          }
+          case 10: {
+
+            inBytes_ = input.readBytes();
+            break;
+          }
+        }
+      }
+    } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+      throw e.setUnfinishedMessage(this);
+    } catch (java.io.IOException e) {
+      throw new com.google.protobuf.InvalidProtocolBufferException(
+          e).setUnfinishedMessage(this);
+    } finally {
+      this.unknownFields = unknownFields.build();
+      makeExtensionsImmutable();
+    }
+  }
+  public static final com.google.protobuf.Descriptors.Descriptor
+      getDescriptor() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_NextHandshakeMessageReq_descriptor;
+  }
+
+  protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internalGetFieldAccessorTable() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_NextHandshakeMessageReq_fieldAccessorTable
+        .ensureFieldAccessorsInitialized(
+            io.grpc.alts.internal.NextHandshakeMessageReq.class, io.grpc.alts.internal.NextHandshakeMessageReq.Builder.class);
+  }
+
+  public static final int IN_BYTES_FIELD_NUMBER = 1;
+  private com.google.protobuf.ByteString inBytes_;
+  /**
+   * <pre>
+   * Bytes in out_frames returned from the peer's HandshakerResp. It is possible
+   * that the peer's out_frames are split into multiple NextHandshakerMessageReq
+   * messages.
+   * </pre>
+   *
+   * <code>bytes in_bytes = 1;</code>
+   */
+  public com.google.protobuf.ByteString getInBytes() {
+    return inBytes_;
+  }
+
+  private byte memoizedIsInitialized = -1;
+  public final boolean isInitialized() {
+    byte isInitialized = memoizedIsInitialized;
+    if (isInitialized == 1) return true;
+    if (isInitialized == 0) return false;
+
+    memoizedIsInitialized = 1;
+    return true;
+  }
+
+  public void writeTo(com.google.protobuf.CodedOutputStream output)
+                      throws java.io.IOException {
+    if (!inBytes_.isEmpty()) {
+      output.writeBytes(1, inBytes_);
+    }
+    unknownFields.writeTo(output);
+  }
+
+  public int getSerializedSize() {
+    int size = memoizedSize;
+    if (size != -1) return size;
+
+    size = 0;
+    if (!inBytes_.isEmpty()) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeBytesSize(1, inBytes_);
+    }
+    size += unknownFields.getSerializedSize();
+    memoizedSize = size;
+    return size;
+  }
+
+  @java.lang.Override
+  public boolean equals(final java.lang.Object obj) {
+    if (obj == this) {
+     return true;
+    }
+    if (!(obj instanceof io.grpc.alts.internal.NextHandshakeMessageReq)) {
+      return super.equals(obj);
+    }
+    io.grpc.alts.internal.NextHandshakeMessageReq other = (io.grpc.alts.internal.NextHandshakeMessageReq) obj;
+
+    boolean result = true;
+    result = result && getInBytes()
+        .equals(other.getInBytes());
+    result = result && unknownFields.equals(other.unknownFields);
+    return result;
+  }
+
+  @java.lang.Override
+  public int hashCode() {
+    if (memoizedHashCode != 0) {
+      return memoizedHashCode;
+    }
+    int hash = 41;
+    hash = (19 * hash) + getDescriptor().hashCode();
+    hash = (37 * hash) + IN_BYTES_FIELD_NUMBER;
+    hash = (53 * hash) + getInBytes().hashCode();
+    hash = (29 * hash) + unknownFields.hashCode();
+    memoizedHashCode = hash;
+    return hash;
+  }
+
+  public static io.grpc.alts.internal.NextHandshakeMessageReq parseFrom(
+      java.nio.ByteBuffer data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.NextHandshakeMessageReq parseFrom(
+      java.nio.ByteBuffer data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.NextHandshakeMessageReq parseFrom(
+      com.google.protobuf.ByteString data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.NextHandshakeMessageReq parseFrom(
+      com.google.protobuf.ByteString data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.NextHandshakeMessageReq parseFrom(byte[] data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.NextHandshakeMessageReq parseFrom(
+      byte[] data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.NextHandshakeMessageReq parseFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.NextHandshakeMessageReq parseFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.NextHandshakeMessageReq parseDelimitedFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.NextHandshakeMessageReq parseDelimitedFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.NextHandshakeMessageReq parseFrom(
+      com.google.protobuf.CodedInputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.NextHandshakeMessageReq parseFrom(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+
+  public Builder newBuilderForType() { return newBuilder(); }
+  public static Builder newBuilder() {
+    return DEFAULT_INSTANCE.toBuilder();
+  }
+  public static Builder newBuilder(io.grpc.alts.internal.NextHandshakeMessageReq prototype) {
+    return DEFAULT_INSTANCE.toBuilder().mergeFrom(prototype);
+  }
+  public Builder toBuilder() {
+    return this == DEFAULT_INSTANCE
+        ? new Builder() : new Builder().mergeFrom(this);
+  }
+
+  @java.lang.Override
+  protected Builder newBuilderForType(
+      com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+    Builder builder = new Builder(parent);
+    return builder;
+  }
+  /**
+   * Protobuf type {@code grpc.gcp.NextHandshakeMessageReq}
+   */
+  public static final class Builder extends
+      com.google.protobuf.GeneratedMessageV3.Builder<Builder> implements
+      // @@protoc_insertion_point(builder_implements:grpc.gcp.NextHandshakeMessageReq)
+      io.grpc.alts.internal.NextHandshakeMessageReqOrBuilder {
+    public static final com.google.protobuf.Descriptors.Descriptor
+        getDescriptor() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_NextHandshakeMessageReq_descriptor;
+    }
+
+    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+        internalGetFieldAccessorTable() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_NextHandshakeMessageReq_fieldAccessorTable
+          .ensureFieldAccessorsInitialized(
+              io.grpc.alts.internal.NextHandshakeMessageReq.class, io.grpc.alts.internal.NextHandshakeMessageReq.Builder.class);
+    }
+
+    // Construct using io.grpc.alts.internal.NextHandshakeMessageReq.newBuilder()
+    private Builder() {
+      maybeForceBuilderInitialization();
+    }
+
+    private Builder(
+        com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+      super(parent);
+      maybeForceBuilderInitialization();
+    }
+    private void maybeForceBuilderInitialization() {
+      if (com.google.protobuf.GeneratedMessageV3
+              .alwaysUseFieldBuilders) {
+      }
+    }
+    public Builder clear() {
+      super.clear();
+      inBytes_ = com.google.protobuf.ByteString.EMPTY;
+
+      return this;
+    }
+
+    public com.google.protobuf.Descriptors.Descriptor
+        getDescriptorForType() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_NextHandshakeMessageReq_descriptor;
+    }
+
+    public io.grpc.alts.internal.NextHandshakeMessageReq getDefaultInstanceForType() {
+      return io.grpc.alts.internal.NextHandshakeMessageReq.getDefaultInstance();
+    }
+
+    public io.grpc.alts.internal.NextHandshakeMessageReq build() {
+      io.grpc.alts.internal.NextHandshakeMessageReq result = buildPartial();
+      if (!result.isInitialized()) {
+        throw newUninitializedMessageException(result);
+      }
+      return result;
+    }
+
+    public io.grpc.alts.internal.NextHandshakeMessageReq buildPartial() {
+      io.grpc.alts.internal.NextHandshakeMessageReq result = new io.grpc.alts.internal.NextHandshakeMessageReq(this);
+      result.inBytes_ = inBytes_;
+      onBuilt();
+      return result;
+    }
+
+    public Builder clone() {
+      return (Builder) super.clone();
+    }
+    public Builder setField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.setField(field, value);
+    }
+    public Builder clearField(
+        com.google.protobuf.Descriptors.FieldDescriptor field) {
+      return (Builder) super.clearField(field);
+    }
+    public Builder clearOneof(
+        com.google.protobuf.Descriptors.OneofDescriptor oneof) {
+      return (Builder) super.clearOneof(oneof);
+    }
+    public Builder setRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        int index, java.lang.Object value) {
+      return (Builder) super.setRepeatedField(field, index, value);
+    }
+    public Builder addRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.addRepeatedField(field, value);
+    }
+    public Builder mergeFrom(com.google.protobuf.Message other) {
+      if (other instanceof io.grpc.alts.internal.NextHandshakeMessageReq) {
+        return mergeFrom((io.grpc.alts.internal.NextHandshakeMessageReq)other);
+      } else {
+        super.mergeFrom(other);
+        return this;
+      }
+    }
+
+    public Builder mergeFrom(io.grpc.alts.internal.NextHandshakeMessageReq other) {
+      if (other == io.grpc.alts.internal.NextHandshakeMessageReq.getDefaultInstance()) return this;
+      if (other.getInBytes() != com.google.protobuf.ByteString.EMPTY) {
+        setInBytes(other.getInBytes());
+      }
+      this.mergeUnknownFields(other.unknownFields);
+      onChanged();
+      return this;
+    }
+
+    public final boolean isInitialized() {
+      return true;
+    }
+
+    public Builder mergeFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      io.grpc.alts.internal.NextHandshakeMessageReq parsedMessage = null;
+      try {
+        parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);
+      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+        parsedMessage = (io.grpc.alts.internal.NextHandshakeMessageReq) e.getUnfinishedMessage();
+        throw e.unwrapIOException();
+      } finally {
+        if (parsedMessage != null) {
+          mergeFrom(parsedMessage);
+        }
+      }
+      return this;
+    }
+
+    private com.google.protobuf.ByteString inBytes_ = com.google.protobuf.ByteString.EMPTY;
+    /**
+     * <pre>
+     * Bytes in out_frames returned from the peer's HandshakerResp. It is possible
+     * that the peer's out_frames are split into multiple NextHandshakerMessageReq
+     * messages.
+     * </pre>
+     *
+     * <code>bytes in_bytes = 1;</code>
+     */
+    public com.google.protobuf.ByteString getInBytes() {
+      return inBytes_;
+    }
+    /**
+     * <pre>
+     * Bytes in out_frames returned from the peer's HandshakerResp. It is possible
+     * that the peer's out_frames are split into multiple NextHandshakerMessageReq
+     * messages.
+     * </pre>
+     *
+     * <code>bytes in_bytes = 1;</code>
+     */
+    public Builder setInBytes(com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  
+      inBytes_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * Bytes in out_frames returned from the peer's HandshakerResp. It is possible
+     * that the peer's out_frames are split into multiple NextHandshakerMessageReq
+     * messages.
+     * </pre>
+     *
+     * <code>bytes in_bytes = 1;</code>
+     */
+    public Builder clearInBytes() {
+      
+      inBytes_ = getDefaultInstance().getInBytes();
+      onChanged();
+      return this;
+    }
+    public final Builder setUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.setUnknownFieldsProto3(unknownFields);
+    }
+
+    public final Builder mergeUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.mergeUnknownFields(unknownFields);
+    }
+
+
+    // @@protoc_insertion_point(builder_scope:grpc.gcp.NextHandshakeMessageReq)
+  }
+
+  // @@protoc_insertion_point(class_scope:grpc.gcp.NextHandshakeMessageReq)
+  private static final io.grpc.alts.internal.NextHandshakeMessageReq DEFAULT_INSTANCE;
+  static {
+    DEFAULT_INSTANCE = new io.grpc.alts.internal.NextHandshakeMessageReq();
+  }
+
+  public static io.grpc.alts.internal.NextHandshakeMessageReq getDefaultInstance() {
+    return DEFAULT_INSTANCE;
+  }
+
+  private static final com.google.protobuf.Parser<NextHandshakeMessageReq>
+      PARSER = new com.google.protobuf.AbstractParser<NextHandshakeMessageReq>() {
+    public NextHandshakeMessageReq parsePartialFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return new NextHandshakeMessageReq(input, extensionRegistry);
+    }
+  };
+
+  public static com.google.protobuf.Parser<NextHandshakeMessageReq> parser() {
+    return PARSER;
+  }
+
+  @java.lang.Override
+  public com.google.protobuf.Parser<NextHandshakeMessageReq> getParserForType() {
+    return PARSER;
+  }
+
+  public io.grpc.alts.internal.NextHandshakeMessageReq getDefaultInstanceForType() {
+    return DEFAULT_INSTANCE;
+  }
+
+}
+
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/NextHandshakeMessageReqOrBuilder.java b/alts/src/generated/main/java/io/grpc/alts/internal/NextHandshakeMessageReqOrBuilder.java
new file mode 100644
index 0000000000..3c3f0a57fc
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/NextHandshakeMessageReqOrBuilder.java
@@ -0,0 +1,20 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+public interface NextHandshakeMessageReqOrBuilder extends
+    // @@protoc_insertion_point(interface_extends:grpc.gcp.NextHandshakeMessageReq)
+    com.google.protobuf.MessageOrBuilder {
+
+  /**
+   * <pre>
+   * Bytes in out_frames returned from the peer's HandshakerResp. It is possible
+   * that the peer's out_frames are split into multiple NextHandshakerMessageReq
+   * messages.
+   * </pre>
+   *
+   * <code>bytes in_bytes = 1;</code>
+   */
+  com.google.protobuf.ByteString getInBytes();
+}
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/RpcProtocolVersions.java b/alts/src/generated/main/java/io/grpc/alts/internal/RpcProtocolVersions.java
new file mode 100644
index 0000000000..e415be2616
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/RpcProtocolVersions.java
@@ -0,0 +1,1377 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/transport_security_common.proto
+
+package io.grpc.alts.internal;
+
+/**
+ * <pre>
+ * Max and min supported RPC protocol versions.
+ * </pre>
+ *
+ * Protobuf type {@code grpc.gcp.RpcProtocolVersions}
+ */
+public  final class RpcProtocolVersions extends
+    com.google.protobuf.GeneratedMessageV3 implements
+    // @@protoc_insertion_point(message_implements:grpc.gcp.RpcProtocolVersions)
+    RpcProtocolVersionsOrBuilder {
+private static final long serialVersionUID = 0L;
+  // Use RpcProtocolVersions.newBuilder() to construct.
+  private RpcProtocolVersions(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
+    super(builder);
+  }
+  private RpcProtocolVersions() {
+  }
+
+  @java.lang.Override
+  public final com.google.protobuf.UnknownFieldSet
+  getUnknownFields() {
+    return this.unknownFields;
+  }
+  private RpcProtocolVersions(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    this();
+    if (extensionRegistry == null) {
+      throw new java.lang.NullPointerException();
+    }
+    int mutable_bitField0_ = 0;
+    com.google.protobuf.UnknownFieldSet.Builder unknownFields =
+        com.google.protobuf.UnknownFieldSet.newBuilder();
+    try {
+      boolean done = false;
+      while (!done) {
+        int tag = input.readTag();
+        switch (tag) {
+          case 0:
+            done = true;
+            break;
+          default: {
+            if (!parseUnknownFieldProto3(
+                input, unknownFields, extensionRegistry, tag)) {
+              done = true;
+            }
+            break;
+          }
+          case 10: {
+            io.grpc.alts.internal.RpcProtocolVersions.Version.Builder subBuilder = null;
+            if (maxRpcVersion_ != null) {
+              subBuilder = maxRpcVersion_.toBuilder();
+            }
+            maxRpcVersion_ = input.readMessage(io.grpc.alts.internal.RpcProtocolVersions.Version.parser(), extensionRegistry);
+            if (subBuilder != null) {
+              subBuilder.mergeFrom(maxRpcVersion_);
+              maxRpcVersion_ = subBuilder.buildPartial();
+            }
+
+            break;
+          }
+          case 18: {
+            io.grpc.alts.internal.RpcProtocolVersions.Version.Builder subBuilder = null;
+            if (minRpcVersion_ != null) {
+              subBuilder = minRpcVersion_.toBuilder();
+            }
+            minRpcVersion_ = input.readMessage(io.grpc.alts.internal.RpcProtocolVersions.Version.parser(), extensionRegistry);
+            if (subBuilder != null) {
+              subBuilder.mergeFrom(minRpcVersion_);
+              minRpcVersion_ = subBuilder.buildPartial();
+            }
+
+            break;
+          }
+        }
+      }
+    } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+      throw e.setUnfinishedMessage(this);
+    } catch (java.io.IOException e) {
+      throw new com.google.protobuf.InvalidProtocolBufferException(
+          e).setUnfinishedMessage(this);
+    } finally {
+      this.unknownFields = unknownFields.build();
+      makeExtensionsImmutable();
+    }
+  }
+  public static final com.google.protobuf.Descriptors.Descriptor
+      getDescriptor() {
+    return io.grpc.alts.internal.TransportSecurityCommonProto.internal_static_grpc_gcp_RpcProtocolVersions_descriptor;
+  }
+
+  protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internalGetFieldAccessorTable() {
+    return io.grpc.alts.internal.TransportSecurityCommonProto.internal_static_grpc_gcp_RpcProtocolVersions_fieldAccessorTable
+        .ensureFieldAccessorsInitialized(
+            io.grpc.alts.internal.RpcProtocolVersions.class, io.grpc.alts.internal.RpcProtocolVersions.Builder.class);
+  }
+
+  public interface VersionOrBuilder extends
+      // @@protoc_insertion_point(interface_extends:grpc.gcp.RpcProtocolVersions.Version)
+      com.google.protobuf.MessageOrBuilder {
+
+    /**
+     * <code>uint32 major = 1;</code>
+     */
+    int getMajor();
+
+    /**
+     * <code>uint32 minor = 2;</code>
+     */
+    int getMinor();
+  }
+  /**
+   * <pre>
+   * RPC version contains a major version and a minor version.
+   * </pre>
+   *
+   * Protobuf type {@code grpc.gcp.RpcProtocolVersions.Version}
+   */
+  public  static final class Version extends
+      com.google.protobuf.GeneratedMessageV3 implements
+      // @@protoc_insertion_point(message_implements:grpc.gcp.RpcProtocolVersions.Version)
+      VersionOrBuilder {
+  private static final long serialVersionUID = 0L;
+    // Use Version.newBuilder() to construct.
+    private Version(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
+      super(builder);
+    }
+    private Version() {
+      major_ = 0;
+      minor_ = 0;
+    }
+
+    @java.lang.Override
+    public final com.google.protobuf.UnknownFieldSet
+    getUnknownFields() {
+      return this.unknownFields;
+    }
+    private Version(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      this();
+      if (extensionRegistry == null) {
+        throw new java.lang.NullPointerException();
+      }
+      int mutable_bitField0_ = 0;
+      com.google.protobuf.UnknownFieldSet.Builder unknownFields =
+          com.google.protobuf.UnknownFieldSet.newBuilder();
+      try {
+        boolean done = false;
+        while (!done) {
+          int tag = input.readTag();
+          switch (tag) {
+            case 0:
+              done = true;
+              break;
+            default: {
+              if (!parseUnknownFieldProto3(
+                  input, unknownFields, extensionRegistry, tag)) {
+                done = true;
+              }
+              break;
+            }
+            case 8: {
+
+              major_ = input.readUInt32();
+              break;
+            }
+            case 16: {
+
+              minor_ = input.readUInt32();
+              break;
+            }
+          }
+        }
+      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+        throw e.setUnfinishedMessage(this);
+      } catch (java.io.IOException e) {
+        throw new com.google.protobuf.InvalidProtocolBufferException(
+            e).setUnfinishedMessage(this);
+      } finally {
+        this.unknownFields = unknownFields.build();
+        makeExtensionsImmutable();
+      }
+    }
+    public static final com.google.protobuf.Descriptors.Descriptor
+        getDescriptor() {
+      return io.grpc.alts.internal.TransportSecurityCommonProto.internal_static_grpc_gcp_RpcProtocolVersions_Version_descriptor;
+    }
+
+    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+        internalGetFieldAccessorTable() {
+      return io.grpc.alts.internal.TransportSecurityCommonProto.internal_static_grpc_gcp_RpcProtocolVersions_Version_fieldAccessorTable
+          .ensureFieldAccessorsInitialized(
+              io.grpc.alts.internal.RpcProtocolVersions.Version.class, io.grpc.alts.internal.RpcProtocolVersions.Version.Builder.class);
+    }
+
+    public static final int MAJOR_FIELD_NUMBER = 1;
+    private int major_;
+    /**
+     * <code>uint32 major = 1;</code>
+     */
+    public int getMajor() {
+      return major_;
+    }
+
+    public static final int MINOR_FIELD_NUMBER = 2;
+    private int minor_;
+    /**
+     * <code>uint32 minor = 2;</code>
+     */
+    public int getMinor() {
+      return minor_;
+    }
+
+    private byte memoizedIsInitialized = -1;
+    public final boolean isInitialized() {
+      byte isInitialized = memoizedIsInitialized;
+      if (isInitialized == 1) return true;
+      if (isInitialized == 0) return false;
+
+      memoizedIsInitialized = 1;
+      return true;
+    }
+
+    public void writeTo(com.google.protobuf.CodedOutputStream output)
+                        throws java.io.IOException {
+      if (major_ != 0) {
+        output.writeUInt32(1, major_);
+      }
+      if (minor_ != 0) {
+        output.writeUInt32(2, minor_);
+      }
+      unknownFields.writeTo(output);
+    }
+
+    public int getSerializedSize() {
+      int size = memoizedSize;
+      if (size != -1) return size;
+
+      size = 0;
+      if (major_ != 0) {
+        size += com.google.protobuf.CodedOutputStream
+          .computeUInt32Size(1, major_);
+      }
+      if (minor_ != 0) {
+        size += com.google.protobuf.CodedOutputStream
+          .computeUInt32Size(2, minor_);
+      }
+      size += unknownFields.getSerializedSize();
+      memoizedSize = size;
+      return size;
+    }
+
+    @java.lang.Override
+    public boolean equals(final java.lang.Object obj) {
+      if (obj == this) {
+       return true;
+      }
+      if (!(obj instanceof io.grpc.alts.internal.RpcProtocolVersions.Version)) {
+        return super.equals(obj);
+      }
+      io.grpc.alts.internal.RpcProtocolVersions.Version other = (io.grpc.alts.internal.RpcProtocolVersions.Version) obj;
+
+      boolean result = true;
+      result = result && (getMajor()
+          == other.getMajor());
+      result = result && (getMinor()
+          == other.getMinor());
+      result = result && unknownFields.equals(other.unknownFields);
+      return result;
+    }
+
+    @java.lang.Override
+    public int hashCode() {
+      if (memoizedHashCode != 0) {
+        return memoizedHashCode;
+      }
+      int hash = 41;
+      hash = (19 * hash) + getDescriptor().hashCode();
+      hash = (37 * hash) + MAJOR_FIELD_NUMBER;
+      hash = (53 * hash) + getMajor();
+      hash = (37 * hash) + MINOR_FIELD_NUMBER;
+      hash = (53 * hash) + getMinor();
+      hash = (29 * hash) + unknownFields.hashCode();
+      memoizedHashCode = hash;
+      return hash;
+    }
+
+    public static io.grpc.alts.internal.RpcProtocolVersions.Version parseFrom(
+        java.nio.ByteBuffer data)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return PARSER.parseFrom(data);
+    }
+    public static io.grpc.alts.internal.RpcProtocolVersions.Version parseFrom(
+        java.nio.ByteBuffer data,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return PARSER.parseFrom(data, extensionRegistry);
+    }
+    public static io.grpc.alts.internal.RpcProtocolVersions.Version parseFrom(
+        com.google.protobuf.ByteString data)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return PARSER.parseFrom(data);
+    }
+    public static io.grpc.alts.internal.RpcProtocolVersions.Version parseFrom(
+        com.google.protobuf.ByteString data,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return PARSER.parseFrom(data, extensionRegistry);
+    }
+    public static io.grpc.alts.internal.RpcProtocolVersions.Version parseFrom(byte[] data)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return PARSER.parseFrom(data);
+    }
+    public static io.grpc.alts.internal.RpcProtocolVersions.Version parseFrom(
+        byte[] data,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return PARSER.parseFrom(data, extensionRegistry);
+    }
+    public static io.grpc.alts.internal.RpcProtocolVersions.Version parseFrom(java.io.InputStream input)
+        throws java.io.IOException {
+      return com.google.protobuf.GeneratedMessageV3
+          .parseWithIOException(PARSER, input);
+    }
+    public static io.grpc.alts.internal.RpcProtocolVersions.Version parseFrom(
+        java.io.InputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      return com.google.protobuf.GeneratedMessageV3
+          .parseWithIOException(PARSER, input, extensionRegistry);
+    }
+    public static io.grpc.alts.internal.RpcProtocolVersions.Version parseDelimitedFrom(java.io.InputStream input)
+        throws java.io.IOException {
+      return com.google.protobuf.GeneratedMessageV3
+          .parseDelimitedWithIOException(PARSER, input);
+    }
+    public static io.grpc.alts.internal.RpcProtocolVersions.Version parseDelimitedFrom(
+        java.io.InputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      return com.google.protobuf.GeneratedMessageV3
+          .parseDelimitedWithIOException(PARSER, input, extensionRegistry);
+    }
+    public static io.grpc.alts.internal.RpcProtocolVersions.Version parseFrom(
+        com.google.protobuf.CodedInputStream input)
+        throws java.io.IOException {
+      return com.google.protobuf.GeneratedMessageV3
+          .parseWithIOException(PARSER, input);
+    }
+    public static io.grpc.alts.internal.RpcProtocolVersions.Version parseFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      return com.google.protobuf.GeneratedMessageV3
+          .parseWithIOException(PARSER, input, extensionRegistry);
+    }
+
+    public Builder newBuilderForType() { return newBuilder(); }
+    public static Builder newBuilder() {
+      return DEFAULT_INSTANCE.toBuilder();
+    }
+    public static Builder newBuilder(io.grpc.alts.internal.RpcProtocolVersions.Version prototype) {
+      return DEFAULT_INSTANCE.toBuilder().mergeFrom(prototype);
+    }
+    public Builder toBuilder() {
+      return this == DEFAULT_INSTANCE
+          ? new Builder() : new Builder().mergeFrom(this);
+    }
+
+    @java.lang.Override
+    protected Builder newBuilderForType(
+        com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+      Builder builder = new Builder(parent);
+      return builder;
+    }
+    /**
+     * <pre>
+     * RPC version contains a major version and a minor version.
+     * </pre>
+     *
+     * Protobuf type {@code grpc.gcp.RpcProtocolVersions.Version}
+     */
+    public static final class Builder extends
+        com.google.protobuf.GeneratedMessageV3.Builder<Builder> implements
+        // @@protoc_insertion_point(builder_implements:grpc.gcp.RpcProtocolVersions.Version)
+        io.grpc.alts.internal.RpcProtocolVersions.VersionOrBuilder {
+      public static final com.google.protobuf.Descriptors.Descriptor
+          getDescriptor() {
+        return io.grpc.alts.internal.TransportSecurityCommonProto.internal_static_grpc_gcp_RpcProtocolVersions_Version_descriptor;
+      }
+
+      protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+          internalGetFieldAccessorTable() {
+        return io.grpc.alts.internal.TransportSecurityCommonProto.internal_static_grpc_gcp_RpcProtocolVersions_Version_fieldAccessorTable
+            .ensureFieldAccessorsInitialized(
+                io.grpc.alts.internal.RpcProtocolVersions.Version.class, io.grpc.alts.internal.RpcProtocolVersions.Version.Builder.class);
+      }
+
+      // Construct using io.grpc.alts.internal.RpcProtocolVersions.Version.newBuilder()
+      private Builder() {
+        maybeForceBuilderInitialization();
+      }
+
+      private Builder(
+          com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+        super(parent);
+        maybeForceBuilderInitialization();
+      }
+      private void maybeForceBuilderInitialization() {
+        if (com.google.protobuf.GeneratedMessageV3
+                .alwaysUseFieldBuilders) {
+        }
+      }
+      public Builder clear() {
+        super.clear();
+        major_ = 0;
+
+        minor_ = 0;
+
+        return this;
+      }
+
+      public com.google.protobuf.Descriptors.Descriptor
+          getDescriptorForType() {
+        return io.grpc.alts.internal.TransportSecurityCommonProto.internal_static_grpc_gcp_RpcProtocolVersions_Version_descriptor;
+      }
+
+      public io.grpc.alts.internal.RpcProtocolVersions.Version getDefaultInstanceForType() {
+        return io.grpc.alts.internal.RpcProtocolVersions.Version.getDefaultInstance();
+      }
+
+      public io.grpc.alts.internal.RpcProtocolVersions.Version build() {
+        io.grpc.alts.internal.RpcProtocolVersions.Version result = buildPartial();
+        if (!result.isInitialized()) {
+          throw newUninitializedMessageException(result);
+        }
+        return result;
+      }
+
+      public io.grpc.alts.internal.RpcProtocolVersions.Version buildPartial() {
+        io.grpc.alts.internal.RpcProtocolVersions.Version result = new io.grpc.alts.internal.RpcProtocolVersions.Version(this);
+        result.major_ = major_;
+        result.minor_ = minor_;
+        onBuilt();
+        return result;
+      }
+
+      public Builder clone() {
+        return (Builder) super.clone();
+      }
+      public Builder setField(
+          com.google.protobuf.Descriptors.FieldDescriptor field,
+          java.lang.Object value) {
+        return (Builder) super.setField(field, value);
+      }
+      public Builder clearField(
+          com.google.protobuf.Descriptors.FieldDescriptor field) {
+        return (Builder) super.clearField(field);
+      }
+      public Builder clearOneof(
+          com.google.protobuf.Descriptors.OneofDescriptor oneof) {
+        return (Builder) super.clearOneof(oneof);
+      }
+      public Builder setRepeatedField(
+          com.google.protobuf.Descriptors.FieldDescriptor field,
+          int index, java.lang.Object value) {
+        return (Builder) super.setRepeatedField(field, index, value);
+      }
+      public Builder addRepeatedField(
+          com.google.protobuf.Descriptors.FieldDescriptor field,
+          java.lang.Object value) {
+        return (Builder) super.addRepeatedField(field, value);
+      }
+      public Builder mergeFrom(com.google.protobuf.Message other) {
+        if (other instanceof io.grpc.alts.internal.RpcProtocolVersions.Version) {
+          return mergeFrom((io.grpc.alts.internal.RpcProtocolVersions.Version)other);
+        } else {
+          super.mergeFrom(other);
+          return this;
+        }
+      }
+
+      public Builder mergeFrom(io.grpc.alts.internal.RpcProtocolVersions.Version other) {
+        if (other == io.grpc.alts.internal.RpcProtocolVersions.Version.getDefaultInstance()) return this;
+        if (other.getMajor() != 0) {
+          setMajor(other.getMajor());
+        }
+        if (other.getMinor() != 0) {
+          setMinor(other.getMinor());
+        }
+        this.mergeUnknownFields(other.unknownFields);
+        onChanged();
+        return this;
+      }
+
+      public final boolean isInitialized() {
+        return true;
+      }
+
+      public Builder mergeFrom(
+          com.google.protobuf.CodedInputStream input,
+          com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+          throws java.io.IOException {
+        io.grpc.alts.internal.RpcProtocolVersions.Version parsedMessage = null;
+        try {
+          parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);
+        } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+          parsedMessage = (io.grpc.alts.internal.RpcProtocolVersions.Version) e.getUnfinishedMessage();
+          throw e.unwrapIOException();
+        } finally {
+          if (parsedMessage != null) {
+            mergeFrom(parsedMessage);
+          }
+        }
+        return this;
+      }
+
+      private int major_ ;
+      /**
+       * <code>uint32 major = 1;</code>
+       */
+      public int getMajor() {
+        return major_;
+      }
+      /**
+       * <code>uint32 major = 1;</code>
+       */
+      public Builder setMajor(int value) {
+        
+        major_ = value;
+        onChanged();
+        return this;
+      }
+      /**
+       * <code>uint32 major = 1;</code>
+       */
+      public Builder clearMajor() {
+        
+        major_ = 0;
+        onChanged();
+        return this;
+      }
+
+      private int minor_ ;
+      /**
+       * <code>uint32 minor = 2;</code>
+       */
+      public int getMinor() {
+        return minor_;
+      }
+      /**
+       * <code>uint32 minor = 2;</code>
+       */
+      public Builder setMinor(int value) {
+        
+        minor_ = value;
+        onChanged();
+        return this;
+      }
+      /**
+       * <code>uint32 minor = 2;</code>
+       */
+      public Builder clearMinor() {
+        
+        minor_ = 0;
+        onChanged();
+        return this;
+      }
+      public final Builder setUnknownFields(
+          final com.google.protobuf.UnknownFieldSet unknownFields) {
+        return super.setUnknownFieldsProto3(unknownFields);
+      }
+
+      public final Builder mergeUnknownFields(
+          final com.google.protobuf.UnknownFieldSet unknownFields) {
+        return super.mergeUnknownFields(unknownFields);
+      }
+
+
+      // @@protoc_insertion_point(builder_scope:grpc.gcp.RpcProtocolVersions.Version)
+    }
+
+    // @@protoc_insertion_point(class_scope:grpc.gcp.RpcProtocolVersions.Version)
+    private static final io.grpc.alts.internal.RpcProtocolVersions.Version DEFAULT_INSTANCE;
+    static {
+      DEFAULT_INSTANCE = new io.grpc.alts.internal.RpcProtocolVersions.Version();
+    }
+
+    public static io.grpc.alts.internal.RpcProtocolVersions.Version getDefaultInstance() {
+      return DEFAULT_INSTANCE;
+    }
+
+    private static final com.google.protobuf.Parser<Version>
+        PARSER = new com.google.protobuf.AbstractParser<Version>() {
+      public Version parsePartialFrom(
+          com.google.protobuf.CodedInputStream input,
+          com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+          throws com.google.protobuf.InvalidProtocolBufferException {
+        return new Version(input, extensionRegistry);
+      }
+    };
+
+    public static com.google.protobuf.Parser<Version> parser() {
+      return PARSER;
+    }
+
+    @java.lang.Override
+    public com.google.protobuf.Parser<Version> getParserForType() {
+      return PARSER;
+    }
+
+    public io.grpc.alts.internal.RpcProtocolVersions.Version getDefaultInstanceForType() {
+      return DEFAULT_INSTANCE;
+    }
+
+  }
+
+  public static final int MAX_RPC_VERSION_FIELD_NUMBER = 1;
+  private io.grpc.alts.internal.RpcProtocolVersions.Version maxRpcVersion_;
+  /**
+   * <pre>
+   * Maximum supported RPC version.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
+   */
+  public boolean hasMaxRpcVersion() {
+    return maxRpcVersion_ != null;
+  }
+  /**
+   * <pre>
+   * Maximum supported RPC version.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
+   */
+  public io.grpc.alts.internal.RpcProtocolVersions.Version getMaxRpcVersion() {
+    return maxRpcVersion_ == null ? io.grpc.alts.internal.RpcProtocolVersions.Version.getDefaultInstance() : maxRpcVersion_;
+  }
+  /**
+   * <pre>
+   * Maximum supported RPC version.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
+   */
+  public io.grpc.alts.internal.RpcProtocolVersions.VersionOrBuilder getMaxRpcVersionOrBuilder() {
+    return getMaxRpcVersion();
+  }
+
+  public static final int MIN_RPC_VERSION_FIELD_NUMBER = 2;
+  private io.grpc.alts.internal.RpcProtocolVersions.Version minRpcVersion_;
+  /**
+   * <pre>
+   * Minimum supported RPC version.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
+   */
+  public boolean hasMinRpcVersion() {
+    return minRpcVersion_ != null;
+  }
+  /**
+   * <pre>
+   * Minimum supported RPC version.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
+   */
+  public io.grpc.alts.internal.RpcProtocolVersions.Version getMinRpcVersion() {
+    return minRpcVersion_ == null ? io.grpc.alts.internal.RpcProtocolVersions.Version.getDefaultInstance() : minRpcVersion_;
+  }
+  /**
+   * <pre>
+   * Minimum supported RPC version.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
+   */
+  public io.grpc.alts.internal.RpcProtocolVersions.VersionOrBuilder getMinRpcVersionOrBuilder() {
+    return getMinRpcVersion();
+  }
+
+  private byte memoizedIsInitialized = -1;
+  public final boolean isInitialized() {
+    byte isInitialized = memoizedIsInitialized;
+    if (isInitialized == 1) return true;
+    if (isInitialized == 0) return false;
+
+    memoizedIsInitialized = 1;
+    return true;
+  }
+
+  public void writeTo(com.google.protobuf.CodedOutputStream output)
+                      throws java.io.IOException {
+    if (maxRpcVersion_ != null) {
+      output.writeMessage(1, getMaxRpcVersion());
+    }
+    if (minRpcVersion_ != null) {
+      output.writeMessage(2, getMinRpcVersion());
+    }
+    unknownFields.writeTo(output);
+  }
+
+  public int getSerializedSize() {
+    int size = memoizedSize;
+    if (size != -1) return size;
+
+    size = 0;
+    if (maxRpcVersion_ != null) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeMessageSize(1, getMaxRpcVersion());
+    }
+    if (minRpcVersion_ != null) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeMessageSize(2, getMinRpcVersion());
+    }
+    size += unknownFields.getSerializedSize();
+    memoizedSize = size;
+    return size;
+  }
+
+  @java.lang.Override
+  public boolean equals(final java.lang.Object obj) {
+    if (obj == this) {
+     return true;
+    }
+    if (!(obj instanceof io.grpc.alts.internal.RpcProtocolVersions)) {
+      return super.equals(obj);
+    }
+    io.grpc.alts.internal.RpcProtocolVersions other = (io.grpc.alts.internal.RpcProtocolVersions) obj;
+
+    boolean result = true;
+    result = result && (hasMaxRpcVersion() == other.hasMaxRpcVersion());
+    if (hasMaxRpcVersion()) {
+      result = result && getMaxRpcVersion()
+          .equals(other.getMaxRpcVersion());
+    }
+    result = result && (hasMinRpcVersion() == other.hasMinRpcVersion());
+    if (hasMinRpcVersion()) {
+      result = result && getMinRpcVersion()
+          .equals(other.getMinRpcVersion());
+    }
+    result = result && unknownFields.equals(other.unknownFields);
+    return result;
+  }
+
+  @java.lang.Override
+  public int hashCode() {
+    if (memoizedHashCode != 0) {
+      return memoizedHashCode;
+    }
+    int hash = 41;
+    hash = (19 * hash) + getDescriptor().hashCode();
+    if (hasMaxRpcVersion()) {
+      hash = (37 * hash) + MAX_RPC_VERSION_FIELD_NUMBER;
+      hash = (53 * hash) + getMaxRpcVersion().hashCode();
+    }
+    if (hasMinRpcVersion()) {
+      hash = (37 * hash) + MIN_RPC_VERSION_FIELD_NUMBER;
+      hash = (53 * hash) + getMinRpcVersion().hashCode();
+    }
+    hash = (29 * hash) + unknownFields.hashCode();
+    memoizedHashCode = hash;
+    return hash;
+  }
+
+  public static io.grpc.alts.internal.RpcProtocolVersions parseFrom(
+      java.nio.ByteBuffer data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.RpcProtocolVersions parseFrom(
+      java.nio.ByteBuffer data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.RpcProtocolVersions parseFrom(
+      com.google.protobuf.ByteString data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.RpcProtocolVersions parseFrom(
+      com.google.protobuf.ByteString data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.RpcProtocolVersions parseFrom(byte[] data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.RpcProtocolVersions parseFrom(
+      byte[] data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.RpcProtocolVersions parseFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.RpcProtocolVersions parseFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.RpcProtocolVersions parseDelimitedFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.RpcProtocolVersions parseDelimitedFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.RpcProtocolVersions parseFrom(
+      com.google.protobuf.CodedInputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.RpcProtocolVersions parseFrom(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+
+  public Builder newBuilderForType() { return newBuilder(); }
+  public static Builder newBuilder() {
+    return DEFAULT_INSTANCE.toBuilder();
+  }
+  public static Builder newBuilder(io.grpc.alts.internal.RpcProtocolVersions prototype) {
+    return DEFAULT_INSTANCE.toBuilder().mergeFrom(prototype);
+  }
+  public Builder toBuilder() {
+    return this == DEFAULT_INSTANCE
+        ? new Builder() : new Builder().mergeFrom(this);
+  }
+
+  @java.lang.Override
+  protected Builder newBuilderForType(
+      com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+    Builder builder = new Builder(parent);
+    return builder;
+  }
+  /**
+   * <pre>
+   * Max and min supported RPC protocol versions.
+   * </pre>
+   *
+   * Protobuf type {@code grpc.gcp.RpcProtocolVersions}
+   */
+  public static final class Builder extends
+      com.google.protobuf.GeneratedMessageV3.Builder<Builder> implements
+      // @@protoc_insertion_point(builder_implements:grpc.gcp.RpcProtocolVersions)
+      io.grpc.alts.internal.RpcProtocolVersionsOrBuilder {
+    public static final com.google.protobuf.Descriptors.Descriptor
+        getDescriptor() {
+      return io.grpc.alts.internal.TransportSecurityCommonProto.internal_static_grpc_gcp_RpcProtocolVersions_descriptor;
+    }
+
+    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+        internalGetFieldAccessorTable() {
+      return io.grpc.alts.internal.TransportSecurityCommonProto.internal_static_grpc_gcp_RpcProtocolVersions_fieldAccessorTable
+          .ensureFieldAccessorsInitialized(
+              io.grpc.alts.internal.RpcProtocolVersions.class, io.grpc.alts.internal.RpcProtocolVersions.Builder.class);
+    }
+
+    // Construct using io.grpc.alts.internal.RpcProtocolVersions.newBuilder()
+    private Builder() {
+      maybeForceBuilderInitialization();
+    }
+
+    private Builder(
+        com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+      super(parent);
+      maybeForceBuilderInitialization();
+    }
+    private void maybeForceBuilderInitialization() {
+      if (com.google.protobuf.GeneratedMessageV3
+              .alwaysUseFieldBuilders) {
+      }
+    }
+    public Builder clear() {
+      super.clear();
+      if (maxRpcVersionBuilder_ == null) {
+        maxRpcVersion_ = null;
+      } else {
+        maxRpcVersion_ = null;
+        maxRpcVersionBuilder_ = null;
+      }
+      if (minRpcVersionBuilder_ == null) {
+        minRpcVersion_ = null;
+      } else {
+        minRpcVersion_ = null;
+        minRpcVersionBuilder_ = null;
+      }
+      return this;
+    }
+
+    public com.google.protobuf.Descriptors.Descriptor
+        getDescriptorForType() {
+      return io.grpc.alts.internal.TransportSecurityCommonProto.internal_static_grpc_gcp_RpcProtocolVersions_descriptor;
+    }
+
+    public io.grpc.alts.internal.RpcProtocolVersions getDefaultInstanceForType() {
+      return io.grpc.alts.internal.RpcProtocolVersions.getDefaultInstance();
+    }
+
+    public io.grpc.alts.internal.RpcProtocolVersions build() {
+      io.grpc.alts.internal.RpcProtocolVersions result = buildPartial();
+      if (!result.isInitialized()) {
+        throw newUninitializedMessageException(result);
+      }
+      return result;
+    }
+
+    public io.grpc.alts.internal.RpcProtocolVersions buildPartial() {
+      io.grpc.alts.internal.RpcProtocolVersions result = new io.grpc.alts.internal.RpcProtocolVersions(this);
+      if (maxRpcVersionBuilder_ == null) {
+        result.maxRpcVersion_ = maxRpcVersion_;
+      } else {
+        result.maxRpcVersion_ = maxRpcVersionBuilder_.build();
+      }
+      if (minRpcVersionBuilder_ == null) {
+        result.minRpcVersion_ = minRpcVersion_;
+      } else {
+        result.minRpcVersion_ = minRpcVersionBuilder_.build();
+      }
+      onBuilt();
+      return result;
+    }
+
+    public Builder clone() {
+      return (Builder) super.clone();
+    }
+    public Builder setField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.setField(field, value);
+    }
+    public Builder clearField(
+        com.google.protobuf.Descriptors.FieldDescriptor field) {
+      return (Builder) super.clearField(field);
+    }
+    public Builder clearOneof(
+        com.google.protobuf.Descriptors.OneofDescriptor oneof) {
+      return (Builder) super.clearOneof(oneof);
+    }
+    public Builder setRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        int index, java.lang.Object value) {
+      return (Builder) super.setRepeatedField(field, index, value);
+    }
+    public Builder addRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.addRepeatedField(field, value);
+    }
+    public Builder mergeFrom(com.google.protobuf.Message other) {
+      if (other instanceof io.grpc.alts.internal.RpcProtocolVersions) {
+        return mergeFrom((io.grpc.alts.internal.RpcProtocolVersions)other);
+      } else {
+        super.mergeFrom(other);
+        return this;
+      }
+    }
+
+    public Builder mergeFrom(io.grpc.alts.internal.RpcProtocolVersions other) {
+      if (other == io.grpc.alts.internal.RpcProtocolVersions.getDefaultInstance()) return this;
+      if (other.hasMaxRpcVersion()) {
+        mergeMaxRpcVersion(other.getMaxRpcVersion());
+      }
+      if (other.hasMinRpcVersion()) {
+        mergeMinRpcVersion(other.getMinRpcVersion());
+      }
+      this.mergeUnknownFields(other.unknownFields);
+      onChanged();
+      return this;
+    }
+
+    public final boolean isInitialized() {
+      return true;
+    }
+
+    public Builder mergeFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      io.grpc.alts.internal.RpcProtocolVersions parsedMessage = null;
+      try {
+        parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);
+      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+        parsedMessage = (io.grpc.alts.internal.RpcProtocolVersions) e.getUnfinishedMessage();
+        throw e.unwrapIOException();
+      } finally {
+        if (parsedMessage != null) {
+          mergeFrom(parsedMessage);
+        }
+      }
+      return this;
+    }
+
+    private io.grpc.alts.internal.RpcProtocolVersions.Version maxRpcVersion_ = null;
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.RpcProtocolVersions.Version, io.grpc.alts.internal.RpcProtocolVersions.Version.Builder, io.grpc.alts.internal.RpcProtocolVersions.VersionOrBuilder> maxRpcVersionBuilder_;
+    /**
+     * <pre>
+     * Maximum supported RPC version.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
+     */
+    public boolean hasMaxRpcVersion() {
+      return maxRpcVersionBuilder_ != null || maxRpcVersion_ != null;
+    }
+    /**
+     * <pre>
+     * Maximum supported RPC version.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
+     */
+    public io.grpc.alts.internal.RpcProtocolVersions.Version getMaxRpcVersion() {
+      if (maxRpcVersionBuilder_ == null) {
+        return maxRpcVersion_ == null ? io.grpc.alts.internal.RpcProtocolVersions.Version.getDefaultInstance() : maxRpcVersion_;
+      } else {
+        return maxRpcVersionBuilder_.getMessage();
+      }
+    }
+    /**
+     * <pre>
+     * Maximum supported RPC version.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
+     */
+    public Builder setMaxRpcVersion(io.grpc.alts.internal.RpcProtocolVersions.Version value) {
+      if (maxRpcVersionBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        maxRpcVersion_ = value;
+        onChanged();
+      } else {
+        maxRpcVersionBuilder_.setMessage(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * Maximum supported RPC version.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
+     */
+    public Builder setMaxRpcVersion(
+        io.grpc.alts.internal.RpcProtocolVersions.Version.Builder builderForValue) {
+      if (maxRpcVersionBuilder_ == null) {
+        maxRpcVersion_ = builderForValue.build();
+        onChanged();
+      } else {
+        maxRpcVersionBuilder_.setMessage(builderForValue.build());
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * Maximum supported RPC version.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
+     */
+    public Builder mergeMaxRpcVersion(io.grpc.alts.internal.RpcProtocolVersions.Version value) {
+      if (maxRpcVersionBuilder_ == null) {
+        if (maxRpcVersion_ != null) {
+          maxRpcVersion_ =
+            io.grpc.alts.internal.RpcProtocolVersions.Version.newBuilder(maxRpcVersion_).mergeFrom(value).buildPartial();
+        } else {
+          maxRpcVersion_ = value;
+        }
+        onChanged();
+      } else {
+        maxRpcVersionBuilder_.mergeFrom(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * Maximum supported RPC version.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
+     */
+    public Builder clearMaxRpcVersion() {
+      if (maxRpcVersionBuilder_ == null) {
+        maxRpcVersion_ = null;
+        onChanged();
+      } else {
+        maxRpcVersion_ = null;
+        maxRpcVersionBuilder_ = null;
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * Maximum supported RPC version.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
+     */
+    public io.grpc.alts.internal.RpcProtocolVersions.Version.Builder getMaxRpcVersionBuilder() {
+      
+      onChanged();
+      return getMaxRpcVersionFieldBuilder().getBuilder();
+    }
+    /**
+     * <pre>
+     * Maximum supported RPC version.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
+     */
+    public io.grpc.alts.internal.RpcProtocolVersions.VersionOrBuilder getMaxRpcVersionOrBuilder() {
+      if (maxRpcVersionBuilder_ != null) {
+        return maxRpcVersionBuilder_.getMessageOrBuilder();
+      } else {
+        return maxRpcVersion_ == null ?
+            io.grpc.alts.internal.RpcProtocolVersions.Version.getDefaultInstance() : maxRpcVersion_;
+      }
+    }
+    /**
+     * <pre>
+     * Maximum supported RPC version.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
+     */
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.RpcProtocolVersions.Version, io.grpc.alts.internal.RpcProtocolVersions.Version.Builder, io.grpc.alts.internal.RpcProtocolVersions.VersionOrBuilder> 
+        getMaxRpcVersionFieldBuilder() {
+      if (maxRpcVersionBuilder_ == null) {
+        maxRpcVersionBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
+            io.grpc.alts.internal.RpcProtocolVersions.Version, io.grpc.alts.internal.RpcProtocolVersions.Version.Builder, io.grpc.alts.internal.RpcProtocolVersions.VersionOrBuilder>(
+                getMaxRpcVersion(),
+                getParentForChildren(),
+                isClean());
+        maxRpcVersion_ = null;
+      }
+      return maxRpcVersionBuilder_;
+    }
+
+    private io.grpc.alts.internal.RpcProtocolVersions.Version minRpcVersion_ = null;
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.RpcProtocolVersions.Version, io.grpc.alts.internal.RpcProtocolVersions.Version.Builder, io.grpc.alts.internal.RpcProtocolVersions.VersionOrBuilder> minRpcVersionBuilder_;
+    /**
+     * <pre>
+     * Minimum supported RPC version.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
+     */
+    public boolean hasMinRpcVersion() {
+      return minRpcVersionBuilder_ != null || minRpcVersion_ != null;
+    }
+    /**
+     * <pre>
+     * Minimum supported RPC version.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
+     */
+    public io.grpc.alts.internal.RpcProtocolVersions.Version getMinRpcVersion() {
+      if (minRpcVersionBuilder_ == null) {
+        return minRpcVersion_ == null ? io.grpc.alts.internal.RpcProtocolVersions.Version.getDefaultInstance() : minRpcVersion_;
+      } else {
+        return minRpcVersionBuilder_.getMessage();
+      }
+    }
+    /**
+     * <pre>
+     * Minimum supported RPC version.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
+     */
+    public Builder setMinRpcVersion(io.grpc.alts.internal.RpcProtocolVersions.Version value) {
+      if (minRpcVersionBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        minRpcVersion_ = value;
+        onChanged();
+      } else {
+        minRpcVersionBuilder_.setMessage(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * Minimum supported RPC version.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
+     */
+    public Builder setMinRpcVersion(
+        io.grpc.alts.internal.RpcProtocolVersions.Version.Builder builderForValue) {
+      if (minRpcVersionBuilder_ == null) {
+        minRpcVersion_ = builderForValue.build();
+        onChanged();
+      } else {
+        minRpcVersionBuilder_.setMessage(builderForValue.build());
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * Minimum supported RPC version.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
+     */
+    public Builder mergeMinRpcVersion(io.grpc.alts.internal.RpcProtocolVersions.Version value) {
+      if (minRpcVersionBuilder_ == null) {
+        if (minRpcVersion_ != null) {
+          minRpcVersion_ =
+            io.grpc.alts.internal.RpcProtocolVersions.Version.newBuilder(minRpcVersion_).mergeFrom(value).buildPartial();
+        } else {
+          minRpcVersion_ = value;
+        }
+        onChanged();
+      } else {
+        minRpcVersionBuilder_.mergeFrom(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * Minimum supported RPC version.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
+     */
+    public Builder clearMinRpcVersion() {
+      if (minRpcVersionBuilder_ == null) {
+        minRpcVersion_ = null;
+        onChanged();
+      } else {
+        minRpcVersion_ = null;
+        minRpcVersionBuilder_ = null;
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * Minimum supported RPC version.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
+     */
+    public io.grpc.alts.internal.RpcProtocolVersions.Version.Builder getMinRpcVersionBuilder() {
+      
+      onChanged();
+      return getMinRpcVersionFieldBuilder().getBuilder();
+    }
+    /**
+     * <pre>
+     * Minimum supported RPC version.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
+     */
+    public io.grpc.alts.internal.RpcProtocolVersions.VersionOrBuilder getMinRpcVersionOrBuilder() {
+      if (minRpcVersionBuilder_ != null) {
+        return minRpcVersionBuilder_.getMessageOrBuilder();
+      } else {
+        return minRpcVersion_ == null ?
+            io.grpc.alts.internal.RpcProtocolVersions.Version.getDefaultInstance() : minRpcVersion_;
+      }
+    }
+    /**
+     * <pre>
+     * Minimum supported RPC version.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
+     */
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.RpcProtocolVersions.Version, io.grpc.alts.internal.RpcProtocolVersions.Version.Builder, io.grpc.alts.internal.RpcProtocolVersions.VersionOrBuilder> 
+        getMinRpcVersionFieldBuilder() {
+      if (minRpcVersionBuilder_ == null) {
+        minRpcVersionBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
+            io.grpc.alts.internal.RpcProtocolVersions.Version, io.grpc.alts.internal.RpcProtocolVersions.Version.Builder, io.grpc.alts.internal.RpcProtocolVersions.VersionOrBuilder>(
+                getMinRpcVersion(),
+                getParentForChildren(),
+                isClean());
+        minRpcVersion_ = null;
+      }
+      return minRpcVersionBuilder_;
+    }
+    public final Builder setUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.setUnknownFieldsProto3(unknownFields);
+    }
+
+    public final Builder mergeUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.mergeUnknownFields(unknownFields);
+    }
+
+
+    // @@protoc_insertion_point(builder_scope:grpc.gcp.RpcProtocolVersions)
+  }
+
+  // @@protoc_insertion_point(class_scope:grpc.gcp.RpcProtocolVersions)
+  private static final io.grpc.alts.internal.RpcProtocolVersions DEFAULT_INSTANCE;
+  static {
+    DEFAULT_INSTANCE = new io.grpc.alts.internal.RpcProtocolVersions();
+  }
+
+  public static io.grpc.alts.internal.RpcProtocolVersions getDefaultInstance() {
+    return DEFAULT_INSTANCE;
+  }
+
+  private static final com.google.protobuf.Parser<RpcProtocolVersions>
+      PARSER = new com.google.protobuf.AbstractParser<RpcProtocolVersions>() {
+    public RpcProtocolVersions parsePartialFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return new RpcProtocolVersions(input, extensionRegistry);
+    }
+  };
+
+  public static com.google.protobuf.Parser<RpcProtocolVersions> parser() {
+    return PARSER;
+  }
+
+  @java.lang.Override
+  public com.google.protobuf.Parser<RpcProtocolVersions> getParserForType() {
+    return PARSER;
+  }
+
+  public io.grpc.alts.internal.RpcProtocolVersions getDefaultInstanceForType() {
+    return DEFAULT_INSTANCE;
+  }
+
+}
+
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/RpcProtocolVersionsOrBuilder.java b/alts/src/generated/main/java/io/grpc/alts/internal/RpcProtocolVersionsOrBuilder.java
new file mode 100644
index 0000000000..774a6cc571
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/RpcProtocolVersionsOrBuilder.java
@@ -0,0 +1,59 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/transport_security_common.proto
+
+package io.grpc.alts.internal;
+
+public interface RpcProtocolVersionsOrBuilder extends
+    // @@protoc_insertion_point(interface_extends:grpc.gcp.RpcProtocolVersions)
+    com.google.protobuf.MessageOrBuilder {
+
+  /**
+   * <pre>
+   * Maximum supported RPC version.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
+   */
+  boolean hasMaxRpcVersion();
+  /**
+   * <pre>
+   * Maximum supported RPC version.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
+   */
+  io.grpc.alts.internal.RpcProtocolVersions.Version getMaxRpcVersion();
+  /**
+   * <pre>
+   * Maximum supported RPC version.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
+   */
+  io.grpc.alts.internal.RpcProtocolVersions.VersionOrBuilder getMaxRpcVersionOrBuilder();
+
+  /**
+   * <pre>
+   * Minimum supported RPC version.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
+   */
+  boolean hasMinRpcVersion();
+  /**
+   * <pre>
+   * Minimum supported RPC version.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
+   */
+  io.grpc.alts.internal.RpcProtocolVersions.Version getMinRpcVersion();
+  /**
+   * <pre>
+   * Minimum supported RPC version.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
+   */
+  io.grpc.alts.internal.RpcProtocolVersions.VersionOrBuilder getMinRpcVersionOrBuilder();
+}
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/SecurityLevel.java b/alts/src/generated/main/java/io/grpc/alts/internal/SecurityLevel.java
new file mode 100644
index 0000000000..aee2108f8a
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/SecurityLevel.java
@@ -0,0 +1,117 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/transport_security_common.proto
+
+package io.grpc.alts.internal;
+
+/**
+ * <pre>
+ * The security level of the created channel. The list is sorted in increasing
+ * level of security. This order must always be maintained.
+ * </pre>
+ *
+ * Protobuf enum {@code grpc.gcp.SecurityLevel}
+ */
+public enum SecurityLevel
+    implements com.google.protobuf.ProtocolMessageEnum {
+  /**
+   * <code>SECURITY_NONE = 0;</code>
+   */
+  SECURITY_NONE(0),
+  /**
+   * <code>INTEGRITY_ONLY = 1;</code>
+   */
+  INTEGRITY_ONLY(1),
+  /**
+   * <code>INTEGRITY_AND_PRIVACY = 2;</code>
+   */
+  INTEGRITY_AND_PRIVACY(2),
+  UNRECOGNIZED(-1),
+  ;
+
+  /**
+   * <code>SECURITY_NONE = 0;</code>
+   */
+  public static final int SECURITY_NONE_VALUE = 0;
+  /**
+   * <code>INTEGRITY_ONLY = 1;</code>
+   */
+  public static final int INTEGRITY_ONLY_VALUE = 1;
+  /**
+   * <code>INTEGRITY_AND_PRIVACY = 2;</code>
+   */
+  public static final int INTEGRITY_AND_PRIVACY_VALUE = 2;
+
+
+  public final int getNumber() {
+    if (this == UNRECOGNIZED) {
+      throw new java.lang.IllegalArgumentException(
+          "Can't get the number of an unknown enum value.");
+    }
+    return value;
+  }
+
+  /**
+   * @deprecated Use {@link #forNumber(int)} instead.
+   */
+  @java.lang.Deprecated
+  public static SecurityLevel valueOf(int value) {
+    return forNumber(value);
+  }
+
+  public static SecurityLevel forNumber(int value) {
+    switch (value) {
+      case 0: return SECURITY_NONE;
+      case 1: return INTEGRITY_ONLY;
+      case 2: return INTEGRITY_AND_PRIVACY;
+      default: return null;
+    }
+  }
+
+  public static com.google.protobuf.Internal.EnumLiteMap<SecurityLevel>
+      internalGetValueMap() {
+    return internalValueMap;
+  }
+  private static final com.google.protobuf.Internal.EnumLiteMap<
+      SecurityLevel> internalValueMap =
+        new com.google.protobuf.Internal.EnumLiteMap<SecurityLevel>() {
+          public SecurityLevel findValueByNumber(int number) {
+            return SecurityLevel.forNumber(number);
+          }
+        };
+
+  public final com.google.protobuf.Descriptors.EnumValueDescriptor
+      getValueDescriptor() {
+    return getDescriptor().getValues().get(ordinal());
+  }
+  public final com.google.protobuf.Descriptors.EnumDescriptor
+      getDescriptorForType() {
+    return getDescriptor();
+  }
+  public static final com.google.protobuf.Descriptors.EnumDescriptor
+      getDescriptor() {
+    return io.grpc.alts.internal.TransportSecurityCommonProto.getDescriptor().getEnumTypes().get(0);
+  }
+
+  private static final SecurityLevel[] VALUES = values();
+
+  public static SecurityLevel valueOf(
+      com.google.protobuf.Descriptors.EnumValueDescriptor desc) {
+    if (desc.getType() != getDescriptor()) {
+      throw new java.lang.IllegalArgumentException(
+        "EnumValueDescriptor is not for this type.");
+    }
+    if (desc.getIndex() == -1) {
+      return UNRECOGNIZED;
+    }
+    return VALUES[desc.getIndex()];
+  }
+
+  private final int value;
+
+  private SecurityLevel(int value) {
+    this.value = value;
+  }
+
+  // @@protoc_insertion_point(enum_scope:grpc.gcp.SecurityLevel)
+}
+
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/ServerHandshakeParameters.java b/alts/src/generated/main/java/io/grpc/alts/internal/ServerHandshakeParameters.java
new file mode 100644
index 0000000000..3c733c6dd5
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/ServerHandshakeParameters.java
@@ -0,0 +1,1084 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+/**
+ * Protobuf type {@code grpc.gcp.ServerHandshakeParameters}
+ */
+public  final class ServerHandshakeParameters extends
+    com.google.protobuf.GeneratedMessageV3 implements
+    // @@protoc_insertion_point(message_implements:grpc.gcp.ServerHandshakeParameters)
+    ServerHandshakeParametersOrBuilder {
+private static final long serialVersionUID = 0L;
+  // Use ServerHandshakeParameters.newBuilder() to construct.
+  private ServerHandshakeParameters(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
+    super(builder);
+  }
+  private ServerHandshakeParameters() {
+    recordProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
+    localIdentities_ = java.util.Collections.emptyList();
+  }
+
+  @java.lang.Override
+  public final com.google.protobuf.UnknownFieldSet
+  getUnknownFields() {
+    return this.unknownFields;
+  }
+  private ServerHandshakeParameters(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    this();
+    if (extensionRegistry == null) {
+      throw new java.lang.NullPointerException();
+    }
+    int mutable_bitField0_ = 0;
+    com.google.protobuf.UnknownFieldSet.Builder unknownFields =
+        com.google.protobuf.UnknownFieldSet.newBuilder();
+    try {
+      boolean done = false;
+      while (!done) {
+        int tag = input.readTag();
+        switch (tag) {
+          case 0:
+            done = true;
+            break;
+          default: {
+            if (!parseUnknownFieldProto3(
+                input, unknownFields, extensionRegistry, tag)) {
+              done = true;
+            }
+            break;
+          }
+          case 10: {
+            java.lang.String s = input.readStringRequireUtf8();
+            if (!((mutable_bitField0_ & 0x00000001) == 0x00000001)) {
+              recordProtocols_ = new com.google.protobuf.LazyStringArrayList();
+              mutable_bitField0_ |= 0x00000001;
+            }
+            recordProtocols_.add(s);
+            break;
+          }
+          case 18: {
+            if (!((mutable_bitField0_ & 0x00000002) == 0x00000002)) {
+              localIdentities_ = new java.util.ArrayList<io.grpc.alts.internal.Identity>();
+              mutable_bitField0_ |= 0x00000002;
+            }
+            localIdentities_.add(
+                input.readMessage(io.grpc.alts.internal.Identity.parser(), extensionRegistry));
+            break;
+          }
+        }
+      }
+    } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+      throw e.setUnfinishedMessage(this);
+    } catch (java.io.IOException e) {
+      throw new com.google.protobuf.InvalidProtocolBufferException(
+          e).setUnfinishedMessage(this);
+    } finally {
+      if (((mutable_bitField0_ & 0x00000001) == 0x00000001)) {
+        recordProtocols_ = recordProtocols_.getUnmodifiableView();
+      }
+      if (((mutable_bitField0_ & 0x00000002) == 0x00000002)) {
+        localIdentities_ = java.util.Collections.unmodifiableList(localIdentities_);
+      }
+      this.unknownFields = unknownFields.build();
+      makeExtensionsImmutable();
+    }
+  }
+  public static final com.google.protobuf.Descriptors.Descriptor
+      getDescriptor() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_ServerHandshakeParameters_descriptor;
+  }
+
+  protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internalGetFieldAccessorTable() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_ServerHandshakeParameters_fieldAccessorTable
+        .ensureFieldAccessorsInitialized(
+            io.grpc.alts.internal.ServerHandshakeParameters.class, io.grpc.alts.internal.ServerHandshakeParameters.Builder.class);
+  }
+
+  public static final int RECORD_PROTOCOLS_FIELD_NUMBER = 1;
+  private com.google.protobuf.LazyStringList recordProtocols_;
+  /**
+   * <pre>
+   * The record protocols supported by the server, e.g.,
+   * "ALTSRP_GCM_AES128".
+   * </pre>
+   *
+   * <code>repeated string record_protocols = 1;</code>
+   */
+  public com.google.protobuf.ProtocolStringList
+      getRecordProtocolsList() {
+    return recordProtocols_;
+  }
+  /**
+   * <pre>
+   * The record protocols supported by the server, e.g.,
+   * "ALTSRP_GCM_AES128".
+   * </pre>
+   *
+   * <code>repeated string record_protocols = 1;</code>
+   */
+  public int getRecordProtocolsCount() {
+    return recordProtocols_.size();
+  }
+  /**
+   * <pre>
+   * The record protocols supported by the server, e.g.,
+   * "ALTSRP_GCM_AES128".
+   * </pre>
+   *
+   * <code>repeated string record_protocols = 1;</code>
+   */
+  public java.lang.String getRecordProtocols(int index) {
+    return recordProtocols_.get(index);
+  }
+  /**
+   * <pre>
+   * The record protocols supported by the server, e.g.,
+   * "ALTSRP_GCM_AES128".
+   * </pre>
+   *
+   * <code>repeated string record_protocols = 1;</code>
+   */
+  public com.google.protobuf.ByteString
+      getRecordProtocolsBytes(int index) {
+    return recordProtocols_.getByteString(index);
+  }
+
+  public static final int LOCAL_IDENTITIES_FIELD_NUMBER = 2;
+  private java.util.List<io.grpc.alts.internal.Identity> localIdentities_;
+  /**
+   * <pre>
+   * (Optional) A list of local identities supported by the server, if
+   * specified. Otherwise, the handshaker chooses a default local identity.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+   */
+  public java.util.List<io.grpc.alts.internal.Identity> getLocalIdentitiesList() {
+    return localIdentities_;
+  }
+  /**
+   * <pre>
+   * (Optional) A list of local identities supported by the server, if
+   * specified. Otherwise, the handshaker chooses a default local identity.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+   */
+  public java.util.List<? extends io.grpc.alts.internal.IdentityOrBuilder> 
+      getLocalIdentitiesOrBuilderList() {
+    return localIdentities_;
+  }
+  /**
+   * <pre>
+   * (Optional) A list of local identities supported by the server, if
+   * specified. Otherwise, the handshaker chooses a default local identity.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+   */
+  public int getLocalIdentitiesCount() {
+    return localIdentities_.size();
+  }
+  /**
+   * <pre>
+   * (Optional) A list of local identities supported by the server, if
+   * specified. Otherwise, the handshaker chooses a default local identity.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+   */
+  public io.grpc.alts.internal.Identity getLocalIdentities(int index) {
+    return localIdentities_.get(index);
+  }
+  /**
+   * <pre>
+   * (Optional) A list of local identities supported by the server, if
+   * specified. Otherwise, the handshaker chooses a default local identity.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+   */
+  public io.grpc.alts.internal.IdentityOrBuilder getLocalIdentitiesOrBuilder(
+      int index) {
+    return localIdentities_.get(index);
+  }
+
+  private byte memoizedIsInitialized = -1;
+  public final boolean isInitialized() {
+    byte isInitialized = memoizedIsInitialized;
+    if (isInitialized == 1) return true;
+    if (isInitialized == 0) return false;
+
+    memoizedIsInitialized = 1;
+    return true;
+  }
+
+  public void writeTo(com.google.protobuf.CodedOutputStream output)
+                      throws java.io.IOException {
+    for (int i = 0; i < recordProtocols_.size(); i++) {
+      com.google.protobuf.GeneratedMessageV3.writeString(output, 1, recordProtocols_.getRaw(i));
+    }
+    for (int i = 0; i < localIdentities_.size(); i++) {
+      output.writeMessage(2, localIdentities_.get(i));
+    }
+    unknownFields.writeTo(output);
+  }
+
+  public int getSerializedSize() {
+    int size = memoizedSize;
+    if (size != -1) return size;
+
+    size = 0;
+    {
+      int dataSize = 0;
+      for (int i = 0; i < recordProtocols_.size(); i++) {
+        dataSize += computeStringSizeNoTag(recordProtocols_.getRaw(i));
+      }
+      size += dataSize;
+      size += 1 * getRecordProtocolsList().size();
+    }
+    for (int i = 0; i < localIdentities_.size(); i++) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeMessageSize(2, localIdentities_.get(i));
+    }
+    size += unknownFields.getSerializedSize();
+    memoizedSize = size;
+    return size;
+  }
+
+  @java.lang.Override
+  public boolean equals(final java.lang.Object obj) {
+    if (obj == this) {
+     return true;
+    }
+    if (!(obj instanceof io.grpc.alts.internal.ServerHandshakeParameters)) {
+      return super.equals(obj);
+    }
+    io.grpc.alts.internal.ServerHandshakeParameters other = (io.grpc.alts.internal.ServerHandshakeParameters) obj;
+
+    boolean result = true;
+    result = result && getRecordProtocolsList()
+        .equals(other.getRecordProtocolsList());
+    result = result && getLocalIdentitiesList()
+        .equals(other.getLocalIdentitiesList());
+    result = result && unknownFields.equals(other.unknownFields);
+    return result;
+  }
+
+  @java.lang.Override
+  public int hashCode() {
+    if (memoizedHashCode != 0) {
+      return memoizedHashCode;
+    }
+    int hash = 41;
+    hash = (19 * hash) + getDescriptor().hashCode();
+    if (getRecordProtocolsCount() > 0) {
+      hash = (37 * hash) + RECORD_PROTOCOLS_FIELD_NUMBER;
+      hash = (53 * hash) + getRecordProtocolsList().hashCode();
+    }
+    if (getLocalIdentitiesCount() > 0) {
+      hash = (37 * hash) + LOCAL_IDENTITIES_FIELD_NUMBER;
+      hash = (53 * hash) + getLocalIdentitiesList().hashCode();
+    }
+    hash = (29 * hash) + unknownFields.hashCode();
+    memoizedHashCode = hash;
+    return hash;
+  }
+
+  public static io.grpc.alts.internal.ServerHandshakeParameters parseFrom(
+      java.nio.ByteBuffer data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.ServerHandshakeParameters parseFrom(
+      java.nio.ByteBuffer data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.ServerHandshakeParameters parseFrom(
+      com.google.protobuf.ByteString data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.ServerHandshakeParameters parseFrom(
+      com.google.protobuf.ByteString data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.ServerHandshakeParameters parseFrom(byte[] data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.ServerHandshakeParameters parseFrom(
+      byte[] data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.ServerHandshakeParameters parseFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.ServerHandshakeParameters parseFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.ServerHandshakeParameters parseDelimitedFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.ServerHandshakeParameters parseDelimitedFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.ServerHandshakeParameters parseFrom(
+      com.google.protobuf.CodedInputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.ServerHandshakeParameters parseFrom(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+
+  public Builder newBuilderForType() { return newBuilder(); }
+  public static Builder newBuilder() {
+    return DEFAULT_INSTANCE.toBuilder();
+  }
+  public static Builder newBuilder(io.grpc.alts.internal.ServerHandshakeParameters prototype) {
+    return DEFAULT_INSTANCE.toBuilder().mergeFrom(prototype);
+  }
+  public Builder toBuilder() {
+    return this == DEFAULT_INSTANCE
+        ? new Builder() : new Builder().mergeFrom(this);
+  }
+
+  @java.lang.Override
+  protected Builder newBuilderForType(
+      com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+    Builder builder = new Builder(parent);
+    return builder;
+  }
+  /**
+   * Protobuf type {@code grpc.gcp.ServerHandshakeParameters}
+   */
+  public static final class Builder extends
+      com.google.protobuf.GeneratedMessageV3.Builder<Builder> implements
+      // @@protoc_insertion_point(builder_implements:grpc.gcp.ServerHandshakeParameters)
+      io.grpc.alts.internal.ServerHandshakeParametersOrBuilder {
+    public static final com.google.protobuf.Descriptors.Descriptor
+        getDescriptor() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_ServerHandshakeParameters_descriptor;
+    }
+
+    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+        internalGetFieldAccessorTable() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_ServerHandshakeParameters_fieldAccessorTable
+          .ensureFieldAccessorsInitialized(
+              io.grpc.alts.internal.ServerHandshakeParameters.class, io.grpc.alts.internal.ServerHandshakeParameters.Builder.class);
+    }
+
+    // Construct using io.grpc.alts.internal.ServerHandshakeParameters.newBuilder()
+    private Builder() {
+      maybeForceBuilderInitialization();
+    }
+
+    private Builder(
+        com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+      super(parent);
+      maybeForceBuilderInitialization();
+    }
+    private void maybeForceBuilderInitialization() {
+      if (com.google.protobuf.GeneratedMessageV3
+              .alwaysUseFieldBuilders) {
+        getLocalIdentitiesFieldBuilder();
+      }
+    }
+    public Builder clear() {
+      super.clear();
+      recordProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
+      bitField0_ = (bitField0_ & ~0x00000001);
+      if (localIdentitiesBuilder_ == null) {
+        localIdentities_ = java.util.Collections.emptyList();
+        bitField0_ = (bitField0_ & ~0x00000002);
+      } else {
+        localIdentitiesBuilder_.clear();
+      }
+      return this;
+    }
+
+    public com.google.protobuf.Descriptors.Descriptor
+        getDescriptorForType() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_ServerHandshakeParameters_descriptor;
+    }
+
+    public io.grpc.alts.internal.ServerHandshakeParameters getDefaultInstanceForType() {
+      return io.grpc.alts.internal.ServerHandshakeParameters.getDefaultInstance();
+    }
+
+    public io.grpc.alts.internal.ServerHandshakeParameters build() {
+      io.grpc.alts.internal.ServerHandshakeParameters result = buildPartial();
+      if (!result.isInitialized()) {
+        throw newUninitializedMessageException(result);
+      }
+      return result;
+    }
+
+    public io.grpc.alts.internal.ServerHandshakeParameters buildPartial() {
+      io.grpc.alts.internal.ServerHandshakeParameters result = new io.grpc.alts.internal.ServerHandshakeParameters(this);
+      int from_bitField0_ = bitField0_;
+      if (((bitField0_ & 0x00000001) == 0x00000001)) {
+        recordProtocols_ = recordProtocols_.getUnmodifiableView();
+        bitField0_ = (bitField0_ & ~0x00000001);
+      }
+      result.recordProtocols_ = recordProtocols_;
+      if (localIdentitiesBuilder_ == null) {
+        if (((bitField0_ & 0x00000002) == 0x00000002)) {
+          localIdentities_ = java.util.Collections.unmodifiableList(localIdentities_);
+          bitField0_ = (bitField0_ & ~0x00000002);
+        }
+        result.localIdentities_ = localIdentities_;
+      } else {
+        result.localIdentities_ = localIdentitiesBuilder_.build();
+      }
+      onBuilt();
+      return result;
+    }
+
+    public Builder clone() {
+      return (Builder) super.clone();
+    }
+    public Builder setField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.setField(field, value);
+    }
+    public Builder clearField(
+        com.google.protobuf.Descriptors.FieldDescriptor field) {
+      return (Builder) super.clearField(field);
+    }
+    public Builder clearOneof(
+        com.google.protobuf.Descriptors.OneofDescriptor oneof) {
+      return (Builder) super.clearOneof(oneof);
+    }
+    public Builder setRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        int index, java.lang.Object value) {
+      return (Builder) super.setRepeatedField(field, index, value);
+    }
+    public Builder addRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.addRepeatedField(field, value);
+    }
+    public Builder mergeFrom(com.google.protobuf.Message other) {
+      if (other instanceof io.grpc.alts.internal.ServerHandshakeParameters) {
+        return mergeFrom((io.grpc.alts.internal.ServerHandshakeParameters)other);
+      } else {
+        super.mergeFrom(other);
+        return this;
+      }
+    }
+
+    public Builder mergeFrom(io.grpc.alts.internal.ServerHandshakeParameters other) {
+      if (other == io.grpc.alts.internal.ServerHandshakeParameters.getDefaultInstance()) return this;
+      if (!other.recordProtocols_.isEmpty()) {
+        if (recordProtocols_.isEmpty()) {
+          recordProtocols_ = other.recordProtocols_;
+          bitField0_ = (bitField0_ & ~0x00000001);
+        } else {
+          ensureRecordProtocolsIsMutable();
+          recordProtocols_.addAll(other.recordProtocols_);
+        }
+        onChanged();
+      }
+      if (localIdentitiesBuilder_ == null) {
+        if (!other.localIdentities_.isEmpty()) {
+          if (localIdentities_.isEmpty()) {
+            localIdentities_ = other.localIdentities_;
+            bitField0_ = (bitField0_ & ~0x00000002);
+          } else {
+            ensureLocalIdentitiesIsMutable();
+            localIdentities_.addAll(other.localIdentities_);
+          }
+          onChanged();
+        }
+      } else {
+        if (!other.localIdentities_.isEmpty()) {
+          if (localIdentitiesBuilder_.isEmpty()) {
+            localIdentitiesBuilder_.dispose();
+            localIdentitiesBuilder_ = null;
+            localIdentities_ = other.localIdentities_;
+            bitField0_ = (bitField0_ & ~0x00000002);
+            localIdentitiesBuilder_ = 
+              com.google.protobuf.GeneratedMessageV3.alwaysUseFieldBuilders ?
+                 getLocalIdentitiesFieldBuilder() : null;
+          } else {
+            localIdentitiesBuilder_.addAllMessages(other.localIdentities_);
+          }
+        }
+      }
+      this.mergeUnknownFields(other.unknownFields);
+      onChanged();
+      return this;
+    }
+
+    public final boolean isInitialized() {
+      return true;
+    }
+
+    public Builder mergeFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      io.grpc.alts.internal.ServerHandshakeParameters parsedMessage = null;
+      try {
+        parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);
+      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+        parsedMessage = (io.grpc.alts.internal.ServerHandshakeParameters) e.getUnfinishedMessage();
+        throw e.unwrapIOException();
+      } finally {
+        if (parsedMessage != null) {
+          mergeFrom(parsedMessage);
+        }
+      }
+      return this;
+    }
+    private int bitField0_;
+
+    private com.google.protobuf.LazyStringList recordProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
+    private void ensureRecordProtocolsIsMutable() {
+      if (!((bitField0_ & 0x00000001) == 0x00000001)) {
+        recordProtocols_ = new com.google.protobuf.LazyStringArrayList(recordProtocols_);
+        bitField0_ |= 0x00000001;
+       }
+    }
+    /**
+     * <pre>
+     * The record protocols supported by the server, e.g.,
+     * "ALTSRP_GCM_AES128".
+     * </pre>
+     *
+     * <code>repeated string record_protocols = 1;</code>
+     */
+    public com.google.protobuf.ProtocolStringList
+        getRecordProtocolsList() {
+      return recordProtocols_.getUnmodifiableView();
+    }
+    /**
+     * <pre>
+     * The record protocols supported by the server, e.g.,
+     * "ALTSRP_GCM_AES128".
+     * </pre>
+     *
+     * <code>repeated string record_protocols = 1;</code>
+     */
+    public int getRecordProtocolsCount() {
+      return recordProtocols_.size();
+    }
+    /**
+     * <pre>
+     * The record protocols supported by the server, e.g.,
+     * "ALTSRP_GCM_AES128".
+     * </pre>
+     *
+     * <code>repeated string record_protocols = 1;</code>
+     */
+    public java.lang.String getRecordProtocols(int index) {
+      return recordProtocols_.get(index);
+    }
+    /**
+     * <pre>
+     * The record protocols supported by the server, e.g.,
+     * "ALTSRP_GCM_AES128".
+     * </pre>
+     *
+     * <code>repeated string record_protocols = 1;</code>
+     */
+    public com.google.protobuf.ByteString
+        getRecordProtocolsBytes(int index) {
+      return recordProtocols_.getByteString(index);
+    }
+    /**
+     * <pre>
+     * The record protocols supported by the server, e.g.,
+     * "ALTSRP_GCM_AES128".
+     * </pre>
+     *
+     * <code>repeated string record_protocols = 1;</code>
+     */
+    public Builder setRecordProtocols(
+        int index, java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  ensureRecordProtocolsIsMutable();
+      recordProtocols_.set(index, value);
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The record protocols supported by the server, e.g.,
+     * "ALTSRP_GCM_AES128".
+     * </pre>
+     *
+     * <code>repeated string record_protocols = 1;</code>
+     */
+    public Builder addRecordProtocols(
+        java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  ensureRecordProtocolsIsMutable();
+      recordProtocols_.add(value);
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The record protocols supported by the server, e.g.,
+     * "ALTSRP_GCM_AES128".
+     * </pre>
+     *
+     * <code>repeated string record_protocols = 1;</code>
+     */
+    public Builder addAllRecordProtocols(
+        java.lang.Iterable<java.lang.String> values) {
+      ensureRecordProtocolsIsMutable();
+      com.google.protobuf.AbstractMessageLite.Builder.addAll(
+          values, recordProtocols_);
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The record protocols supported by the server, e.g.,
+     * "ALTSRP_GCM_AES128".
+     * </pre>
+     *
+     * <code>repeated string record_protocols = 1;</code>
+     */
+    public Builder clearRecordProtocols() {
+      recordProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
+      bitField0_ = (bitField0_ & ~0x00000001);
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The record protocols supported by the server, e.g.,
+     * "ALTSRP_GCM_AES128".
+     * </pre>
+     *
+     * <code>repeated string record_protocols = 1;</code>
+     */
+    public Builder addRecordProtocolsBytes(
+        com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  checkByteStringIsUtf8(value);
+      ensureRecordProtocolsIsMutable();
+      recordProtocols_.add(value);
+      onChanged();
+      return this;
+    }
+
+    private java.util.List<io.grpc.alts.internal.Identity> localIdentities_ =
+      java.util.Collections.emptyList();
+    private void ensureLocalIdentitiesIsMutable() {
+      if (!((bitField0_ & 0x00000002) == 0x00000002)) {
+        localIdentities_ = new java.util.ArrayList<io.grpc.alts.internal.Identity>(localIdentities_);
+        bitField0_ |= 0x00000002;
+       }
+    }
+
+    private com.google.protobuf.RepeatedFieldBuilderV3<
+        io.grpc.alts.internal.Identity, io.grpc.alts.internal.Identity.Builder, io.grpc.alts.internal.IdentityOrBuilder> localIdentitiesBuilder_;
+
+    /**
+     * <pre>
+     * (Optional) A list of local identities supported by the server, if
+     * specified. Otherwise, the handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+     */
+    public java.util.List<io.grpc.alts.internal.Identity> getLocalIdentitiesList() {
+      if (localIdentitiesBuilder_ == null) {
+        return java.util.Collections.unmodifiableList(localIdentities_);
+      } else {
+        return localIdentitiesBuilder_.getMessageList();
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) A list of local identities supported by the server, if
+     * specified. Otherwise, the handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+     */
+    public int getLocalIdentitiesCount() {
+      if (localIdentitiesBuilder_ == null) {
+        return localIdentities_.size();
+      } else {
+        return localIdentitiesBuilder_.getCount();
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) A list of local identities supported by the server, if
+     * specified. Otherwise, the handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+     */
+    public io.grpc.alts.internal.Identity getLocalIdentities(int index) {
+      if (localIdentitiesBuilder_ == null) {
+        return localIdentities_.get(index);
+      } else {
+        return localIdentitiesBuilder_.getMessage(index);
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) A list of local identities supported by the server, if
+     * specified. Otherwise, the handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+     */
+    public Builder setLocalIdentities(
+        int index, io.grpc.alts.internal.Identity value) {
+      if (localIdentitiesBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        ensureLocalIdentitiesIsMutable();
+        localIdentities_.set(index, value);
+        onChanged();
+      } else {
+        localIdentitiesBuilder_.setMessage(index, value);
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) A list of local identities supported by the server, if
+     * specified. Otherwise, the handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+     */
+    public Builder setLocalIdentities(
+        int index, io.grpc.alts.internal.Identity.Builder builderForValue) {
+      if (localIdentitiesBuilder_ == null) {
+        ensureLocalIdentitiesIsMutable();
+        localIdentities_.set(index, builderForValue.build());
+        onChanged();
+      } else {
+        localIdentitiesBuilder_.setMessage(index, builderForValue.build());
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) A list of local identities supported by the server, if
+     * specified. Otherwise, the handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+     */
+    public Builder addLocalIdentities(io.grpc.alts.internal.Identity value) {
+      if (localIdentitiesBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        ensureLocalIdentitiesIsMutable();
+        localIdentities_.add(value);
+        onChanged();
+      } else {
+        localIdentitiesBuilder_.addMessage(value);
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) A list of local identities supported by the server, if
+     * specified. Otherwise, the handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+     */
+    public Builder addLocalIdentities(
+        int index, io.grpc.alts.internal.Identity value) {
+      if (localIdentitiesBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        ensureLocalIdentitiesIsMutable();
+        localIdentities_.add(index, value);
+        onChanged();
+      } else {
+        localIdentitiesBuilder_.addMessage(index, value);
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) A list of local identities supported by the server, if
+     * specified. Otherwise, the handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+     */
+    public Builder addLocalIdentities(
+        io.grpc.alts.internal.Identity.Builder builderForValue) {
+      if (localIdentitiesBuilder_ == null) {
+        ensureLocalIdentitiesIsMutable();
+        localIdentities_.add(builderForValue.build());
+        onChanged();
+      } else {
+        localIdentitiesBuilder_.addMessage(builderForValue.build());
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) A list of local identities supported by the server, if
+     * specified. Otherwise, the handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+     */
+    public Builder addLocalIdentities(
+        int index, io.grpc.alts.internal.Identity.Builder builderForValue) {
+      if (localIdentitiesBuilder_ == null) {
+        ensureLocalIdentitiesIsMutable();
+        localIdentities_.add(index, builderForValue.build());
+        onChanged();
+      } else {
+        localIdentitiesBuilder_.addMessage(index, builderForValue.build());
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) A list of local identities supported by the server, if
+     * specified. Otherwise, the handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+     */
+    public Builder addAllLocalIdentities(
+        java.lang.Iterable<? extends io.grpc.alts.internal.Identity> values) {
+      if (localIdentitiesBuilder_ == null) {
+        ensureLocalIdentitiesIsMutable();
+        com.google.protobuf.AbstractMessageLite.Builder.addAll(
+            values, localIdentities_);
+        onChanged();
+      } else {
+        localIdentitiesBuilder_.addAllMessages(values);
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) A list of local identities supported by the server, if
+     * specified. Otherwise, the handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+     */
+    public Builder clearLocalIdentities() {
+      if (localIdentitiesBuilder_ == null) {
+        localIdentities_ = java.util.Collections.emptyList();
+        bitField0_ = (bitField0_ & ~0x00000002);
+        onChanged();
+      } else {
+        localIdentitiesBuilder_.clear();
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) A list of local identities supported by the server, if
+     * specified. Otherwise, the handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+     */
+    public Builder removeLocalIdentities(int index) {
+      if (localIdentitiesBuilder_ == null) {
+        ensureLocalIdentitiesIsMutable();
+        localIdentities_.remove(index);
+        onChanged();
+      } else {
+        localIdentitiesBuilder_.remove(index);
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) A list of local identities supported by the server, if
+     * specified. Otherwise, the handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+     */
+    public io.grpc.alts.internal.Identity.Builder getLocalIdentitiesBuilder(
+        int index) {
+      return getLocalIdentitiesFieldBuilder().getBuilder(index);
+    }
+    /**
+     * <pre>
+     * (Optional) A list of local identities supported by the server, if
+     * specified. Otherwise, the handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+     */
+    public io.grpc.alts.internal.IdentityOrBuilder getLocalIdentitiesOrBuilder(
+        int index) {
+      if (localIdentitiesBuilder_ == null) {
+        return localIdentities_.get(index);  } else {
+        return localIdentitiesBuilder_.getMessageOrBuilder(index);
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) A list of local identities supported by the server, if
+     * specified. Otherwise, the handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+     */
+    public java.util.List<? extends io.grpc.alts.internal.IdentityOrBuilder> 
+         getLocalIdentitiesOrBuilderList() {
+      if (localIdentitiesBuilder_ != null) {
+        return localIdentitiesBuilder_.getMessageOrBuilderList();
+      } else {
+        return java.util.Collections.unmodifiableList(localIdentities_);
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) A list of local identities supported by the server, if
+     * specified. Otherwise, the handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+     */
+    public io.grpc.alts.internal.Identity.Builder addLocalIdentitiesBuilder() {
+      return getLocalIdentitiesFieldBuilder().addBuilder(
+          io.grpc.alts.internal.Identity.getDefaultInstance());
+    }
+    /**
+     * <pre>
+     * (Optional) A list of local identities supported by the server, if
+     * specified. Otherwise, the handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+     */
+    public io.grpc.alts.internal.Identity.Builder addLocalIdentitiesBuilder(
+        int index) {
+      return getLocalIdentitiesFieldBuilder().addBuilder(
+          index, io.grpc.alts.internal.Identity.getDefaultInstance());
+    }
+    /**
+     * <pre>
+     * (Optional) A list of local identities supported by the server, if
+     * specified. Otherwise, the handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+     */
+    public java.util.List<io.grpc.alts.internal.Identity.Builder> 
+         getLocalIdentitiesBuilderList() {
+      return getLocalIdentitiesFieldBuilder().getBuilderList();
+    }
+    private com.google.protobuf.RepeatedFieldBuilderV3<
+        io.grpc.alts.internal.Identity, io.grpc.alts.internal.Identity.Builder, io.grpc.alts.internal.IdentityOrBuilder> 
+        getLocalIdentitiesFieldBuilder() {
+      if (localIdentitiesBuilder_ == null) {
+        localIdentitiesBuilder_ = new com.google.protobuf.RepeatedFieldBuilderV3<
+            io.grpc.alts.internal.Identity, io.grpc.alts.internal.Identity.Builder, io.grpc.alts.internal.IdentityOrBuilder>(
+                localIdentities_,
+                ((bitField0_ & 0x00000002) == 0x00000002),
+                getParentForChildren(),
+                isClean());
+        localIdentities_ = null;
+      }
+      return localIdentitiesBuilder_;
+    }
+    public final Builder setUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.setUnknownFieldsProto3(unknownFields);
+    }
+
+    public final Builder mergeUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.mergeUnknownFields(unknownFields);
+    }
+
+
+    // @@protoc_insertion_point(builder_scope:grpc.gcp.ServerHandshakeParameters)
+  }
+
+  // @@protoc_insertion_point(class_scope:grpc.gcp.ServerHandshakeParameters)
+  private static final io.grpc.alts.internal.ServerHandshakeParameters DEFAULT_INSTANCE;
+  static {
+    DEFAULT_INSTANCE = new io.grpc.alts.internal.ServerHandshakeParameters();
+  }
+
+  public static io.grpc.alts.internal.ServerHandshakeParameters getDefaultInstance() {
+    return DEFAULT_INSTANCE;
+  }
+
+  private static final com.google.protobuf.Parser<ServerHandshakeParameters>
+      PARSER = new com.google.protobuf.AbstractParser<ServerHandshakeParameters>() {
+    public ServerHandshakeParameters parsePartialFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return new ServerHandshakeParameters(input, extensionRegistry);
+    }
+  };
+
+  public static com.google.protobuf.Parser<ServerHandshakeParameters> parser() {
+    return PARSER;
+  }
+
+  @java.lang.Override
+  public com.google.protobuf.Parser<ServerHandshakeParameters> getParserForType() {
+    return PARSER;
+  }
+
+  public io.grpc.alts.internal.ServerHandshakeParameters getDefaultInstanceForType() {
+    return DEFAULT_INSTANCE;
+  }
+
+}
+
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/ServerHandshakeParametersOrBuilder.java b/alts/src/generated/main/java/io/grpc/alts/internal/ServerHandshakeParametersOrBuilder.java
new file mode 100644
index 0000000000..2b16fe509c
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/ServerHandshakeParametersOrBuilder.java
@@ -0,0 +1,97 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+public interface ServerHandshakeParametersOrBuilder extends
+    // @@protoc_insertion_point(interface_extends:grpc.gcp.ServerHandshakeParameters)
+    com.google.protobuf.MessageOrBuilder {
+
+  /**
+   * <pre>
+   * The record protocols supported by the server, e.g.,
+   * "ALTSRP_GCM_AES128".
+   * </pre>
+   *
+   * <code>repeated string record_protocols = 1;</code>
+   */
+  java.util.List<java.lang.String>
+      getRecordProtocolsList();
+  /**
+   * <pre>
+   * The record protocols supported by the server, e.g.,
+   * "ALTSRP_GCM_AES128".
+   * </pre>
+   *
+   * <code>repeated string record_protocols = 1;</code>
+   */
+  int getRecordProtocolsCount();
+  /**
+   * <pre>
+   * The record protocols supported by the server, e.g.,
+   * "ALTSRP_GCM_AES128".
+   * </pre>
+   *
+   * <code>repeated string record_protocols = 1;</code>
+   */
+  java.lang.String getRecordProtocols(int index);
+  /**
+   * <pre>
+   * The record protocols supported by the server, e.g.,
+   * "ALTSRP_GCM_AES128".
+   * </pre>
+   *
+   * <code>repeated string record_protocols = 1;</code>
+   */
+  com.google.protobuf.ByteString
+      getRecordProtocolsBytes(int index);
+
+  /**
+   * <pre>
+   * (Optional) A list of local identities supported by the server, if
+   * specified. Otherwise, the handshaker chooses a default local identity.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+   */
+  java.util.List<io.grpc.alts.internal.Identity> 
+      getLocalIdentitiesList();
+  /**
+   * <pre>
+   * (Optional) A list of local identities supported by the server, if
+   * specified. Otherwise, the handshaker chooses a default local identity.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+   */
+  io.grpc.alts.internal.Identity getLocalIdentities(int index);
+  /**
+   * <pre>
+   * (Optional) A list of local identities supported by the server, if
+   * specified. Otherwise, the handshaker chooses a default local identity.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+   */
+  int getLocalIdentitiesCount();
+  /**
+   * <pre>
+   * (Optional) A list of local identities supported by the server, if
+   * specified. Otherwise, the handshaker chooses a default local identity.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+   */
+  java.util.List<? extends io.grpc.alts.internal.IdentityOrBuilder> 
+      getLocalIdentitiesOrBuilderList();
+  /**
+   * <pre>
+   * (Optional) A list of local identities supported by the server, if
+   * specified. Otherwise, the handshaker chooses a default local identity.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity local_identities = 2;</code>
+   */
+  io.grpc.alts.internal.IdentityOrBuilder getLocalIdentitiesOrBuilder(
+      int index);
+}
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/StartClientHandshakeReq.java b/alts/src/generated/main/java/io/grpc/alts/internal/StartClientHandshakeReq.java
new file mode 100644
index 0000000000..41aeb12f8f
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/StartClientHandshakeReq.java
@@ -0,0 +1,2577 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+/**
+ * Protobuf type {@code grpc.gcp.StartClientHandshakeReq}
+ */
+public  final class StartClientHandshakeReq extends
+    com.google.protobuf.GeneratedMessageV3 implements
+    // @@protoc_insertion_point(message_implements:grpc.gcp.StartClientHandshakeReq)
+    StartClientHandshakeReqOrBuilder {
+private static final long serialVersionUID = 0L;
+  // Use StartClientHandshakeReq.newBuilder() to construct.
+  private StartClientHandshakeReq(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
+    super(builder);
+  }
+  private StartClientHandshakeReq() {
+    handshakeSecurityProtocol_ = 0;
+    applicationProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
+    recordProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
+    targetIdentities_ = java.util.Collections.emptyList();
+    targetName_ = "";
+  }
+
+  @java.lang.Override
+  public final com.google.protobuf.UnknownFieldSet
+  getUnknownFields() {
+    return this.unknownFields;
+  }
+  private StartClientHandshakeReq(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    this();
+    if (extensionRegistry == null) {
+      throw new java.lang.NullPointerException();
+    }
+    int mutable_bitField0_ = 0;
+    com.google.protobuf.UnknownFieldSet.Builder unknownFields =
+        com.google.protobuf.UnknownFieldSet.newBuilder();
+    try {
+      boolean done = false;
+      while (!done) {
+        int tag = input.readTag();
+        switch (tag) {
+          case 0:
+            done = true;
+            break;
+          default: {
+            if (!parseUnknownFieldProto3(
+                input, unknownFields, extensionRegistry, tag)) {
+              done = true;
+            }
+            break;
+          }
+          case 8: {
+            int rawValue = input.readEnum();
+
+            handshakeSecurityProtocol_ = rawValue;
+            break;
+          }
+          case 18: {
+            java.lang.String s = input.readStringRequireUtf8();
+            if (!((mutable_bitField0_ & 0x00000002) == 0x00000002)) {
+              applicationProtocols_ = new com.google.protobuf.LazyStringArrayList();
+              mutable_bitField0_ |= 0x00000002;
+            }
+            applicationProtocols_.add(s);
+            break;
+          }
+          case 26: {
+            java.lang.String s = input.readStringRequireUtf8();
+            if (!((mutable_bitField0_ & 0x00000004) == 0x00000004)) {
+              recordProtocols_ = new com.google.protobuf.LazyStringArrayList();
+              mutable_bitField0_ |= 0x00000004;
+            }
+            recordProtocols_.add(s);
+            break;
+          }
+          case 34: {
+            if (!((mutable_bitField0_ & 0x00000008) == 0x00000008)) {
+              targetIdentities_ = new java.util.ArrayList<io.grpc.alts.internal.Identity>();
+              mutable_bitField0_ |= 0x00000008;
+            }
+            targetIdentities_.add(
+                input.readMessage(io.grpc.alts.internal.Identity.parser(), extensionRegistry));
+            break;
+          }
+          case 42: {
+            io.grpc.alts.internal.Identity.Builder subBuilder = null;
+            if (localIdentity_ != null) {
+              subBuilder = localIdentity_.toBuilder();
+            }
+            localIdentity_ = input.readMessage(io.grpc.alts.internal.Identity.parser(), extensionRegistry);
+            if (subBuilder != null) {
+              subBuilder.mergeFrom(localIdentity_);
+              localIdentity_ = subBuilder.buildPartial();
+            }
+
+            break;
+          }
+          case 50: {
+            io.grpc.alts.internal.Endpoint.Builder subBuilder = null;
+            if (localEndpoint_ != null) {
+              subBuilder = localEndpoint_.toBuilder();
+            }
+            localEndpoint_ = input.readMessage(io.grpc.alts.internal.Endpoint.parser(), extensionRegistry);
+            if (subBuilder != null) {
+              subBuilder.mergeFrom(localEndpoint_);
+              localEndpoint_ = subBuilder.buildPartial();
+            }
+
+            break;
+          }
+          case 58: {
+            io.grpc.alts.internal.Endpoint.Builder subBuilder = null;
+            if (remoteEndpoint_ != null) {
+              subBuilder = remoteEndpoint_.toBuilder();
+            }
+            remoteEndpoint_ = input.readMessage(io.grpc.alts.internal.Endpoint.parser(), extensionRegistry);
+            if (subBuilder != null) {
+              subBuilder.mergeFrom(remoteEndpoint_);
+              remoteEndpoint_ = subBuilder.buildPartial();
+            }
+
+            break;
+          }
+          case 66: {
+            java.lang.String s = input.readStringRequireUtf8();
+
+            targetName_ = s;
+            break;
+          }
+          case 74: {
+            io.grpc.alts.internal.RpcProtocolVersions.Builder subBuilder = null;
+            if (rpcVersions_ != null) {
+              subBuilder = rpcVersions_.toBuilder();
+            }
+            rpcVersions_ = input.readMessage(io.grpc.alts.internal.RpcProtocolVersions.parser(), extensionRegistry);
+            if (subBuilder != null) {
+              subBuilder.mergeFrom(rpcVersions_);
+              rpcVersions_ = subBuilder.buildPartial();
+            }
+
+            break;
+          }
+        }
+      }
+    } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+      throw e.setUnfinishedMessage(this);
+    } catch (java.io.IOException e) {
+      throw new com.google.protobuf.InvalidProtocolBufferException(
+          e).setUnfinishedMessage(this);
+    } finally {
+      if (((mutable_bitField0_ & 0x00000002) == 0x00000002)) {
+        applicationProtocols_ = applicationProtocols_.getUnmodifiableView();
+      }
+      if (((mutable_bitField0_ & 0x00000004) == 0x00000004)) {
+        recordProtocols_ = recordProtocols_.getUnmodifiableView();
+      }
+      if (((mutable_bitField0_ & 0x00000008) == 0x00000008)) {
+        targetIdentities_ = java.util.Collections.unmodifiableList(targetIdentities_);
+      }
+      this.unknownFields = unknownFields.build();
+      makeExtensionsImmutable();
+    }
+  }
+  public static final com.google.protobuf.Descriptors.Descriptor
+      getDescriptor() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_StartClientHandshakeReq_descriptor;
+  }
+
+  protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internalGetFieldAccessorTable() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_StartClientHandshakeReq_fieldAccessorTable
+        .ensureFieldAccessorsInitialized(
+            io.grpc.alts.internal.StartClientHandshakeReq.class, io.grpc.alts.internal.StartClientHandshakeReq.Builder.class);
+  }
+
+  private int bitField0_;
+  public static final int HANDSHAKE_SECURITY_PROTOCOL_FIELD_NUMBER = 1;
+  private int handshakeSecurityProtocol_;
+  /**
+   * <pre>
+   * Handshake security protocol requested by the client.
+   * </pre>
+   *
+   * <code>.grpc.gcp.HandshakeProtocol handshake_security_protocol = 1;</code>
+   */
+  public int getHandshakeSecurityProtocolValue() {
+    return handshakeSecurityProtocol_;
+  }
+  /**
+   * <pre>
+   * Handshake security protocol requested by the client.
+   * </pre>
+   *
+   * <code>.grpc.gcp.HandshakeProtocol handshake_security_protocol = 1;</code>
+   */
+  public io.grpc.alts.internal.HandshakeProtocol getHandshakeSecurityProtocol() {
+    io.grpc.alts.internal.HandshakeProtocol result = io.grpc.alts.internal.HandshakeProtocol.valueOf(handshakeSecurityProtocol_);
+    return result == null ? io.grpc.alts.internal.HandshakeProtocol.UNRECOGNIZED : result;
+  }
+
+  public static final int APPLICATION_PROTOCOLS_FIELD_NUMBER = 2;
+  private com.google.protobuf.LazyStringList applicationProtocols_;
+  /**
+   * <pre>
+   * The application protocols supported by the client, e.g., "h2" (for http2),
+   * "grpc".
+   * </pre>
+   *
+   * <code>repeated string application_protocols = 2;</code>
+   */
+  public com.google.protobuf.ProtocolStringList
+      getApplicationProtocolsList() {
+    return applicationProtocols_;
+  }
+  /**
+   * <pre>
+   * The application protocols supported by the client, e.g., "h2" (for http2),
+   * "grpc".
+   * </pre>
+   *
+   * <code>repeated string application_protocols = 2;</code>
+   */
+  public int getApplicationProtocolsCount() {
+    return applicationProtocols_.size();
+  }
+  /**
+   * <pre>
+   * The application protocols supported by the client, e.g., "h2" (for http2),
+   * "grpc".
+   * </pre>
+   *
+   * <code>repeated string application_protocols = 2;</code>
+   */
+  public java.lang.String getApplicationProtocols(int index) {
+    return applicationProtocols_.get(index);
+  }
+  /**
+   * <pre>
+   * The application protocols supported by the client, e.g., "h2" (for http2),
+   * "grpc".
+   * </pre>
+   *
+   * <code>repeated string application_protocols = 2;</code>
+   */
+  public com.google.protobuf.ByteString
+      getApplicationProtocolsBytes(int index) {
+    return applicationProtocols_.getByteString(index);
+  }
+
+  public static final int RECORD_PROTOCOLS_FIELD_NUMBER = 3;
+  private com.google.protobuf.LazyStringList recordProtocols_;
+  /**
+   * <pre>
+   * The record protocols supported by the client, e.g.,
+   * "ALTSRP_GCM_AES128".
+   * </pre>
+   *
+   * <code>repeated string record_protocols = 3;</code>
+   */
+  public com.google.protobuf.ProtocolStringList
+      getRecordProtocolsList() {
+    return recordProtocols_;
+  }
+  /**
+   * <pre>
+   * The record protocols supported by the client, e.g.,
+   * "ALTSRP_GCM_AES128".
+   * </pre>
+   *
+   * <code>repeated string record_protocols = 3;</code>
+   */
+  public int getRecordProtocolsCount() {
+    return recordProtocols_.size();
+  }
+  /**
+   * <pre>
+   * The record protocols supported by the client, e.g.,
+   * "ALTSRP_GCM_AES128".
+   * </pre>
+   *
+   * <code>repeated string record_protocols = 3;</code>
+   */
+  public java.lang.String getRecordProtocols(int index) {
+    return recordProtocols_.get(index);
+  }
+  /**
+   * <pre>
+   * The record protocols supported by the client, e.g.,
+   * "ALTSRP_GCM_AES128".
+   * </pre>
+   *
+   * <code>repeated string record_protocols = 3;</code>
+   */
+  public com.google.protobuf.ByteString
+      getRecordProtocolsBytes(int index) {
+    return recordProtocols_.getByteString(index);
+  }
+
+  public static final int TARGET_IDENTITIES_FIELD_NUMBER = 4;
+  private java.util.List<io.grpc.alts.internal.Identity> targetIdentities_;
+  /**
+   * <pre>
+   * (Optional) Describes which server identities are acceptable by the client.
+   * If target identities are provided and none of them matches the peer
+   * identity of the server, handshake will fail.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+   */
+  public java.util.List<io.grpc.alts.internal.Identity> getTargetIdentitiesList() {
+    return targetIdentities_;
+  }
+  /**
+   * <pre>
+   * (Optional) Describes which server identities are acceptable by the client.
+   * If target identities are provided and none of them matches the peer
+   * identity of the server, handshake will fail.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+   */
+  public java.util.List<? extends io.grpc.alts.internal.IdentityOrBuilder> 
+      getTargetIdentitiesOrBuilderList() {
+    return targetIdentities_;
+  }
+  /**
+   * <pre>
+   * (Optional) Describes which server identities are acceptable by the client.
+   * If target identities are provided and none of them matches the peer
+   * identity of the server, handshake will fail.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+   */
+  public int getTargetIdentitiesCount() {
+    return targetIdentities_.size();
+  }
+  /**
+   * <pre>
+   * (Optional) Describes which server identities are acceptable by the client.
+   * If target identities are provided and none of them matches the peer
+   * identity of the server, handshake will fail.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+   */
+  public io.grpc.alts.internal.Identity getTargetIdentities(int index) {
+    return targetIdentities_.get(index);
+  }
+  /**
+   * <pre>
+   * (Optional) Describes which server identities are acceptable by the client.
+   * If target identities are provided and none of them matches the peer
+   * identity of the server, handshake will fail.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+   */
+  public io.grpc.alts.internal.IdentityOrBuilder getTargetIdentitiesOrBuilder(
+      int index) {
+    return targetIdentities_.get(index);
+  }
+
+  public static final int LOCAL_IDENTITY_FIELD_NUMBER = 5;
+  private io.grpc.alts.internal.Identity localIdentity_;
+  /**
+   * <pre>
+   * (Optional) Application may specify a local identity. Otherwise, the
+   * handshaker chooses a default local identity.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Identity local_identity = 5;</code>
+   */
+  public boolean hasLocalIdentity() {
+    return localIdentity_ != null;
+  }
+  /**
+   * <pre>
+   * (Optional) Application may specify a local identity. Otherwise, the
+   * handshaker chooses a default local identity.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Identity local_identity = 5;</code>
+   */
+  public io.grpc.alts.internal.Identity getLocalIdentity() {
+    return localIdentity_ == null ? io.grpc.alts.internal.Identity.getDefaultInstance() : localIdentity_;
+  }
+  /**
+   * <pre>
+   * (Optional) Application may specify a local identity. Otherwise, the
+   * handshaker chooses a default local identity.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Identity local_identity = 5;</code>
+   */
+  public io.grpc.alts.internal.IdentityOrBuilder getLocalIdentityOrBuilder() {
+    return getLocalIdentity();
+  }
+
+  public static final int LOCAL_ENDPOINT_FIELD_NUMBER = 6;
+  private io.grpc.alts.internal.Endpoint localEndpoint_;
+  /**
+   * <pre>
+   * (Optional) Local endpoint information of the connection to the server,
+   * such as local IP address, port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
+   */
+  public boolean hasLocalEndpoint() {
+    return localEndpoint_ != null;
+  }
+  /**
+   * <pre>
+   * (Optional) Local endpoint information of the connection to the server,
+   * such as local IP address, port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
+   */
+  public io.grpc.alts.internal.Endpoint getLocalEndpoint() {
+    return localEndpoint_ == null ? io.grpc.alts.internal.Endpoint.getDefaultInstance() : localEndpoint_;
+  }
+  /**
+   * <pre>
+   * (Optional) Local endpoint information of the connection to the server,
+   * such as local IP address, port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
+   */
+  public io.grpc.alts.internal.EndpointOrBuilder getLocalEndpointOrBuilder() {
+    return getLocalEndpoint();
+  }
+
+  public static final int REMOTE_ENDPOINT_FIELD_NUMBER = 7;
+  private io.grpc.alts.internal.Endpoint remoteEndpoint_;
+  /**
+   * <pre>
+   * (Optional) Endpoint information of the remote server, such as IP address,
+   * port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
+   */
+  public boolean hasRemoteEndpoint() {
+    return remoteEndpoint_ != null;
+  }
+  /**
+   * <pre>
+   * (Optional) Endpoint information of the remote server, such as IP address,
+   * port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
+   */
+  public io.grpc.alts.internal.Endpoint getRemoteEndpoint() {
+    return remoteEndpoint_ == null ? io.grpc.alts.internal.Endpoint.getDefaultInstance() : remoteEndpoint_;
+  }
+  /**
+   * <pre>
+   * (Optional) Endpoint information of the remote server, such as IP address,
+   * port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
+   */
+  public io.grpc.alts.internal.EndpointOrBuilder getRemoteEndpointOrBuilder() {
+    return getRemoteEndpoint();
+  }
+
+  public static final int TARGET_NAME_FIELD_NUMBER = 8;
+  private volatile java.lang.Object targetName_;
+  /**
+   * <pre>
+   * (Optional) If target name is provided, a secure naming check is performed
+   * to verify that the peer authenticated identity is indeed authorized to run
+   * the target name.
+   * </pre>
+   *
+   * <code>string target_name = 8;</code>
+   */
+  public java.lang.String getTargetName() {
+    java.lang.Object ref = targetName_;
+    if (ref instanceof java.lang.String) {
+      return (java.lang.String) ref;
+    } else {
+      com.google.protobuf.ByteString bs = 
+          (com.google.protobuf.ByteString) ref;
+      java.lang.String s = bs.toStringUtf8();
+      targetName_ = s;
+      return s;
+    }
+  }
+  /**
+   * <pre>
+   * (Optional) If target name is provided, a secure naming check is performed
+   * to verify that the peer authenticated identity is indeed authorized to run
+   * the target name.
+   * </pre>
+   *
+   * <code>string target_name = 8;</code>
+   */
+  public com.google.protobuf.ByteString
+      getTargetNameBytes() {
+    java.lang.Object ref = targetName_;
+    if (ref instanceof java.lang.String) {
+      com.google.protobuf.ByteString b = 
+          com.google.protobuf.ByteString.copyFromUtf8(
+              (java.lang.String) ref);
+      targetName_ = b;
+      return b;
+    } else {
+      return (com.google.protobuf.ByteString) ref;
+    }
+  }
+
+  public static final int RPC_VERSIONS_FIELD_NUMBER = 9;
+  private io.grpc.alts.internal.RpcProtocolVersions rpcVersions_;
+  /**
+   * <pre>
+   * (Optional) RPC protocol versions supported by the client.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
+   */
+  public boolean hasRpcVersions() {
+    return rpcVersions_ != null;
+  }
+  /**
+   * <pre>
+   * (Optional) RPC protocol versions supported by the client.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
+   */
+  public io.grpc.alts.internal.RpcProtocolVersions getRpcVersions() {
+    return rpcVersions_ == null ? io.grpc.alts.internal.RpcProtocolVersions.getDefaultInstance() : rpcVersions_;
+  }
+  /**
+   * <pre>
+   * (Optional) RPC protocol versions supported by the client.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
+   */
+  public io.grpc.alts.internal.RpcProtocolVersionsOrBuilder getRpcVersionsOrBuilder() {
+    return getRpcVersions();
+  }
+
+  private byte memoizedIsInitialized = -1;
+  public final boolean isInitialized() {
+    byte isInitialized = memoizedIsInitialized;
+    if (isInitialized == 1) return true;
+    if (isInitialized == 0) return false;
+
+    memoizedIsInitialized = 1;
+    return true;
+  }
+
+  public void writeTo(com.google.protobuf.CodedOutputStream output)
+                      throws java.io.IOException {
+    if (handshakeSecurityProtocol_ != io.grpc.alts.internal.HandshakeProtocol.HANDSHAKE_PROTOCOL_UNSPECIFIED.getNumber()) {
+      output.writeEnum(1, handshakeSecurityProtocol_);
+    }
+    for (int i = 0; i < applicationProtocols_.size(); i++) {
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+    if (rpcVersions_ != null) {
+      output.writeMessage(9, getRpcVersions());
+    }
+    unknownFields.writeTo(output);
+  }
+
+  public int getSerializedSize() {
+    int size = memoizedSize;
+    if (size != -1) return size;
+
+    size = 0;
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+        .computeEnumSize(1, handshakeSecurityProtocol_);
+    }
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+      size += dataSize;
+      size += 1 * getApplicationProtocolsList().size();
+    }
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+        .computeMessageSize(5, getLocalIdentity());
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+        .computeMessageSize(6, getLocalEndpoint());
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+        .computeMessageSize(7, getRemoteEndpoint());
+    }
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+    }
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+        .computeMessageSize(9, getRpcVersions());
+    }
+    size += unknownFields.getSerializedSize();
+    memoizedSize = size;
+    return size;
+  }
+
+  @java.lang.Override
+  public boolean equals(final java.lang.Object obj) {
+    if (obj == this) {
+     return true;
+    }
+    if (!(obj instanceof io.grpc.alts.internal.StartClientHandshakeReq)) {
+      return super.equals(obj);
+    }
+    io.grpc.alts.internal.StartClientHandshakeReq other = (io.grpc.alts.internal.StartClientHandshakeReq) obj;
+
+    boolean result = true;
+    result = result && handshakeSecurityProtocol_ == other.handshakeSecurityProtocol_;
+    result = result && getApplicationProtocolsList()
+        .equals(other.getApplicationProtocolsList());
+    result = result && getRecordProtocolsList()
+        .equals(other.getRecordProtocolsList());
+    result = result && getTargetIdentitiesList()
+        .equals(other.getTargetIdentitiesList());
+    result = result && (hasLocalIdentity() == other.hasLocalIdentity());
+    if (hasLocalIdentity()) {
+      result = result && getLocalIdentity()
+          .equals(other.getLocalIdentity());
+    }
+    result = result && (hasLocalEndpoint() == other.hasLocalEndpoint());
+    if (hasLocalEndpoint()) {
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+          .equals(other.getLocalEndpoint());
+    }
+    result = result && (hasRemoteEndpoint() == other.hasRemoteEndpoint());
+    if (hasRemoteEndpoint()) {
+      result = result && getRemoteEndpoint()
+          .equals(other.getRemoteEndpoint());
+    }
+    result = result && getTargetName()
+        .equals(other.getTargetName());
+    result = result && (hasRpcVersions() == other.hasRpcVersions());
+    if (hasRpcVersions()) {
+      result = result && getRpcVersions()
+          .equals(other.getRpcVersions());
+    }
+    result = result && unknownFields.equals(other.unknownFields);
+    return result;
+  }
+
+  @java.lang.Override
+  public int hashCode() {
+    if (memoizedHashCode != 0) {
+      return memoizedHashCode;
+    }
+    int hash = 41;
+    hash = (19 * hash) + getDescriptor().hashCode();
+    hash = (37 * hash) + HANDSHAKE_SECURITY_PROTOCOL_FIELD_NUMBER;
+    hash = (53 * hash) + handshakeSecurityProtocol_;
+    if (getApplicationProtocolsCount() > 0) {
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+      hash = (53 * hash) + getApplicationProtocolsList().hashCode();
+    }
+    if (getRecordProtocolsCount() > 0) {
+      hash = (37 * hash) + RECORD_PROTOCOLS_FIELD_NUMBER;
+      hash = (53 * hash) + getRecordProtocolsList().hashCode();
+    }
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+      hash = (53 * hash) + getLocalIdentity().hashCode();
+    }
+    if (hasLocalEndpoint()) {
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+      hash = (53 * hash) + getLocalEndpoint().hashCode();
+    }
+    if (hasRemoteEndpoint()) {
+      hash = (37 * hash) + REMOTE_ENDPOINT_FIELD_NUMBER;
+      hash = (53 * hash) + getRemoteEndpoint().hashCode();
+    }
+    hash = (37 * hash) + TARGET_NAME_FIELD_NUMBER;
+    hash = (53 * hash) + getTargetName().hashCode();
+    if (hasRpcVersions()) {
+      hash = (37 * hash) + RPC_VERSIONS_FIELD_NUMBER;
+      hash = (53 * hash) + getRpcVersions().hashCode();
+    }
+    hash = (29 * hash) + unknownFields.hashCode();
+    memoizedHashCode = hash;
+    return hash;
+  }
+
+  public static io.grpc.alts.internal.StartClientHandshakeReq parseFrom(
+      java.nio.ByteBuffer data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.StartClientHandshakeReq parseFrom(
+      java.nio.ByteBuffer data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.StartClientHandshakeReq parseFrom(
+      com.google.protobuf.ByteString data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.StartClientHandshakeReq parseFrom(
+      com.google.protobuf.ByteString data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.StartClientHandshakeReq parseFrom(byte[] data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.StartClientHandshakeReq parseFrom(
+      byte[] data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.StartClientHandshakeReq parseFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.StartClientHandshakeReq parseFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.StartClientHandshakeReq parseDelimitedFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.StartClientHandshakeReq parseDelimitedFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.StartClientHandshakeReq parseFrom(
+      com.google.protobuf.CodedInputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.StartClientHandshakeReq parseFrom(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+
+  public Builder newBuilderForType() { return newBuilder(); }
+  public static Builder newBuilder() {
+    return DEFAULT_INSTANCE.toBuilder();
+  }
+  public static Builder newBuilder(io.grpc.alts.internal.StartClientHandshakeReq prototype) {
+    return DEFAULT_INSTANCE.toBuilder().mergeFrom(prototype);
+  }
+  public Builder toBuilder() {
+    return this == DEFAULT_INSTANCE
+        ? new Builder() : new Builder().mergeFrom(this);
+  }
+
+  @java.lang.Override
+  protected Builder newBuilderForType(
+      com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+    Builder builder = new Builder(parent);
+    return builder;
+  }
+  /**
+   * Protobuf type {@code grpc.gcp.StartClientHandshakeReq}
+   */
+  public static final class Builder extends
+      com.google.protobuf.GeneratedMessageV3.Builder<Builder> implements
+      // @@protoc_insertion_point(builder_implements:grpc.gcp.StartClientHandshakeReq)
+      io.grpc.alts.internal.StartClientHandshakeReqOrBuilder {
+    public static final com.google.protobuf.Descriptors.Descriptor
+        getDescriptor() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_StartClientHandshakeReq_descriptor;
+    }
+
+    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+        internalGetFieldAccessorTable() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_StartClientHandshakeReq_fieldAccessorTable
+          .ensureFieldAccessorsInitialized(
+              io.grpc.alts.internal.StartClientHandshakeReq.class, io.grpc.alts.internal.StartClientHandshakeReq.Builder.class);
+    }
+
+    // Construct using io.grpc.alts.internal.StartClientHandshakeReq.newBuilder()
+    private Builder() {
+      maybeForceBuilderInitialization();
+    }
+
+    private Builder(
+        com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+      super(parent);
+      maybeForceBuilderInitialization();
+    }
+    private void maybeForceBuilderInitialization() {
+      if (com.google.protobuf.GeneratedMessageV3
+              .alwaysUseFieldBuilders) {
+        getTargetIdentitiesFieldBuilder();
+      }
+    }
+    public Builder clear() {
+      super.clear();
+      handshakeSecurityProtocol_ = 0;
+
+      applicationProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
+      bitField0_ = (bitField0_ & ~0x00000002);
+      recordProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
+      bitField0_ = (bitField0_ & ~0x00000004);
+      if (targetIdentitiesBuilder_ == null) {
+        targetIdentities_ = java.util.Collections.emptyList();
+        bitField0_ = (bitField0_ & ~0x00000008);
+      } else {
+        targetIdentitiesBuilder_.clear();
+      }
+      if (localIdentityBuilder_ == null) {
+        localIdentity_ = null;
+      } else {
+        localIdentity_ = null;
+        localIdentityBuilder_ = null;
+      }
+      if (localEndpointBuilder_ == null) {
+        localEndpoint_ = null;
+      } else {
+        localEndpoint_ = null;
+        localEndpointBuilder_ = null;
+      }
+      if (remoteEndpointBuilder_ == null) {
+        remoteEndpoint_ = null;
+      } else {
+        remoteEndpoint_ = null;
+        remoteEndpointBuilder_ = null;
+      }
+      targetName_ = "";
+
+      if (rpcVersionsBuilder_ == null) {
+        rpcVersions_ = null;
+      } else {
+        rpcVersions_ = null;
+        rpcVersionsBuilder_ = null;
+      }
+      return this;
+    }
+
+    public com.google.protobuf.Descriptors.Descriptor
+        getDescriptorForType() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_StartClientHandshakeReq_descriptor;
+    }
+
+    public io.grpc.alts.internal.StartClientHandshakeReq getDefaultInstanceForType() {
+      return io.grpc.alts.internal.StartClientHandshakeReq.getDefaultInstance();
+    }
+
+    public io.grpc.alts.internal.StartClientHandshakeReq build() {
+      io.grpc.alts.internal.StartClientHandshakeReq result = buildPartial();
+      if (!result.isInitialized()) {
+        throw newUninitializedMessageException(result);
+      }
+      return result;
+    }
+
+    public io.grpc.alts.internal.StartClientHandshakeReq buildPartial() {
+      io.grpc.alts.internal.StartClientHandshakeReq result = new io.grpc.alts.internal.StartClientHandshakeReq(this);
+      int from_bitField0_ = bitField0_;
+      int to_bitField0_ = 0;
+      result.handshakeSecurityProtocol_ = handshakeSecurityProtocol_;
+      if (((bitField0_ & 0x00000002) == 0x00000002)) {
+        applicationProtocols_ = applicationProtocols_.getUnmodifiableView();
+        bitField0_ = (bitField0_ & ~0x00000002);
+      }
+      result.applicationProtocols_ = applicationProtocols_;
+      if (((bitField0_ & 0x00000004) == 0x00000004)) {
+        recordProtocols_ = recordProtocols_.getUnmodifiableView();
+        bitField0_ = (bitField0_ & ~0x00000004);
+      }
+      result.recordProtocols_ = recordProtocols_;
+      if (targetIdentitiesBuilder_ == null) {
+        if (((bitField0_ & 0x00000008) == 0x00000008)) {
+          targetIdentities_ = java.util.Collections.unmodifiableList(targetIdentities_);
+          bitField0_ = (bitField0_ & ~0x00000008);
+        }
+        result.targetIdentities_ = targetIdentities_;
+      } else {
+        result.targetIdentities_ = targetIdentitiesBuilder_.build();
+      }
+      if (localIdentityBuilder_ == null) {
+        result.localIdentity_ = localIdentity_;
+      } else {
+        result.localIdentity_ = localIdentityBuilder_.build();
+      }
+      if (localEndpointBuilder_ == null) {
+        result.localEndpoint_ = localEndpoint_;
+      } else {
+        result.localEndpoint_ = localEndpointBuilder_.build();
+      }
+      if (remoteEndpointBuilder_ == null) {
+        result.remoteEndpoint_ = remoteEndpoint_;
+      } else {
+        result.remoteEndpoint_ = remoteEndpointBuilder_.build();
+      }
+      result.targetName_ = targetName_;
+      if (rpcVersionsBuilder_ == null) {
+        result.rpcVersions_ = rpcVersions_;
+      } else {
+        result.rpcVersions_ = rpcVersionsBuilder_.build();
+      }
+      result.bitField0_ = to_bitField0_;
+      onBuilt();
+      return result;
+    }
+
+    public Builder clone() {
+      return (Builder) super.clone();
+    }
+    public Builder setField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.setField(field, value);
+    }
+    public Builder clearField(
+        com.google.protobuf.Descriptors.FieldDescriptor field) {
+      return (Builder) super.clearField(field);
+    }
+    public Builder clearOneof(
+        com.google.protobuf.Descriptors.OneofDescriptor oneof) {
+      return (Builder) super.clearOneof(oneof);
+    }
+    public Builder setRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        int index, java.lang.Object value) {
+      return (Builder) super.setRepeatedField(field, index, value);
+    }
+    public Builder addRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.addRepeatedField(field, value);
+    }
+    public Builder mergeFrom(com.google.protobuf.Message other) {
+      if (other instanceof io.grpc.alts.internal.StartClientHandshakeReq) {
+        return mergeFrom((io.grpc.alts.internal.StartClientHandshakeReq)other);
+      } else {
+        super.mergeFrom(other);
+        return this;
+      }
+    }
+
+    public Builder mergeFrom(io.grpc.alts.internal.StartClientHandshakeReq other) {
+      if (other == io.grpc.alts.internal.StartClientHandshakeReq.getDefaultInstance()) return this;
+      if (other.handshakeSecurityProtocol_ != 0) {
+        setHandshakeSecurityProtocolValue(other.getHandshakeSecurityProtocolValue());
+      }
+      if (!other.applicationProtocols_.isEmpty()) {
+        if (applicationProtocols_.isEmpty()) {
+          applicationProtocols_ = other.applicationProtocols_;
+          bitField0_ = (bitField0_ & ~0x00000002);
+        } else {
+          ensureApplicationProtocolsIsMutable();
+          applicationProtocols_.addAll(other.applicationProtocols_);
+        }
+        onChanged();
+      }
+      if (!other.recordProtocols_.isEmpty()) {
+        if (recordProtocols_.isEmpty()) {
+          recordProtocols_ = other.recordProtocols_;
+          bitField0_ = (bitField0_ & ~0x00000004);
+        } else {
+          ensureRecordProtocolsIsMutable();
+          recordProtocols_.addAll(other.recordProtocols_);
+        }
+        onChanged();
+      }
+      if (targetIdentitiesBuilder_ == null) {
+        if (!other.targetIdentities_.isEmpty()) {
+          if (targetIdentities_.isEmpty()) {
+            targetIdentities_ = other.targetIdentities_;
+            bitField0_ = (bitField0_ & ~0x00000008);
+          } else {
+            ensureTargetIdentitiesIsMutable();
+            targetIdentities_.addAll(other.targetIdentities_);
+          }
+          onChanged();
+        }
+      } else {
+        if (!other.targetIdentities_.isEmpty()) {
+          if (targetIdentitiesBuilder_.isEmpty()) {
+            targetIdentitiesBuilder_.dispose();
+            targetIdentitiesBuilder_ = null;
+            targetIdentities_ = other.targetIdentities_;
+            bitField0_ = (bitField0_ & ~0x00000008);
+            targetIdentitiesBuilder_ = 
+              com.google.protobuf.GeneratedMessageV3.alwaysUseFieldBuilders ?
+                 getTargetIdentitiesFieldBuilder() : null;
+          } else {
+            targetIdentitiesBuilder_.addAllMessages(other.targetIdentities_);
+          }
+        }
+      }
+      if (other.hasLocalIdentity()) {
+        mergeLocalIdentity(other.getLocalIdentity());
+      }
+      if (other.hasLocalEndpoint()) {
+        mergeLocalEndpoint(other.getLocalEndpoint());
+      }
+      if (other.hasRemoteEndpoint()) {
+        mergeRemoteEndpoint(other.getRemoteEndpoint());
+      }
+      if (!other.getTargetName().isEmpty()) {
+        targetName_ = other.targetName_;
+        onChanged();
+      }
+      if (other.hasRpcVersions()) {
+        mergeRpcVersions(other.getRpcVersions());
+      }
+      this.mergeUnknownFields(other.unknownFields);
+      onChanged();
+      return this;
+    }
+
+    public final boolean isInitialized() {
+      return true;
+    }
+
+    public Builder mergeFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      io.grpc.alts.internal.StartClientHandshakeReq parsedMessage = null;
+      try {
+        parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);
+      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+        parsedMessage = (io.grpc.alts.internal.StartClientHandshakeReq) e.getUnfinishedMessage();
+        throw e.unwrapIOException();
+      } finally {
+        if (parsedMessage != null) {
+          mergeFrom(parsedMessage);
+        }
+      }
+      return this;
+    }
+    private int bitField0_;
+
+    private int handshakeSecurityProtocol_ = 0;
+    /**
+     * <pre>
+     * Handshake security protocol requested by the client.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakeProtocol handshake_security_protocol = 1;</code>
+     */
+    public int getHandshakeSecurityProtocolValue() {
+      return handshakeSecurityProtocol_;
+    }
+    /**
+     * <pre>
+     * Handshake security protocol requested by the client.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakeProtocol handshake_security_protocol = 1;</code>
+     */
+    public Builder setHandshakeSecurityProtocolValue(int value) {
+      handshakeSecurityProtocol_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * Handshake security protocol requested by the client.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakeProtocol handshake_security_protocol = 1;</code>
+     */
+    public io.grpc.alts.internal.HandshakeProtocol getHandshakeSecurityProtocol() {
+      io.grpc.alts.internal.HandshakeProtocol result = io.grpc.alts.internal.HandshakeProtocol.valueOf(handshakeSecurityProtocol_);
+      return result == null ? io.grpc.alts.internal.HandshakeProtocol.UNRECOGNIZED : result;
+    }
+    /**
+     * <pre>
+     * Handshake security protocol requested by the client.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakeProtocol handshake_security_protocol = 1;</code>
+     */
+    public Builder setHandshakeSecurityProtocol(io.grpc.alts.internal.HandshakeProtocol value) {
+      if (value == null) {
+        throw new NullPointerException();
+      }
+      
+      handshakeSecurityProtocol_ = value.getNumber();
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * Handshake security protocol requested by the client.
+     * </pre>
+     *
+     * <code>.grpc.gcp.HandshakeProtocol handshake_security_protocol = 1;</code>
+     */
+    public Builder clearHandshakeSecurityProtocol() {
+      
+      handshakeSecurityProtocol_ = 0;
+      onChanged();
+      return this;
+    }
+
+    private com.google.protobuf.LazyStringList applicationProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
+    private void ensureApplicationProtocolsIsMutable() {
+      if (!((bitField0_ & 0x00000002) == 0x00000002)) {
+        applicationProtocols_ = new com.google.protobuf.LazyStringArrayList(applicationProtocols_);
+        bitField0_ |= 0x00000002;
+       }
+    }
+    /**
+     * <pre>
+     * The application protocols supported by the client, e.g., "h2" (for http2),
+     * "grpc".
+     * </pre>
+     *
+     * <code>repeated string application_protocols = 2;</code>
+     */
+    public com.google.protobuf.ProtocolStringList
+        getApplicationProtocolsList() {
+      return applicationProtocols_.getUnmodifiableView();
+    }
+    /**
+     * <pre>
+     * The application protocols supported by the client, e.g., "h2" (for http2),
+     * "grpc".
+     * </pre>
+     *
+     * <code>repeated string application_protocols = 2;</code>
+     */
+    public int getApplicationProtocolsCount() {
+      return applicationProtocols_.size();
+    }
+    /**
+     * <pre>
+     * The application protocols supported by the client, e.g., "h2" (for http2),
+     * "grpc".
+     * </pre>
+     *
+     * <code>repeated string application_protocols = 2;</code>
+     */
+    public java.lang.String getApplicationProtocols(int index) {
+      return applicationProtocols_.get(index);
+    }
+    /**
+     * <pre>
+     * The application protocols supported by the client, e.g., "h2" (for http2),
+     * "grpc".
+     * </pre>
+     *
+     * <code>repeated string application_protocols = 2;</code>
+     */
+    public com.google.protobuf.ByteString
+        getApplicationProtocolsBytes(int index) {
+      return applicationProtocols_.getByteString(index);
+    }
+    /**
+     * <pre>
+     * The application protocols supported by the client, e.g., "h2" (for http2),
+     * "grpc".
+     * </pre>
+     *
+     * <code>repeated string application_protocols = 2;</code>
+     */
+    public Builder setApplicationProtocols(
+        int index, java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  ensureApplicationProtocolsIsMutable();
+      applicationProtocols_.set(index, value);
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The application protocols supported by the client, e.g., "h2" (for http2),
+     * "grpc".
+     * </pre>
+     *
+     * <code>repeated string application_protocols = 2;</code>
+     */
+    public Builder addApplicationProtocols(
+        java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  ensureApplicationProtocolsIsMutable();
+      applicationProtocols_.add(value);
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The application protocols supported by the client, e.g., "h2" (for http2),
+     * "grpc".
+     * </pre>
+     *
+     * <code>repeated string application_protocols = 2;</code>
+     */
+    public Builder addAllApplicationProtocols(
+        java.lang.Iterable<java.lang.String> values) {
+      ensureApplicationProtocolsIsMutable();
+      com.google.protobuf.AbstractMessageLite.Builder.addAll(
+          values, applicationProtocols_);
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The application protocols supported by the client, e.g., "h2" (for http2),
+     * "grpc".
+     * </pre>
+     *
+     * <code>repeated string application_protocols = 2;</code>
+     */
+    public Builder clearApplicationProtocols() {
+      applicationProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
+      bitField0_ = (bitField0_ & ~0x00000002);
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The application protocols supported by the client, e.g., "h2" (for http2),
+     * "grpc".
+     * </pre>
+     *
+     * <code>repeated string application_protocols = 2;</code>
+     */
+    public Builder addApplicationProtocolsBytes(
+        com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  checkByteStringIsUtf8(value);
+      ensureApplicationProtocolsIsMutable();
+      applicationProtocols_.add(value);
+      onChanged();
+      return this;
+    }
+
+    private com.google.protobuf.LazyStringList recordProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
+    private void ensureRecordProtocolsIsMutable() {
+      if (!((bitField0_ & 0x00000004) == 0x00000004)) {
+        recordProtocols_ = new com.google.protobuf.LazyStringArrayList(recordProtocols_);
+        bitField0_ |= 0x00000004;
+       }
+    }
+    /**
+     * <pre>
+     * The record protocols supported by the client, e.g.,
+     * "ALTSRP_GCM_AES128".
+     * </pre>
+     *
+     * <code>repeated string record_protocols = 3;</code>
+     */
+    public com.google.protobuf.ProtocolStringList
+        getRecordProtocolsList() {
+      return recordProtocols_.getUnmodifiableView();
+    }
+    /**
+     * <pre>
+     * The record protocols supported by the client, e.g.,
+     * "ALTSRP_GCM_AES128".
+     * </pre>
+     *
+     * <code>repeated string record_protocols = 3;</code>
+     */
+    public int getRecordProtocolsCount() {
+      return recordProtocols_.size();
+    }
+    /**
+     * <pre>
+     * The record protocols supported by the client, e.g.,
+     * "ALTSRP_GCM_AES128".
+     * </pre>
+     *
+     * <code>repeated string record_protocols = 3;</code>
+     */
+    public java.lang.String getRecordProtocols(int index) {
+      return recordProtocols_.get(index);
+    }
+    /**
+     * <pre>
+     * The record protocols supported by the client, e.g.,
+     * "ALTSRP_GCM_AES128".
+     * </pre>
+     *
+     * <code>repeated string record_protocols = 3;</code>
+     */
+    public com.google.protobuf.ByteString
+        getRecordProtocolsBytes(int index) {
+      return recordProtocols_.getByteString(index);
+    }
+    /**
+     * <pre>
+     * The record protocols supported by the client, e.g.,
+     * "ALTSRP_GCM_AES128".
+     * </pre>
+     *
+     * <code>repeated string record_protocols = 3;</code>
+     */
+    public Builder setRecordProtocols(
+        int index, java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  ensureRecordProtocolsIsMutable();
+      recordProtocols_.set(index, value);
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The record protocols supported by the client, e.g.,
+     * "ALTSRP_GCM_AES128".
+     * </pre>
+     *
+     * <code>repeated string record_protocols = 3;</code>
+     */
+    public Builder addRecordProtocols(
+        java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  ensureRecordProtocolsIsMutable();
+      recordProtocols_.add(value);
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The record protocols supported by the client, e.g.,
+     * "ALTSRP_GCM_AES128".
+     * </pre>
+     *
+     * <code>repeated string record_protocols = 3;</code>
+     */
+    public Builder addAllRecordProtocols(
+        java.lang.Iterable<java.lang.String> values) {
+      ensureRecordProtocolsIsMutable();
+      com.google.protobuf.AbstractMessageLite.Builder.addAll(
+          values, recordProtocols_);
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The record protocols supported by the client, e.g.,
+     * "ALTSRP_GCM_AES128".
+     * </pre>
+     *
+     * <code>repeated string record_protocols = 3;</code>
+     */
+    public Builder clearRecordProtocols() {
+      recordProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
+      bitField0_ = (bitField0_ & ~0x00000004);
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The record protocols supported by the client, e.g.,
+     * "ALTSRP_GCM_AES128".
+     * </pre>
+     *
+     * <code>repeated string record_protocols = 3;</code>
+     */
+    public Builder addRecordProtocolsBytes(
+        com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  checkByteStringIsUtf8(value);
+      ensureRecordProtocolsIsMutable();
+      recordProtocols_.add(value);
+      onChanged();
+      return this;
+    }
+
+    private java.util.List<io.grpc.alts.internal.Identity> targetIdentities_ =
+      java.util.Collections.emptyList();
+    private void ensureTargetIdentitiesIsMutable() {
+      if (!((bitField0_ & 0x00000008) == 0x00000008)) {
+        targetIdentities_ = new java.util.ArrayList<io.grpc.alts.internal.Identity>(targetIdentities_);
+        bitField0_ |= 0x00000008;
+       }
+    }
+
+    private com.google.protobuf.RepeatedFieldBuilderV3<
+        io.grpc.alts.internal.Identity, io.grpc.alts.internal.Identity.Builder, io.grpc.alts.internal.IdentityOrBuilder> targetIdentitiesBuilder_;
+
+    /**
+     * <pre>
+     * (Optional) Describes which server identities are acceptable by the client.
+     * If target identities are provided and none of them matches the peer
+     * identity of the server, handshake will fail.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+     */
+    public java.util.List<io.grpc.alts.internal.Identity> getTargetIdentitiesList() {
+      if (targetIdentitiesBuilder_ == null) {
+        return java.util.Collections.unmodifiableList(targetIdentities_);
+      } else {
+        return targetIdentitiesBuilder_.getMessageList();
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) Describes which server identities are acceptable by the client.
+     * If target identities are provided and none of them matches the peer
+     * identity of the server, handshake will fail.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+     */
+    public int getTargetIdentitiesCount() {
+      if (targetIdentitiesBuilder_ == null) {
+        return targetIdentities_.size();
+      } else {
+        return targetIdentitiesBuilder_.getCount();
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) Describes which server identities are acceptable by the client.
+     * If target identities are provided and none of them matches the peer
+     * identity of the server, handshake will fail.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+     */
+    public io.grpc.alts.internal.Identity getTargetIdentities(int index) {
+      if (targetIdentitiesBuilder_ == null) {
+        return targetIdentities_.get(index);
+      } else {
+        return targetIdentitiesBuilder_.getMessage(index);
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) Describes which server identities are acceptable by the client.
+     * If target identities are provided and none of them matches the peer
+     * identity of the server, handshake will fail.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+     */
+    public Builder setTargetIdentities(
+        int index, io.grpc.alts.internal.Identity value) {
+      if (targetIdentitiesBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        ensureTargetIdentitiesIsMutable();
+        targetIdentities_.set(index, value);
+        onChanged();
+      } else {
+        targetIdentitiesBuilder_.setMessage(index, value);
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Describes which server identities are acceptable by the client.
+     * If target identities are provided and none of them matches the peer
+     * identity of the server, handshake will fail.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+     */
+    public Builder setTargetIdentities(
+        int index, io.grpc.alts.internal.Identity.Builder builderForValue) {
+      if (targetIdentitiesBuilder_ == null) {
+        ensureTargetIdentitiesIsMutable();
+        targetIdentities_.set(index, builderForValue.build());
+        onChanged();
+      } else {
+        targetIdentitiesBuilder_.setMessage(index, builderForValue.build());
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Describes which server identities are acceptable by the client.
+     * If target identities are provided and none of them matches the peer
+     * identity of the server, handshake will fail.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+     */
+    public Builder addTargetIdentities(io.grpc.alts.internal.Identity value) {
+      if (targetIdentitiesBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        ensureTargetIdentitiesIsMutable();
+        targetIdentities_.add(value);
+        onChanged();
+      } else {
+        targetIdentitiesBuilder_.addMessage(value);
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Describes which server identities are acceptable by the client.
+     * If target identities are provided and none of them matches the peer
+     * identity of the server, handshake will fail.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+     */
+    public Builder addTargetIdentities(
+        int index, io.grpc.alts.internal.Identity value) {
+      if (targetIdentitiesBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        ensureTargetIdentitiesIsMutable();
+        targetIdentities_.add(index, value);
+        onChanged();
+      } else {
+        targetIdentitiesBuilder_.addMessage(index, value);
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Describes which server identities are acceptable by the client.
+     * If target identities are provided and none of them matches the peer
+     * identity of the server, handshake will fail.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+     */
+    public Builder addTargetIdentities(
+        io.grpc.alts.internal.Identity.Builder builderForValue) {
+      if (targetIdentitiesBuilder_ == null) {
+        ensureTargetIdentitiesIsMutable();
+        targetIdentities_.add(builderForValue.build());
+        onChanged();
+      } else {
+        targetIdentitiesBuilder_.addMessage(builderForValue.build());
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Describes which server identities are acceptable by the client.
+     * If target identities are provided and none of them matches the peer
+     * identity of the server, handshake will fail.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+     */
+    public Builder addTargetIdentities(
+        int index, io.grpc.alts.internal.Identity.Builder builderForValue) {
+      if (targetIdentitiesBuilder_ == null) {
+        ensureTargetIdentitiesIsMutable();
+        targetIdentities_.add(index, builderForValue.build());
+        onChanged();
+      } else {
+        targetIdentitiesBuilder_.addMessage(index, builderForValue.build());
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Describes which server identities are acceptable by the client.
+     * If target identities are provided and none of them matches the peer
+     * identity of the server, handshake will fail.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+     */
+    public Builder addAllTargetIdentities(
+        java.lang.Iterable<? extends io.grpc.alts.internal.Identity> values) {
+      if (targetIdentitiesBuilder_ == null) {
+        ensureTargetIdentitiesIsMutable();
+        com.google.protobuf.AbstractMessageLite.Builder.addAll(
+            values, targetIdentities_);
+        onChanged();
+      } else {
+        targetIdentitiesBuilder_.addAllMessages(values);
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Describes which server identities are acceptable by the client.
+     * If target identities are provided and none of them matches the peer
+     * identity of the server, handshake will fail.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+     */
+    public Builder clearTargetIdentities() {
+      if (targetIdentitiesBuilder_ == null) {
+        targetIdentities_ = java.util.Collections.emptyList();
+        bitField0_ = (bitField0_ & ~0x00000008);
+        onChanged();
+      } else {
+        targetIdentitiesBuilder_.clear();
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Describes which server identities are acceptable by the client.
+     * If target identities are provided and none of them matches the peer
+     * identity of the server, handshake will fail.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+     */
+    public Builder removeTargetIdentities(int index) {
+      if (targetIdentitiesBuilder_ == null) {
+        ensureTargetIdentitiesIsMutable();
+        targetIdentities_.remove(index);
+        onChanged();
+      } else {
+        targetIdentitiesBuilder_.remove(index);
+      }
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Describes which server identities are acceptable by the client.
+     * If target identities are provided and none of them matches the peer
+     * identity of the server, handshake will fail.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+     */
+    public io.grpc.alts.internal.Identity.Builder getTargetIdentitiesBuilder(
+        int index) {
+      return getTargetIdentitiesFieldBuilder().getBuilder(index);
+    }
+    /**
+     * <pre>
+     * (Optional) Describes which server identities are acceptable by the client.
+     * If target identities are provided and none of them matches the peer
+     * identity of the server, handshake will fail.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+     */
+    public io.grpc.alts.internal.IdentityOrBuilder getTargetIdentitiesOrBuilder(
+        int index) {
+      if (targetIdentitiesBuilder_ == null) {
+        return targetIdentities_.get(index);  } else {
+        return targetIdentitiesBuilder_.getMessageOrBuilder(index);
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) Describes which server identities are acceptable by the client.
+     * If target identities are provided and none of them matches the peer
+     * identity of the server, handshake will fail.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+     */
+    public java.util.List<? extends io.grpc.alts.internal.IdentityOrBuilder> 
+         getTargetIdentitiesOrBuilderList() {
+      if (targetIdentitiesBuilder_ != null) {
+        return targetIdentitiesBuilder_.getMessageOrBuilderList();
+      } else {
+        return java.util.Collections.unmodifiableList(targetIdentities_);
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) Describes which server identities are acceptable by the client.
+     * If target identities are provided and none of them matches the peer
+     * identity of the server, handshake will fail.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+     */
+    public io.grpc.alts.internal.Identity.Builder addTargetIdentitiesBuilder() {
+      return getTargetIdentitiesFieldBuilder().addBuilder(
+          io.grpc.alts.internal.Identity.getDefaultInstance());
+    }
+    /**
+     * <pre>
+     * (Optional) Describes which server identities are acceptable by the client.
+     * If target identities are provided and none of them matches the peer
+     * identity of the server, handshake will fail.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+     */
+    public io.grpc.alts.internal.Identity.Builder addTargetIdentitiesBuilder(
+        int index) {
+      return getTargetIdentitiesFieldBuilder().addBuilder(
+          index, io.grpc.alts.internal.Identity.getDefaultInstance());
+    }
+    /**
+     * <pre>
+     * (Optional) Describes which server identities are acceptable by the client.
+     * If target identities are provided and none of them matches the peer
+     * identity of the server, handshake will fail.
+     * </pre>
+     *
+     * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+     */
+    public java.util.List<io.grpc.alts.internal.Identity.Builder> 
+         getTargetIdentitiesBuilderList() {
+      return getTargetIdentitiesFieldBuilder().getBuilderList();
+    }
+    private com.google.protobuf.RepeatedFieldBuilderV3<
+        io.grpc.alts.internal.Identity, io.grpc.alts.internal.Identity.Builder, io.grpc.alts.internal.IdentityOrBuilder> 
+        getTargetIdentitiesFieldBuilder() {
+      if (targetIdentitiesBuilder_ == null) {
+        targetIdentitiesBuilder_ = new com.google.protobuf.RepeatedFieldBuilderV3<
+            io.grpc.alts.internal.Identity, io.grpc.alts.internal.Identity.Builder, io.grpc.alts.internal.IdentityOrBuilder>(
+                targetIdentities_,
+                ((bitField0_ & 0x00000008) == 0x00000008),
+                getParentForChildren(),
+                isClean());
+        targetIdentities_ = null;
+      }
+      return targetIdentitiesBuilder_;
+    }
+
+    private io.grpc.alts.internal.Identity localIdentity_ = null;
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.Identity, io.grpc.alts.internal.Identity.Builder, io.grpc.alts.internal.IdentityOrBuilder> localIdentityBuilder_;
+    /**
+     * <pre>
+     * (Optional) Application may specify a local identity. Otherwise, the
+     * handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity local_identity = 5;</code>
+     */
+    public boolean hasLocalIdentity() {
+      return localIdentityBuilder_ != null || localIdentity_ != null;
+    }
+    /**
+     * <pre>
+     * (Optional) Application may specify a local identity. Otherwise, the
+     * handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity local_identity = 5;</code>
+     */
+    public io.grpc.alts.internal.Identity getLocalIdentity() {
+      if (localIdentityBuilder_ == null) {
+        return localIdentity_ == null ? io.grpc.alts.internal.Identity.getDefaultInstance() : localIdentity_;
+      } else {
+        return localIdentityBuilder_.getMessage();
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) Application may specify a local identity. Otherwise, the
+     * handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity local_identity = 5;</code>
+     */
+    public Builder setLocalIdentity(io.grpc.alts.internal.Identity value) {
+      if (localIdentityBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        localIdentity_ = value;
+        onChanged();
+      } else {
+        localIdentityBuilder_.setMessage(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Application may specify a local identity. Otherwise, the
+     * handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity local_identity = 5;</code>
+     */
+    public Builder setLocalIdentity(
+        io.grpc.alts.internal.Identity.Builder builderForValue) {
+      if (localIdentityBuilder_ == null) {
+        localIdentity_ = builderForValue.build();
+        onChanged();
+      } else {
+        localIdentityBuilder_.setMessage(builderForValue.build());
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Application may specify a local identity. Otherwise, the
+     * handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity local_identity = 5;</code>
+     */
+    public Builder mergeLocalIdentity(io.grpc.alts.internal.Identity value) {
+      if (localIdentityBuilder_ == null) {
+        if (localIdentity_ != null) {
+          localIdentity_ =
+            io.grpc.alts.internal.Identity.newBuilder(localIdentity_).mergeFrom(value).buildPartial();
+        } else {
+          localIdentity_ = value;
+        }
+        onChanged();
+      } else {
+        localIdentityBuilder_.mergeFrom(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Application may specify a local identity. Otherwise, the
+     * handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity local_identity = 5;</code>
+     */
+    public Builder clearLocalIdentity() {
+      if (localIdentityBuilder_ == null) {
+        localIdentity_ = null;
+        onChanged();
+      } else {
+        localIdentity_ = null;
+        localIdentityBuilder_ = null;
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Application may specify a local identity. Otherwise, the
+     * handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity local_identity = 5;</code>
+     */
+    public io.grpc.alts.internal.Identity.Builder getLocalIdentityBuilder() {
+      
+      onChanged();
+      return getLocalIdentityFieldBuilder().getBuilder();
+    }
+    /**
+     * <pre>
+     * (Optional) Application may specify a local identity. Otherwise, the
+     * handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity local_identity = 5;</code>
+     */
+    public io.grpc.alts.internal.IdentityOrBuilder getLocalIdentityOrBuilder() {
+      if (localIdentityBuilder_ != null) {
+        return localIdentityBuilder_.getMessageOrBuilder();
+      } else {
+        return localIdentity_ == null ?
+            io.grpc.alts.internal.Identity.getDefaultInstance() : localIdentity_;
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) Application may specify a local identity. Otherwise, the
+     * handshaker chooses a default local identity.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Identity local_identity = 5;</code>
+     */
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.Identity, io.grpc.alts.internal.Identity.Builder, io.grpc.alts.internal.IdentityOrBuilder> 
+        getLocalIdentityFieldBuilder() {
+      if (localIdentityBuilder_ == null) {
+        localIdentityBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
+            io.grpc.alts.internal.Identity, io.grpc.alts.internal.Identity.Builder, io.grpc.alts.internal.IdentityOrBuilder>(
+                getLocalIdentity(),
+                getParentForChildren(),
+                isClean());
+        localIdentity_ = null;
+      }
+      return localIdentityBuilder_;
+    }
+
+    private io.grpc.alts.internal.Endpoint localEndpoint_ = null;
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.Endpoint, io.grpc.alts.internal.Endpoint.Builder, io.grpc.alts.internal.EndpointOrBuilder> localEndpointBuilder_;
+    /**
+     * <pre>
+     * (Optional) Local endpoint information of the connection to the server,
+     * such as local IP address, port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
+     */
+    public boolean hasLocalEndpoint() {
+      return localEndpointBuilder_ != null || localEndpoint_ != null;
+    }
+    /**
+     * <pre>
+     * (Optional) Local endpoint information of the connection to the server,
+     * such as local IP address, port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
+     */
+    public io.grpc.alts.internal.Endpoint getLocalEndpoint() {
+      if (localEndpointBuilder_ == null) {
+        return localEndpoint_ == null ? io.grpc.alts.internal.Endpoint.getDefaultInstance() : localEndpoint_;
+      } else {
+        return localEndpointBuilder_.getMessage();
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) Local endpoint information of the connection to the server,
+     * such as local IP address, port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
+     */
+    public Builder setLocalEndpoint(io.grpc.alts.internal.Endpoint value) {
+      if (localEndpointBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        localEndpoint_ = value;
+        onChanged();
+      } else {
+        localEndpointBuilder_.setMessage(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Local endpoint information of the connection to the server,
+     * such as local IP address, port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
+     */
+    public Builder setLocalEndpoint(
+        io.grpc.alts.internal.Endpoint.Builder builderForValue) {
+      if (localEndpointBuilder_ == null) {
+        localEndpoint_ = builderForValue.build();
+        onChanged();
+      } else {
+        localEndpointBuilder_.setMessage(builderForValue.build());
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Local endpoint information of the connection to the server,
+     * such as local IP address, port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
+     */
+    public Builder mergeLocalEndpoint(io.grpc.alts.internal.Endpoint value) {
+      if (localEndpointBuilder_ == null) {
+        if (localEndpoint_ != null) {
+          localEndpoint_ =
+            io.grpc.alts.internal.Endpoint.newBuilder(localEndpoint_).mergeFrom(value).buildPartial();
+        } else {
+          localEndpoint_ = value;
+        }
+        onChanged();
+      } else {
+        localEndpointBuilder_.mergeFrom(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Local endpoint information of the connection to the server,
+     * such as local IP address, port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
+     */
+    public Builder clearLocalEndpoint() {
+      if (localEndpointBuilder_ == null) {
+        localEndpoint_ = null;
+        onChanged();
+      } else {
+        localEndpoint_ = null;
+        localEndpointBuilder_ = null;
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Local endpoint information of the connection to the server,
+     * such as local IP address, port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
+     */
+    public io.grpc.alts.internal.Endpoint.Builder getLocalEndpointBuilder() {
+      
+      onChanged();
+      return getLocalEndpointFieldBuilder().getBuilder();
+    }
+    /**
+     * <pre>
+     * (Optional) Local endpoint information of the connection to the server,
+     * such as local IP address, port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
+     */
+    public io.grpc.alts.internal.EndpointOrBuilder getLocalEndpointOrBuilder() {
+      if (localEndpointBuilder_ != null) {
+        return localEndpointBuilder_.getMessageOrBuilder();
+      } else {
+        return localEndpoint_ == null ?
+            io.grpc.alts.internal.Endpoint.getDefaultInstance() : localEndpoint_;
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) Local endpoint information of the connection to the server,
+     * such as local IP address, port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
+     */
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.Endpoint, io.grpc.alts.internal.Endpoint.Builder, io.grpc.alts.internal.EndpointOrBuilder> 
+        getLocalEndpointFieldBuilder() {
+      if (localEndpointBuilder_ == null) {
+        localEndpointBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
+            io.grpc.alts.internal.Endpoint, io.grpc.alts.internal.Endpoint.Builder, io.grpc.alts.internal.EndpointOrBuilder>(
+                getLocalEndpoint(),
+                getParentForChildren(),
+                isClean());
+        localEndpoint_ = null;
+      }
+      return localEndpointBuilder_;
+    }
+
+    private io.grpc.alts.internal.Endpoint remoteEndpoint_ = null;
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.Endpoint, io.grpc.alts.internal.Endpoint.Builder, io.grpc.alts.internal.EndpointOrBuilder> remoteEndpointBuilder_;
+    /**
+     * <pre>
+     * (Optional) Endpoint information of the remote server, such as IP address,
+     * port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
+     */
+    public boolean hasRemoteEndpoint() {
+      return remoteEndpointBuilder_ != null || remoteEndpoint_ != null;
+    }
+    /**
+     * <pre>
+     * (Optional) Endpoint information of the remote server, such as IP address,
+     * port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
+     */
+    public io.grpc.alts.internal.Endpoint getRemoteEndpoint() {
+      if (remoteEndpointBuilder_ == null) {
+        return remoteEndpoint_ == null ? io.grpc.alts.internal.Endpoint.getDefaultInstance() : remoteEndpoint_;
+      } else {
+        return remoteEndpointBuilder_.getMessage();
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) Endpoint information of the remote server, such as IP address,
+     * port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
+     */
+    public Builder setRemoteEndpoint(io.grpc.alts.internal.Endpoint value) {
+      if (remoteEndpointBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        remoteEndpoint_ = value;
+        onChanged();
+      } else {
+        remoteEndpointBuilder_.setMessage(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Endpoint information of the remote server, such as IP address,
+     * port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
+     */
+    public Builder setRemoteEndpoint(
+        io.grpc.alts.internal.Endpoint.Builder builderForValue) {
+      if (remoteEndpointBuilder_ == null) {
+        remoteEndpoint_ = builderForValue.build();
+        onChanged();
+      } else {
+        remoteEndpointBuilder_.setMessage(builderForValue.build());
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Endpoint information of the remote server, such as IP address,
+     * port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
+     */
+    public Builder mergeRemoteEndpoint(io.grpc.alts.internal.Endpoint value) {
+      if (remoteEndpointBuilder_ == null) {
+        if (remoteEndpoint_ != null) {
+          remoteEndpoint_ =
+            io.grpc.alts.internal.Endpoint.newBuilder(remoteEndpoint_).mergeFrom(value).buildPartial();
+        } else {
+          remoteEndpoint_ = value;
+        }
+        onChanged();
+      } else {
+        remoteEndpointBuilder_.mergeFrom(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Endpoint information of the remote server, such as IP address,
+     * port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
+     */
+    public Builder clearRemoteEndpoint() {
+      if (remoteEndpointBuilder_ == null) {
+        remoteEndpoint_ = null;
+        onChanged();
+      } else {
+        remoteEndpoint_ = null;
+        remoteEndpointBuilder_ = null;
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Endpoint information of the remote server, such as IP address,
+     * port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
+     */
+    public io.grpc.alts.internal.Endpoint.Builder getRemoteEndpointBuilder() {
+      
+      onChanged();
+      return getRemoteEndpointFieldBuilder().getBuilder();
+    }
+    /**
+     * <pre>
+     * (Optional) Endpoint information of the remote server, such as IP address,
+     * port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
+     */
+    public io.grpc.alts.internal.EndpointOrBuilder getRemoteEndpointOrBuilder() {
+      if (remoteEndpointBuilder_ != null) {
+        return remoteEndpointBuilder_.getMessageOrBuilder();
+      } else {
+        return remoteEndpoint_ == null ?
+            io.grpc.alts.internal.Endpoint.getDefaultInstance() : remoteEndpoint_;
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) Endpoint information of the remote server, such as IP address,
+     * port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
+     */
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.Endpoint, io.grpc.alts.internal.Endpoint.Builder, io.grpc.alts.internal.EndpointOrBuilder> 
+        getRemoteEndpointFieldBuilder() {
+      if (remoteEndpointBuilder_ == null) {
+        remoteEndpointBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
+            io.grpc.alts.internal.Endpoint, io.grpc.alts.internal.Endpoint.Builder, io.grpc.alts.internal.EndpointOrBuilder>(
+                getRemoteEndpoint(),
+                getParentForChildren(),
+                isClean());
+        remoteEndpoint_ = null;
+      }
+      return remoteEndpointBuilder_;
+    }
+
+    private java.lang.Object targetName_ = "";
+    /**
+     * <pre>
+     * (Optional) If target name is provided, a secure naming check is performed
+     * to verify that the peer authenticated identity is indeed authorized to run
+     * the target name.
+     * </pre>
+     *
+     * <code>string target_name = 8;</code>
+     */
+    public java.lang.String getTargetName() {
+      java.lang.Object ref = targetName_;
+      if (!(ref instanceof java.lang.String)) {
+        com.google.protobuf.ByteString bs =
+            (com.google.protobuf.ByteString) ref;
+        java.lang.String s = bs.toStringUtf8();
+        targetName_ = s;
+        return s;
+      } else {
+        return (java.lang.String) ref;
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) If target name is provided, a secure naming check is performed
+     * to verify that the peer authenticated identity is indeed authorized to run
+     * the target name.
+     * </pre>
+     *
+     * <code>string target_name = 8;</code>
+     */
+    public com.google.protobuf.ByteString
+        getTargetNameBytes() {
+      java.lang.Object ref = targetName_;
+      if (ref instanceof String) {
+        com.google.protobuf.ByteString b = 
+            com.google.protobuf.ByteString.copyFromUtf8(
+                (java.lang.String) ref);
+        targetName_ = b;
+        return b;
+      } else {
+        return (com.google.protobuf.ByteString) ref;
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) If target name is provided, a secure naming check is performed
+     * to verify that the peer authenticated identity is indeed authorized to run
+     * the target name.
+     * </pre>
+     *
+     * <code>string target_name = 8;</code>
+     */
+    public Builder setTargetName(
+        java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  
+      targetName_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) If target name is provided, a secure naming check is performed
+     * to verify that the peer authenticated identity is indeed authorized to run
+     * the target name.
+     * </pre>
+     *
+     * <code>string target_name = 8;</code>
+     */
+    public Builder clearTargetName() {
+      
+      targetName_ = getDefaultInstance().getTargetName();
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) If target name is provided, a secure naming check is performed
+     * to verify that the peer authenticated identity is indeed authorized to run
+     * the target name.
+     * </pre>
+     *
+     * <code>string target_name = 8;</code>
+     */
+    public Builder setTargetNameBytes(
+        com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  checkByteStringIsUtf8(value);
+      
+      targetName_ = value;
+      onChanged();
+      return this;
+    }
+
+    private io.grpc.alts.internal.RpcProtocolVersions rpcVersions_ = null;
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.RpcProtocolVersions, io.grpc.alts.internal.RpcProtocolVersions.Builder, io.grpc.alts.internal.RpcProtocolVersionsOrBuilder> rpcVersionsBuilder_;
+    /**
+     * <pre>
+     * (Optional) RPC protocol versions supported by the client.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
+     */
+    public boolean hasRpcVersions() {
+      return rpcVersionsBuilder_ != null || rpcVersions_ != null;
+    }
+    /**
+     * <pre>
+     * (Optional) RPC protocol versions supported by the client.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
+     */
+    public io.grpc.alts.internal.RpcProtocolVersions getRpcVersions() {
+      if (rpcVersionsBuilder_ == null) {
+        return rpcVersions_ == null ? io.grpc.alts.internal.RpcProtocolVersions.getDefaultInstance() : rpcVersions_;
+      } else {
+        return rpcVersionsBuilder_.getMessage();
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) RPC protocol versions supported by the client.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
+     */
+    public Builder setRpcVersions(io.grpc.alts.internal.RpcProtocolVersions value) {
+      if (rpcVersionsBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        rpcVersions_ = value;
+        onChanged();
+      } else {
+        rpcVersionsBuilder_.setMessage(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) RPC protocol versions supported by the client.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
+     */
+    public Builder setRpcVersions(
+        io.grpc.alts.internal.RpcProtocolVersions.Builder builderForValue) {
+      if (rpcVersionsBuilder_ == null) {
+        rpcVersions_ = builderForValue.build();
+        onChanged();
+      } else {
+        rpcVersionsBuilder_.setMessage(builderForValue.build());
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) RPC protocol versions supported by the client.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
+     */
+    public Builder mergeRpcVersions(io.grpc.alts.internal.RpcProtocolVersions value) {
+      if (rpcVersionsBuilder_ == null) {
+        if (rpcVersions_ != null) {
+          rpcVersions_ =
+            io.grpc.alts.internal.RpcProtocolVersions.newBuilder(rpcVersions_).mergeFrom(value).buildPartial();
+        } else {
+          rpcVersions_ = value;
+        }
+        onChanged();
+      } else {
+        rpcVersionsBuilder_.mergeFrom(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) RPC protocol versions supported by the client.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
+     */
+    public Builder clearRpcVersions() {
+      if (rpcVersionsBuilder_ == null) {
+        rpcVersions_ = null;
+        onChanged();
+      } else {
+        rpcVersions_ = null;
+        rpcVersionsBuilder_ = null;
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) RPC protocol versions supported by the client.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
+     */
+    public io.grpc.alts.internal.RpcProtocolVersions.Builder getRpcVersionsBuilder() {
+      
+      onChanged();
+      return getRpcVersionsFieldBuilder().getBuilder();
+    }
+    /**
+     * <pre>
+     * (Optional) RPC protocol versions supported by the client.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
+     */
+    public io.grpc.alts.internal.RpcProtocolVersionsOrBuilder getRpcVersionsOrBuilder() {
+      if (rpcVersionsBuilder_ != null) {
+        return rpcVersionsBuilder_.getMessageOrBuilder();
+      } else {
+        return rpcVersions_ == null ?
+            io.grpc.alts.internal.RpcProtocolVersions.getDefaultInstance() : rpcVersions_;
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) RPC protocol versions supported by the client.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
+     */
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.RpcProtocolVersions, io.grpc.alts.internal.RpcProtocolVersions.Builder, io.grpc.alts.internal.RpcProtocolVersionsOrBuilder> 
+        getRpcVersionsFieldBuilder() {
+      if (rpcVersionsBuilder_ == null) {
+        rpcVersionsBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
+            io.grpc.alts.internal.RpcProtocolVersions, io.grpc.alts.internal.RpcProtocolVersions.Builder, io.grpc.alts.internal.RpcProtocolVersionsOrBuilder>(
+                getRpcVersions(),
+                getParentForChildren(),
+                isClean());
+        rpcVersions_ = null;
+      }
+      return rpcVersionsBuilder_;
+    }
+    public final Builder setUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.setUnknownFieldsProto3(unknownFields);
+    }
+
+    public final Builder mergeUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.mergeUnknownFields(unknownFields);
+    }
+
+
+    // @@protoc_insertion_point(builder_scope:grpc.gcp.StartClientHandshakeReq)
+  }
+
+  // @@protoc_insertion_point(class_scope:grpc.gcp.StartClientHandshakeReq)
+  private static final io.grpc.alts.internal.StartClientHandshakeReq DEFAULT_INSTANCE;
+  static {
+    DEFAULT_INSTANCE = new io.grpc.alts.internal.StartClientHandshakeReq();
+  }
+
+  public static io.grpc.alts.internal.StartClientHandshakeReq getDefaultInstance() {
+    return DEFAULT_INSTANCE;
+  }
+
+  private static final com.google.protobuf.Parser<StartClientHandshakeReq>
+      PARSER = new com.google.protobuf.AbstractParser<StartClientHandshakeReq>() {
+    public StartClientHandshakeReq parsePartialFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return new StartClientHandshakeReq(input, extensionRegistry);
+    }
+  };
+
+  public static com.google.protobuf.Parser<StartClientHandshakeReq> parser() {
+    return PARSER;
+  }
+
+  @java.lang.Override
+  public com.google.protobuf.Parser<StartClientHandshakeReq> getParserForType() {
+    return PARSER;
+  }
+
+  public io.grpc.alts.internal.StartClientHandshakeReq getDefaultInstanceForType() {
+    return DEFAULT_INSTANCE;
+  }
+
+}
+
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/StartClientHandshakeReqOrBuilder.java b/alts/src/generated/main/java/io/grpc/alts/internal/StartClientHandshakeReqOrBuilder.java
new file mode 100644
index 0000000000..7c483c4d94
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/StartClientHandshakeReqOrBuilder.java
@@ -0,0 +1,289 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+public interface StartClientHandshakeReqOrBuilder extends
+    // @@protoc_insertion_point(interface_extends:grpc.gcp.StartClientHandshakeReq)
+    com.google.protobuf.MessageOrBuilder {
+
+  /**
+   * <pre>
+   * Handshake security protocol requested by the client.
+   * </pre>
+   *
+   * <code>.grpc.gcp.HandshakeProtocol handshake_security_protocol = 1;</code>
+   */
+  int getHandshakeSecurityProtocolValue();
+  /**
+   * <pre>
+   * Handshake security protocol requested by the client.
+   * </pre>
+   *
+   * <code>.grpc.gcp.HandshakeProtocol handshake_security_protocol = 1;</code>
+   */
+  io.grpc.alts.internal.HandshakeProtocol getHandshakeSecurityProtocol();
+
+  /**
+   * <pre>
+   * The application protocols supported by the client, e.g., "h2" (for http2),
+   * "grpc".
+   * </pre>
+   *
+   * <code>repeated string application_protocols = 2;</code>
+   */
+  java.util.List<java.lang.String>
+      getApplicationProtocolsList();
+  /**
+   * <pre>
+   * The application protocols supported by the client, e.g., "h2" (for http2),
+   * "grpc".
+   * </pre>
+   *
+   * <code>repeated string application_protocols = 2;</code>
+   */
+  int getApplicationProtocolsCount();
+  /**
+   * <pre>
+   * The application protocols supported by the client, e.g., "h2" (for http2),
+   * "grpc".
+   * </pre>
+   *
+   * <code>repeated string application_protocols = 2;</code>
+   */
+  java.lang.String getApplicationProtocols(int index);
+  /**
+   * <pre>
+   * The application protocols supported by the client, e.g., "h2" (for http2),
+   * "grpc".
+   * </pre>
+   *
+   * <code>repeated string application_protocols = 2;</code>
+   */
+  com.google.protobuf.ByteString
+      getApplicationProtocolsBytes(int index);
+
+  /**
+   * <pre>
+   * The record protocols supported by the client, e.g.,
+   * "ALTSRP_GCM_AES128".
+   * </pre>
+   *
+   * <code>repeated string record_protocols = 3;</code>
+   */
+  java.util.List<java.lang.String>
+      getRecordProtocolsList();
+  /**
+   * <pre>
+   * The record protocols supported by the client, e.g.,
+   * "ALTSRP_GCM_AES128".
+   * </pre>
+   *
+   * <code>repeated string record_protocols = 3;</code>
+   */
+  int getRecordProtocolsCount();
+  /**
+   * <pre>
+   * The record protocols supported by the client, e.g.,
+   * "ALTSRP_GCM_AES128".
+   * </pre>
+   *
+   * <code>repeated string record_protocols = 3;</code>
+   */
+  java.lang.String getRecordProtocols(int index);
+  /**
+   * <pre>
+   * The record protocols supported by the client, e.g.,
+   * "ALTSRP_GCM_AES128".
+   * </pre>
+   *
+   * <code>repeated string record_protocols = 3;</code>
+   */
+  com.google.protobuf.ByteString
+      getRecordProtocolsBytes(int index);
+
+  /**
+   * <pre>
+   * (Optional) Describes which server identities are acceptable by the client.
+   * If target identities are provided and none of them matches the peer
+   * identity of the server, handshake will fail.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+   */
+  java.util.List<io.grpc.alts.internal.Identity> 
+      getTargetIdentitiesList();
+  /**
+   * <pre>
+   * (Optional) Describes which server identities are acceptable by the client.
+   * If target identities are provided and none of them matches the peer
+   * identity of the server, handshake will fail.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+   */
+  io.grpc.alts.internal.Identity getTargetIdentities(int index);
+  /**
+   * <pre>
+   * (Optional) Describes which server identities are acceptable by the client.
+   * If target identities are provided and none of them matches the peer
+   * identity of the server, handshake will fail.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+   */
+  int getTargetIdentitiesCount();
+  /**
+   * <pre>
+   * (Optional) Describes which server identities are acceptable by the client.
+   * If target identities are provided and none of them matches the peer
+   * identity of the server, handshake will fail.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+   */
+  java.util.List<? extends io.grpc.alts.internal.IdentityOrBuilder> 
+      getTargetIdentitiesOrBuilderList();
+  /**
+   * <pre>
+   * (Optional) Describes which server identities are acceptable by the client.
+   * If target identities are provided and none of them matches the peer
+   * identity of the server, handshake will fail.
+   * </pre>
+   *
+   * <code>repeated .grpc.gcp.Identity target_identities = 4;</code>
+   */
+  io.grpc.alts.internal.IdentityOrBuilder getTargetIdentitiesOrBuilder(
+      int index);
+
+  /**
+   * <pre>
+   * (Optional) Application may specify a local identity. Otherwise, the
+   * handshaker chooses a default local identity.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Identity local_identity = 5;</code>
+   */
+  boolean hasLocalIdentity();
+  /**
+   * <pre>
+   * (Optional) Application may specify a local identity. Otherwise, the
+   * handshaker chooses a default local identity.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Identity local_identity = 5;</code>
+   */
+  io.grpc.alts.internal.Identity getLocalIdentity();
+  /**
+   * <pre>
+   * (Optional) Application may specify a local identity. Otherwise, the
+   * handshaker chooses a default local identity.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Identity local_identity = 5;</code>
+   */
+  io.grpc.alts.internal.IdentityOrBuilder getLocalIdentityOrBuilder();
+
+  /**
+   * <pre>
+   * (Optional) Local endpoint information of the connection to the server,
+   * such as local IP address, port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
+   */
+  boolean hasLocalEndpoint();
+  /**
+   * <pre>
+   * (Optional) Local endpoint information of the connection to the server,
+   * such as local IP address, port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
+   */
+  io.grpc.alts.internal.Endpoint getLocalEndpoint();
+  /**
+   * <pre>
+   * (Optional) Local endpoint information of the connection to the server,
+   * such as local IP address, port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint local_endpoint = 6;</code>
+   */
+  io.grpc.alts.internal.EndpointOrBuilder getLocalEndpointOrBuilder();
+
+  /**
+   * <pre>
+   * (Optional) Endpoint information of the remote server, such as IP address,
+   * port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
+   */
+  boolean hasRemoteEndpoint();
+  /**
+   * <pre>
+   * (Optional) Endpoint information of the remote server, such as IP address,
+   * port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
+   */
+  io.grpc.alts.internal.Endpoint getRemoteEndpoint();
+  /**
+   * <pre>
+   * (Optional) Endpoint information of the remote server, such as IP address,
+   * port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint remote_endpoint = 7;</code>
+   */
+  io.grpc.alts.internal.EndpointOrBuilder getRemoteEndpointOrBuilder();
+
+  /**
+   * <pre>
+   * (Optional) If target name is provided, a secure naming check is performed
+   * to verify that the peer authenticated identity is indeed authorized to run
+   * the target name.
+   * </pre>
+   *
+   * <code>string target_name = 8;</code>
+   */
+  java.lang.String getTargetName();
+  /**
+   * <pre>
+   * (Optional) If target name is provided, a secure naming check is performed
+   * to verify that the peer authenticated identity is indeed authorized to run
+   * the target name.
+   * </pre>
+   *
+   * <code>string target_name = 8;</code>
+   */
+  com.google.protobuf.ByteString
+      getTargetNameBytes();
+
+  /**
+   * <pre>
+   * (Optional) RPC protocol versions supported by the client.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
+   */
+  boolean hasRpcVersions();
+  /**
+   * <pre>
+   * (Optional) RPC protocol versions supported by the client.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
+   */
+  io.grpc.alts.internal.RpcProtocolVersions getRpcVersions();
+  /**
+   * <pre>
+   * (Optional) RPC protocol versions supported by the client.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 9;</code>
+   */
+  io.grpc.alts.internal.RpcProtocolVersionsOrBuilder getRpcVersionsOrBuilder();
+}
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/StartServerHandshakeReq.java b/alts/src/generated/main/java/io/grpc/alts/internal/StartServerHandshakeReq.java
new file mode 100644
index 0000000000..7a4bc171c9
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/StartServerHandshakeReq.java
@@ -0,0 +1,1781 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+/**
+ * Protobuf type {@code grpc.gcp.StartServerHandshakeReq}
+ */
+public  final class StartServerHandshakeReq extends
+    com.google.protobuf.GeneratedMessageV3 implements
+    // @@protoc_insertion_point(message_implements:grpc.gcp.StartServerHandshakeReq)
+    StartServerHandshakeReqOrBuilder {
+private static final long serialVersionUID = 0L;
+  // Use StartServerHandshakeReq.newBuilder() to construct.
+  private StartServerHandshakeReq(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
+    super(builder);
+  }
+  private StartServerHandshakeReq() {
+    applicationProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
+    inBytes_ = com.google.protobuf.ByteString.EMPTY;
+  }
+
+  @java.lang.Override
+  public final com.google.protobuf.UnknownFieldSet
+  getUnknownFields() {
+    return this.unknownFields;
+  }
+  private StartServerHandshakeReq(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    this();
+    if (extensionRegistry == null) {
+      throw new java.lang.NullPointerException();
+    }
+    int mutable_bitField0_ = 0;
+    com.google.protobuf.UnknownFieldSet.Builder unknownFields =
+        com.google.protobuf.UnknownFieldSet.newBuilder();
+    try {
+      boolean done = false;
+      while (!done) {
+        int tag = input.readTag();
+        switch (tag) {
+          case 0:
+            done = true;
+            break;
+          default: {
+            if (!parseUnknownFieldProto3(
+                input, unknownFields, extensionRegistry, tag)) {
+              done = true;
+            }
+            break;
+          }
+          case 10: {
+            java.lang.String s = input.readStringRequireUtf8();
+            if (!((mutable_bitField0_ & 0x00000001) == 0x00000001)) {
+              applicationProtocols_ = new com.google.protobuf.LazyStringArrayList();
+              mutable_bitField0_ |= 0x00000001;
+            }
+            applicationProtocols_.add(s);
+            break;
+          }
+          case 18: {
+            if (!((mutable_bitField0_ & 0x00000002) == 0x00000002)) {
+              handshakeParameters_ = com.google.protobuf.MapField.newMapField(
+                  HandshakeParametersDefaultEntryHolder.defaultEntry);
+              mutable_bitField0_ |= 0x00000002;
+            }
+            com.google.protobuf.MapEntry<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters>
+            handshakeParameters__ = input.readMessage(
+                HandshakeParametersDefaultEntryHolder.defaultEntry.getParserForType(), extensionRegistry);
+            handshakeParameters_.getMutableMap().put(
+                handshakeParameters__.getKey(), handshakeParameters__.getValue());
+            break;
+          }
+          case 26: {
+
+            inBytes_ = input.readBytes();
+            break;
+          }
+          case 34: {
+            io.grpc.alts.internal.Endpoint.Builder subBuilder = null;
+            if (localEndpoint_ != null) {
+              subBuilder = localEndpoint_.toBuilder();
+            }
+            localEndpoint_ = input.readMessage(io.grpc.alts.internal.Endpoint.parser(), extensionRegistry);
+            if (subBuilder != null) {
+              subBuilder.mergeFrom(localEndpoint_);
+              localEndpoint_ = subBuilder.buildPartial();
+            }
+
+            break;
+          }
+          case 42: {
+            io.grpc.alts.internal.Endpoint.Builder subBuilder = null;
+            if (remoteEndpoint_ != null) {
+              subBuilder = remoteEndpoint_.toBuilder();
+            }
+            remoteEndpoint_ = input.readMessage(io.grpc.alts.internal.Endpoint.parser(), extensionRegistry);
+            if (subBuilder != null) {
+              subBuilder.mergeFrom(remoteEndpoint_);
+              remoteEndpoint_ = subBuilder.buildPartial();
+            }
+
+            break;
+          }
+          case 50: {
+            io.grpc.alts.internal.RpcProtocolVersions.Builder subBuilder = null;
+            if (rpcVersions_ != null) {
+              subBuilder = rpcVersions_.toBuilder();
+            }
+            rpcVersions_ = input.readMessage(io.grpc.alts.internal.RpcProtocolVersions.parser(), extensionRegistry);
+            if (subBuilder != null) {
+              subBuilder.mergeFrom(rpcVersions_);
+              rpcVersions_ = subBuilder.buildPartial();
+            }
+
+            break;
+          }
+        }
+      }
+    } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+      throw e.setUnfinishedMessage(this);
+    } catch (java.io.IOException e) {
+      throw new com.google.protobuf.InvalidProtocolBufferException(
+          e).setUnfinishedMessage(this);
+    } finally {
+      if (((mutable_bitField0_ & 0x00000001) == 0x00000001)) {
+        applicationProtocols_ = applicationProtocols_.getUnmodifiableView();
+      }
+      this.unknownFields = unknownFields.build();
+      makeExtensionsImmutable();
+    }
+  }
+  public static final com.google.protobuf.Descriptors.Descriptor
+      getDescriptor() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_StartServerHandshakeReq_descriptor;
+  }
+
+  @SuppressWarnings({"rawtypes"})
+  protected com.google.protobuf.MapField internalGetMapField(
+      int number) {
+    switch (number) {
+      case 2:
+        return internalGetHandshakeParameters();
+      default:
+        throw new RuntimeException(
+            "Invalid map field number: " + number);
+    }
+  }
+  protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internalGetFieldAccessorTable() {
+    return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_StartServerHandshakeReq_fieldAccessorTable
+        .ensureFieldAccessorsInitialized(
+            io.grpc.alts.internal.StartServerHandshakeReq.class, io.grpc.alts.internal.StartServerHandshakeReq.Builder.class);
+  }
+
+  private int bitField0_;
+  public static final int APPLICATION_PROTOCOLS_FIELD_NUMBER = 1;
+  private com.google.protobuf.LazyStringList applicationProtocols_;
+  /**
+   * <pre>
+   * The application protocols supported by the server, e.g., "h2" (for http2),
+   * "grpc".
+   * </pre>
+   *
+   * <code>repeated string application_protocols = 1;</code>
+   */
+  public com.google.protobuf.ProtocolStringList
+      getApplicationProtocolsList() {
+    return applicationProtocols_;
+  }
+  /**
+   * <pre>
+   * The application protocols supported by the server, e.g., "h2" (for http2),
+   * "grpc".
+   * </pre>
+   *
+   * <code>repeated string application_protocols = 1;</code>
+   */
+  public int getApplicationProtocolsCount() {
+    return applicationProtocols_.size();
+  }
+  /**
+   * <pre>
+   * The application protocols supported by the server, e.g., "h2" (for http2),
+   * "grpc".
+   * </pre>
+   *
+   * <code>repeated string application_protocols = 1;</code>
+   */
+  public java.lang.String getApplicationProtocols(int index) {
+    return applicationProtocols_.get(index);
+  }
+  /**
+   * <pre>
+   * The application protocols supported by the server, e.g., "h2" (for http2),
+   * "grpc".
+   * </pre>
+   *
+   * <code>repeated string application_protocols = 1;</code>
+   */
+  public com.google.protobuf.ByteString
+      getApplicationProtocolsBytes(int index) {
+    return applicationProtocols_.getByteString(index);
+  }
+
+  public static final int HANDSHAKE_PARAMETERS_FIELD_NUMBER = 2;
+  private static final class HandshakeParametersDefaultEntryHolder {
+    static final com.google.protobuf.MapEntry<
+        java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters> defaultEntry =
+            com.google.protobuf.MapEntry
+            .<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters>newDefaultInstance(
+                io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_StartServerHandshakeReq_HandshakeParametersEntry_descriptor, 
+                com.google.protobuf.WireFormat.FieldType.INT32,
+                0,
+                com.google.protobuf.WireFormat.FieldType.MESSAGE,
+                io.grpc.alts.internal.ServerHandshakeParameters.getDefaultInstance());
+  }
+  private com.google.protobuf.MapField<
+      java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters> handshakeParameters_;
+  private com.google.protobuf.MapField<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters>
+  internalGetHandshakeParameters() {
+    if (handshakeParameters_ == null) {
+      return com.google.protobuf.MapField.emptyMapField(
+          HandshakeParametersDefaultEntryHolder.defaultEntry);
+    }
+    return handshakeParameters_;
+  }
+
+  public int getHandshakeParametersCount() {
+    return internalGetHandshakeParameters().getMap().size();
+  }
+  /**
+   * <pre>
+   * Handshake parameters (record protocols and local identities supported by
+   * the server) mapped by the handshake protocol. Each handshake security
+   * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
+   * identities. Since protobuf does not support enum as key to the map, the key
+   * to handshake_parameters is the integer value of HandshakeProtocol enum.
+   * </pre>
+   *
+   * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
+   */
+
+  public boolean containsHandshakeParameters(
+      int key) {
+    
+    return internalGetHandshakeParameters().getMap().containsKey(key);
+  }
+  /**
+   * Use {@link #getHandshakeParametersMap()} instead.
+   */
+  @java.lang.Deprecated
+  public java.util.Map<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters> getHandshakeParameters() {
+    return getHandshakeParametersMap();
+  }
+  /**
+   * <pre>
+   * Handshake parameters (record protocols and local identities supported by
+   * the server) mapped by the handshake protocol. Each handshake security
+   * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
+   * identities. Since protobuf does not support enum as key to the map, the key
+   * to handshake_parameters is the integer value of HandshakeProtocol enum.
+   * </pre>
+   *
+   * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
+   */
+
+  public java.util.Map<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters> getHandshakeParametersMap() {
+    return internalGetHandshakeParameters().getMap();
+  }
+  /**
+   * <pre>
+   * Handshake parameters (record protocols and local identities supported by
+   * the server) mapped by the handshake protocol. Each handshake security
+   * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
+   * identities. Since protobuf does not support enum as key to the map, the key
+   * to handshake_parameters is the integer value of HandshakeProtocol enum.
+   * </pre>
+   *
+   * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
+   */
+
+  public io.grpc.alts.internal.ServerHandshakeParameters getHandshakeParametersOrDefault(
+      int key,
+      io.grpc.alts.internal.ServerHandshakeParameters defaultValue) {
+    
+    java.util.Map<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters> map =
+        internalGetHandshakeParameters().getMap();
+    return map.containsKey(key) ? map.get(key) : defaultValue;
+  }
+  /**
+   * <pre>
+   * Handshake parameters (record protocols and local identities supported by
+   * the server) mapped by the handshake protocol. Each handshake security
+   * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
+   * identities. Since protobuf does not support enum as key to the map, the key
+   * to handshake_parameters is the integer value of HandshakeProtocol enum.
+   * </pre>
+   *
+   * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
+   */
+
+  public io.grpc.alts.internal.ServerHandshakeParameters getHandshakeParametersOrThrow(
+      int key) {
+    
+    java.util.Map<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters> map =
+        internalGetHandshakeParameters().getMap();
+    if (!map.containsKey(key)) {
+      throw new java.lang.IllegalArgumentException();
+    }
+    return map.get(key);
+  }
+
+  public static final int IN_BYTES_FIELD_NUMBER = 3;
+  private com.google.protobuf.ByteString inBytes_;
+  /**
+   * <pre>
+   * Bytes in out_frames returned from the peer's HandshakerResp. It is possible
+   * that the peer's out_frames are split into multiple HandshakReq messages.
+   * </pre>
+   *
+   * <code>bytes in_bytes = 3;</code>
+   */
+  public com.google.protobuf.ByteString getInBytes() {
+    return inBytes_;
+  }
+
+  public static final int LOCAL_ENDPOINT_FIELD_NUMBER = 4;
+  private io.grpc.alts.internal.Endpoint localEndpoint_;
+  /**
+   * <pre>
+   * (Optional) Local endpoint information of the connection to the client,
+   * such as local IP address, port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
+   */
+  public boolean hasLocalEndpoint() {
+    return localEndpoint_ != null;
+  }
+  /**
+   * <pre>
+   * (Optional) Local endpoint information of the connection to the client,
+   * such as local IP address, port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
+   */
+  public io.grpc.alts.internal.Endpoint getLocalEndpoint() {
+    return localEndpoint_ == null ? io.grpc.alts.internal.Endpoint.getDefaultInstance() : localEndpoint_;
+  }
+  /**
+   * <pre>
+   * (Optional) Local endpoint information of the connection to the client,
+   * such as local IP address, port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
+   */
+  public io.grpc.alts.internal.EndpointOrBuilder getLocalEndpointOrBuilder() {
+    return getLocalEndpoint();
+  }
+
+  public static final int REMOTE_ENDPOINT_FIELD_NUMBER = 5;
+  private io.grpc.alts.internal.Endpoint remoteEndpoint_;
+  /**
+   * <pre>
+   * (Optional) Endpoint information of the remote client, such as IP address,
+   * port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
+   */
+  public boolean hasRemoteEndpoint() {
+    return remoteEndpoint_ != null;
+  }
+  /**
+   * <pre>
+   * (Optional) Endpoint information of the remote client, such as IP address,
+   * port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
+   */
+  public io.grpc.alts.internal.Endpoint getRemoteEndpoint() {
+    return remoteEndpoint_ == null ? io.grpc.alts.internal.Endpoint.getDefaultInstance() : remoteEndpoint_;
+  }
+  /**
+   * <pre>
+   * (Optional) Endpoint information of the remote client, such as IP address,
+   * port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
+   */
+  public io.grpc.alts.internal.EndpointOrBuilder getRemoteEndpointOrBuilder() {
+    return getRemoteEndpoint();
+  }
+
+  public static final int RPC_VERSIONS_FIELD_NUMBER = 6;
+  private io.grpc.alts.internal.RpcProtocolVersions rpcVersions_;
+  /**
+   * <pre>
+   * (Optional) RPC protocol versions supported by the server.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 6;</code>
+   */
+  public boolean hasRpcVersions() {
+    return rpcVersions_ != null;
+  }
+  /**
+   * <pre>
+   * (Optional) RPC protocol versions supported by the server.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 6;</code>
+   */
+  public io.grpc.alts.internal.RpcProtocolVersions getRpcVersions() {
+    return rpcVersions_ == null ? io.grpc.alts.internal.RpcProtocolVersions.getDefaultInstance() : rpcVersions_;
+  }
+  /**
+   * <pre>
+   * (Optional) RPC protocol versions supported by the server.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 6;</code>
+   */
+  public io.grpc.alts.internal.RpcProtocolVersionsOrBuilder getRpcVersionsOrBuilder() {
+    return getRpcVersions();
+  }
+
+  private byte memoizedIsInitialized = -1;
+  public final boolean isInitialized() {
+    byte isInitialized = memoizedIsInitialized;
+    if (isInitialized == 1) return true;
+    if (isInitialized == 0) return false;
+
+    memoizedIsInitialized = 1;
+    return true;
+  }
+
+  public void writeTo(com.google.protobuf.CodedOutputStream output)
+                      throws java.io.IOException {
+    for (int i = 0; i < applicationProtocols_.size(); i++) {
+      com.google.protobuf.GeneratedMessageV3.writeString(output, 1, applicationProtocols_.getRaw(i));
+    }
+    com.google.protobuf.GeneratedMessageV3
+      .serializeIntegerMapTo(
+        output,
+        internalGetHandshakeParameters(),
+        HandshakeParametersDefaultEntryHolder.defaultEntry,
+        2);
+    if (!inBytes_.isEmpty()) {
+      output.writeBytes(3, inBytes_);
+    }
+    if (localEndpoint_ != null) {
+      output.writeMessage(4, getLocalEndpoint());
+    }
+    if (remoteEndpoint_ != null) {
+      output.writeMessage(5, getRemoteEndpoint());
+    }
+    if (rpcVersions_ != null) {
+      output.writeMessage(6, getRpcVersions());
+    }
+    unknownFields.writeTo(output);
+  }
+
+  public int getSerializedSize() {
+    int size = memoizedSize;
+    if (size != -1) return size;
+
+    size = 0;
+    {
+      int dataSize = 0;
+      for (int i = 0; i < applicationProtocols_.size(); i++) {
+        dataSize += computeStringSizeNoTag(applicationProtocols_.getRaw(i));
+      }
+      size += dataSize;
+      size += 1 * getApplicationProtocolsList().size();
+    }
+    for (java.util.Map.Entry<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters> entry
+         : internalGetHandshakeParameters().getMap().entrySet()) {
+      com.google.protobuf.MapEntry<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters>
+      handshakeParameters__ = HandshakeParametersDefaultEntryHolder.defaultEntry.newBuilderForType()
+          .setKey(entry.getKey())
+          .setValue(entry.getValue())
+          .build();
+      size += com.google.protobuf.CodedOutputStream
+          .computeMessageSize(2, handshakeParameters__);
+    }
+    if (!inBytes_.isEmpty()) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeBytesSize(3, inBytes_);
+    }
+    if (localEndpoint_ != null) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeMessageSize(4, getLocalEndpoint());
+    }
+    if (remoteEndpoint_ != null) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeMessageSize(5, getRemoteEndpoint());
+    }
+    if (rpcVersions_ != null) {
+      size += com.google.protobuf.CodedOutputStream
+        .computeMessageSize(6, getRpcVersions());
+    }
+    size += unknownFields.getSerializedSize();
+    memoizedSize = size;
+    return size;
+  }
+
+  @java.lang.Override
+  public boolean equals(final java.lang.Object obj) {
+    if (obj == this) {
+     return true;
+    }
+    if (!(obj instanceof io.grpc.alts.internal.StartServerHandshakeReq)) {
+      return super.equals(obj);
+    }
+    io.grpc.alts.internal.StartServerHandshakeReq other = (io.grpc.alts.internal.StartServerHandshakeReq) obj;
+
+    boolean result = true;
+    result = result && getApplicationProtocolsList()
+        .equals(other.getApplicationProtocolsList());
+    result = result && internalGetHandshakeParameters().equals(
+        other.internalGetHandshakeParameters());
+    result = result && getInBytes()
+        .equals(other.getInBytes());
+    result = result && (hasLocalEndpoint() == other.hasLocalEndpoint());
+    if (hasLocalEndpoint()) {
+      result = result && getLocalEndpoint()
+          .equals(other.getLocalEndpoint());
+    }
+    result = result && (hasRemoteEndpoint() == other.hasRemoteEndpoint());
+    if (hasRemoteEndpoint()) {
+      result = result && getRemoteEndpoint()
+          .equals(other.getRemoteEndpoint());
+    }
+    result = result && (hasRpcVersions() == other.hasRpcVersions());
+    if (hasRpcVersions()) {
+      result = result && getRpcVersions()
+          .equals(other.getRpcVersions());
+    }
+    result = result && unknownFields.equals(other.unknownFields);
+    return result;
+  }
+
+  @java.lang.Override
+  public int hashCode() {
+    if (memoizedHashCode != 0) {
+      return memoizedHashCode;
+    }
+    int hash = 41;
+    hash = (19 * hash) + getDescriptor().hashCode();
+    if (getApplicationProtocolsCount() > 0) {
+      hash = (37 * hash) + APPLICATION_PROTOCOLS_FIELD_NUMBER;
+      hash = (53 * hash) + getApplicationProtocolsList().hashCode();
+    }
+    if (!internalGetHandshakeParameters().getMap().isEmpty()) {
+      hash = (37 * hash) + HANDSHAKE_PARAMETERS_FIELD_NUMBER;
+      hash = (53 * hash) + internalGetHandshakeParameters().hashCode();
+    }
+    hash = (37 * hash) + IN_BYTES_FIELD_NUMBER;
+    hash = (53 * hash) + getInBytes().hashCode();
+    if (hasLocalEndpoint()) {
+      hash = (37 * hash) + LOCAL_ENDPOINT_FIELD_NUMBER;
+      hash = (53 * hash) + getLocalEndpoint().hashCode();
+    }
+    if (hasRemoteEndpoint()) {
+      hash = (37 * hash) + REMOTE_ENDPOINT_FIELD_NUMBER;
+      hash = (53 * hash) + getRemoteEndpoint().hashCode();
+    }
+    if (hasRpcVersions()) {
+      hash = (37 * hash) + RPC_VERSIONS_FIELD_NUMBER;
+      hash = (53 * hash) + getRpcVersions().hashCode();
+    }
+    hash = (29 * hash) + unknownFields.hashCode();
+    memoizedHashCode = hash;
+    return hash;
+  }
+
+  public static io.grpc.alts.internal.StartServerHandshakeReq parseFrom(
+      java.nio.ByteBuffer data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.StartServerHandshakeReq parseFrom(
+      java.nio.ByteBuffer data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.StartServerHandshakeReq parseFrom(
+      com.google.protobuf.ByteString data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.StartServerHandshakeReq parseFrom(
+      com.google.protobuf.ByteString data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.StartServerHandshakeReq parseFrom(byte[] data)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data);
+  }
+  public static io.grpc.alts.internal.StartServerHandshakeReq parseFrom(
+      byte[] data,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws com.google.protobuf.InvalidProtocolBufferException {
+    return PARSER.parseFrom(data, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.StartServerHandshakeReq parseFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.StartServerHandshakeReq parseFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.StartServerHandshakeReq parseDelimitedFrom(java.io.InputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.StartServerHandshakeReq parseDelimitedFrom(
+      java.io.InputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseDelimitedWithIOException(PARSER, input, extensionRegistry);
+  }
+  public static io.grpc.alts.internal.StartServerHandshakeReq parseFrom(
+      com.google.protobuf.CodedInputStream input)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input);
+  }
+  public static io.grpc.alts.internal.StartServerHandshakeReq parseFrom(
+      com.google.protobuf.CodedInputStream input,
+      com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+      throws java.io.IOException {
+    return com.google.protobuf.GeneratedMessageV3
+        .parseWithIOException(PARSER, input, extensionRegistry);
+  }
+
+  public Builder newBuilderForType() { return newBuilder(); }
+  public static Builder newBuilder() {
+    return DEFAULT_INSTANCE.toBuilder();
+  }
+  public static Builder newBuilder(io.grpc.alts.internal.StartServerHandshakeReq prototype) {
+    return DEFAULT_INSTANCE.toBuilder().mergeFrom(prototype);
+  }
+  public Builder toBuilder() {
+    return this == DEFAULT_INSTANCE
+        ? new Builder() : new Builder().mergeFrom(this);
+  }
+
+  @java.lang.Override
+  protected Builder newBuilderForType(
+      com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+    Builder builder = new Builder(parent);
+    return builder;
+  }
+  /**
+   * Protobuf type {@code grpc.gcp.StartServerHandshakeReq}
+   */
+  public static final class Builder extends
+      com.google.protobuf.GeneratedMessageV3.Builder<Builder> implements
+      // @@protoc_insertion_point(builder_implements:grpc.gcp.StartServerHandshakeReq)
+      io.grpc.alts.internal.StartServerHandshakeReqOrBuilder {
+    public static final com.google.protobuf.Descriptors.Descriptor
+        getDescriptor() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_StartServerHandshakeReq_descriptor;
+    }
+
+    @SuppressWarnings({"rawtypes"})
+    protected com.google.protobuf.MapField internalGetMapField(
+        int number) {
+      switch (number) {
+        case 2:
+          return internalGetHandshakeParameters();
+        default:
+          throw new RuntimeException(
+              "Invalid map field number: " + number);
+      }
+    }
+    @SuppressWarnings({"rawtypes"})
+    protected com.google.protobuf.MapField internalGetMutableMapField(
+        int number) {
+      switch (number) {
+        case 2:
+          return internalGetMutableHandshakeParameters();
+        default:
+          throw new RuntimeException(
+              "Invalid map field number: " + number);
+      }
+    }
+    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+        internalGetFieldAccessorTable() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_StartServerHandshakeReq_fieldAccessorTable
+          .ensureFieldAccessorsInitialized(
+              io.grpc.alts.internal.StartServerHandshakeReq.class, io.grpc.alts.internal.StartServerHandshakeReq.Builder.class);
+    }
+
+    // Construct using io.grpc.alts.internal.StartServerHandshakeReq.newBuilder()
+    private Builder() {
+      maybeForceBuilderInitialization();
+    }
+
+    private Builder(
+        com.google.protobuf.GeneratedMessageV3.BuilderParent parent) {
+      super(parent);
+      maybeForceBuilderInitialization();
+    }
+    private void maybeForceBuilderInitialization() {
+      if (com.google.protobuf.GeneratedMessageV3
+              .alwaysUseFieldBuilders) {
+      }
+    }
+    public Builder clear() {
+      super.clear();
+      applicationProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
+      bitField0_ = (bitField0_ & ~0x00000001);
+      internalGetMutableHandshakeParameters().clear();
+      inBytes_ = com.google.protobuf.ByteString.EMPTY;
+
+      if (localEndpointBuilder_ == null) {
+        localEndpoint_ = null;
+      } else {
+        localEndpoint_ = null;
+        localEndpointBuilder_ = null;
+      }
+      if (remoteEndpointBuilder_ == null) {
+        remoteEndpoint_ = null;
+      } else {
+        remoteEndpoint_ = null;
+        remoteEndpointBuilder_ = null;
+      }
+      if (rpcVersionsBuilder_ == null) {
+        rpcVersions_ = null;
+      } else {
+        rpcVersions_ = null;
+        rpcVersionsBuilder_ = null;
+      }
+      return this;
+    }
+
+    public com.google.protobuf.Descriptors.Descriptor
+        getDescriptorForType() {
+      return io.grpc.alts.internal.HandshakerProto.internal_static_grpc_gcp_StartServerHandshakeReq_descriptor;
+    }
+
+    public io.grpc.alts.internal.StartServerHandshakeReq getDefaultInstanceForType() {
+      return io.grpc.alts.internal.StartServerHandshakeReq.getDefaultInstance();
+    }
+
+    public io.grpc.alts.internal.StartServerHandshakeReq build() {
+      io.grpc.alts.internal.StartServerHandshakeReq result = buildPartial();
+      if (!result.isInitialized()) {
+        throw newUninitializedMessageException(result);
+      }
+      return result;
+    }
+
+    public io.grpc.alts.internal.StartServerHandshakeReq buildPartial() {
+      io.grpc.alts.internal.StartServerHandshakeReq result = new io.grpc.alts.internal.StartServerHandshakeReq(this);
+      int from_bitField0_ = bitField0_;
+      int to_bitField0_ = 0;
+      if (((bitField0_ & 0x00000001) == 0x00000001)) {
+        applicationProtocols_ = applicationProtocols_.getUnmodifiableView();
+        bitField0_ = (bitField0_ & ~0x00000001);
+      }
+      result.applicationProtocols_ = applicationProtocols_;
+      result.handshakeParameters_ = internalGetHandshakeParameters();
+      result.handshakeParameters_.makeImmutable();
+      result.inBytes_ = inBytes_;
+      if (localEndpointBuilder_ == null) {
+        result.localEndpoint_ = localEndpoint_;
+      } else {
+        result.localEndpoint_ = localEndpointBuilder_.build();
+      }
+      if (remoteEndpointBuilder_ == null) {
+        result.remoteEndpoint_ = remoteEndpoint_;
+      } else {
+        result.remoteEndpoint_ = remoteEndpointBuilder_.build();
+      }
+      if (rpcVersionsBuilder_ == null) {
+        result.rpcVersions_ = rpcVersions_;
+      } else {
+        result.rpcVersions_ = rpcVersionsBuilder_.build();
+      }
+      result.bitField0_ = to_bitField0_;
+      onBuilt();
+      return result;
+    }
+
+    public Builder clone() {
+      return (Builder) super.clone();
+    }
+    public Builder setField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.setField(field, value);
+    }
+    public Builder clearField(
+        com.google.protobuf.Descriptors.FieldDescriptor field) {
+      return (Builder) super.clearField(field);
+    }
+    public Builder clearOneof(
+        com.google.protobuf.Descriptors.OneofDescriptor oneof) {
+      return (Builder) super.clearOneof(oneof);
+    }
+    public Builder setRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        int index, java.lang.Object value) {
+      return (Builder) super.setRepeatedField(field, index, value);
+    }
+    public Builder addRepeatedField(
+        com.google.protobuf.Descriptors.FieldDescriptor field,
+        java.lang.Object value) {
+      return (Builder) super.addRepeatedField(field, value);
+    }
+    public Builder mergeFrom(com.google.protobuf.Message other) {
+      if (other instanceof io.grpc.alts.internal.StartServerHandshakeReq) {
+        return mergeFrom((io.grpc.alts.internal.StartServerHandshakeReq)other);
+      } else {
+        super.mergeFrom(other);
+        return this;
+      }
+    }
+
+    public Builder mergeFrom(io.grpc.alts.internal.StartServerHandshakeReq other) {
+      if (other == io.grpc.alts.internal.StartServerHandshakeReq.getDefaultInstance()) return this;
+      if (!other.applicationProtocols_.isEmpty()) {
+        if (applicationProtocols_.isEmpty()) {
+          applicationProtocols_ = other.applicationProtocols_;
+          bitField0_ = (bitField0_ & ~0x00000001);
+        } else {
+          ensureApplicationProtocolsIsMutable();
+          applicationProtocols_.addAll(other.applicationProtocols_);
+        }
+        onChanged();
+      }
+      internalGetMutableHandshakeParameters().mergeFrom(
+          other.internalGetHandshakeParameters());
+      if (other.getInBytes() != com.google.protobuf.ByteString.EMPTY) {
+        setInBytes(other.getInBytes());
+      }
+      if (other.hasLocalEndpoint()) {
+        mergeLocalEndpoint(other.getLocalEndpoint());
+      }
+      if (other.hasRemoteEndpoint()) {
+        mergeRemoteEndpoint(other.getRemoteEndpoint());
+      }
+      if (other.hasRpcVersions()) {
+        mergeRpcVersions(other.getRpcVersions());
+      }
+      this.mergeUnknownFields(other.unknownFields);
+      onChanged();
+      return this;
+    }
+
+    public final boolean isInitialized() {
+      return true;
+    }
+
+    public Builder mergeFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws java.io.IOException {
+      io.grpc.alts.internal.StartServerHandshakeReq parsedMessage = null;
+      try {
+        parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);
+      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+        parsedMessage = (io.grpc.alts.internal.StartServerHandshakeReq) e.getUnfinishedMessage();
+        throw e.unwrapIOException();
+      } finally {
+        if (parsedMessage != null) {
+          mergeFrom(parsedMessage);
+        }
+      }
+      return this;
+    }
+    private int bitField0_;
+
+    private com.google.protobuf.LazyStringList applicationProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
+    private void ensureApplicationProtocolsIsMutable() {
+      if (!((bitField0_ & 0x00000001) == 0x00000001)) {
+        applicationProtocols_ = new com.google.protobuf.LazyStringArrayList(applicationProtocols_);
+        bitField0_ |= 0x00000001;
+       }
+    }
+    /**
+     * <pre>
+     * The application protocols supported by the server, e.g., "h2" (for http2),
+     * "grpc".
+     * </pre>
+     *
+     * <code>repeated string application_protocols = 1;</code>
+     */
+    public com.google.protobuf.ProtocolStringList
+        getApplicationProtocolsList() {
+      return applicationProtocols_.getUnmodifiableView();
+    }
+    /**
+     * <pre>
+     * The application protocols supported by the server, e.g., "h2" (for http2),
+     * "grpc".
+     * </pre>
+     *
+     * <code>repeated string application_protocols = 1;</code>
+     */
+    public int getApplicationProtocolsCount() {
+      return applicationProtocols_.size();
+    }
+    /**
+     * <pre>
+     * The application protocols supported by the server, e.g., "h2" (for http2),
+     * "grpc".
+     * </pre>
+     *
+     * <code>repeated string application_protocols = 1;</code>
+     */
+    public java.lang.String getApplicationProtocols(int index) {
+      return applicationProtocols_.get(index);
+    }
+    /**
+     * <pre>
+     * The application protocols supported by the server, e.g., "h2" (for http2),
+     * "grpc".
+     * </pre>
+     *
+     * <code>repeated string application_protocols = 1;</code>
+     */
+    public com.google.protobuf.ByteString
+        getApplicationProtocolsBytes(int index) {
+      return applicationProtocols_.getByteString(index);
+    }
+    /**
+     * <pre>
+     * The application protocols supported by the server, e.g., "h2" (for http2),
+     * "grpc".
+     * </pre>
+     *
+     * <code>repeated string application_protocols = 1;</code>
+     */
+    public Builder setApplicationProtocols(
+        int index, java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  ensureApplicationProtocolsIsMutable();
+      applicationProtocols_.set(index, value);
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The application protocols supported by the server, e.g., "h2" (for http2),
+     * "grpc".
+     * </pre>
+     *
+     * <code>repeated string application_protocols = 1;</code>
+     */
+    public Builder addApplicationProtocols(
+        java.lang.String value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  ensureApplicationProtocolsIsMutable();
+      applicationProtocols_.add(value);
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The application protocols supported by the server, e.g., "h2" (for http2),
+     * "grpc".
+     * </pre>
+     *
+     * <code>repeated string application_protocols = 1;</code>
+     */
+    public Builder addAllApplicationProtocols(
+        java.lang.Iterable<java.lang.String> values) {
+      ensureApplicationProtocolsIsMutable();
+      com.google.protobuf.AbstractMessageLite.Builder.addAll(
+          values, applicationProtocols_);
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The application protocols supported by the server, e.g., "h2" (for http2),
+     * "grpc".
+     * </pre>
+     *
+     * <code>repeated string application_protocols = 1;</code>
+     */
+    public Builder clearApplicationProtocols() {
+      applicationProtocols_ = com.google.protobuf.LazyStringArrayList.EMPTY;
+      bitField0_ = (bitField0_ & ~0x00000001);
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * The application protocols supported by the server, e.g., "h2" (for http2),
+     * "grpc".
+     * </pre>
+     *
+     * <code>repeated string application_protocols = 1;</code>
+     */
+    public Builder addApplicationProtocolsBytes(
+        com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  checkByteStringIsUtf8(value);
+      ensureApplicationProtocolsIsMutable();
+      applicationProtocols_.add(value);
+      onChanged();
+      return this;
+    }
+
+    private com.google.protobuf.MapField<
+        java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters> handshakeParameters_;
+    private com.google.protobuf.MapField<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters>
+    internalGetHandshakeParameters() {
+      if (handshakeParameters_ == null) {
+        return com.google.protobuf.MapField.emptyMapField(
+            HandshakeParametersDefaultEntryHolder.defaultEntry);
+      }
+      return handshakeParameters_;
+    }
+    private com.google.protobuf.MapField<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters>
+    internalGetMutableHandshakeParameters() {
+      onChanged();;
+      if (handshakeParameters_ == null) {
+        handshakeParameters_ = com.google.protobuf.MapField.newMapField(
+            HandshakeParametersDefaultEntryHolder.defaultEntry);
+      }
+      if (!handshakeParameters_.isMutable()) {
+        handshakeParameters_ = handshakeParameters_.copy();
+      }
+      return handshakeParameters_;
+    }
+
+    public int getHandshakeParametersCount() {
+      return internalGetHandshakeParameters().getMap().size();
+    }
+    /**
+     * <pre>
+     * Handshake parameters (record protocols and local identities supported by
+     * the server) mapped by the handshake protocol. Each handshake security
+     * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
+     * identities. Since protobuf does not support enum as key to the map, the key
+     * to handshake_parameters is the integer value of HandshakeProtocol enum.
+     * </pre>
+     *
+     * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
+     */
+
+    public boolean containsHandshakeParameters(
+        int key) {
+      
+      return internalGetHandshakeParameters().getMap().containsKey(key);
+    }
+    /**
+     * Use {@link #getHandshakeParametersMap()} instead.
+     */
+    @java.lang.Deprecated
+    public java.util.Map<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters> getHandshakeParameters() {
+      return getHandshakeParametersMap();
+    }
+    /**
+     * <pre>
+     * Handshake parameters (record protocols and local identities supported by
+     * the server) mapped by the handshake protocol. Each handshake security
+     * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
+     * identities. Since protobuf does not support enum as key to the map, the key
+     * to handshake_parameters is the integer value of HandshakeProtocol enum.
+     * </pre>
+     *
+     * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
+     */
+
+    public java.util.Map<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters> getHandshakeParametersMap() {
+      return internalGetHandshakeParameters().getMap();
+    }
+    /**
+     * <pre>
+     * Handshake parameters (record protocols and local identities supported by
+     * the server) mapped by the handshake protocol. Each handshake security
+     * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
+     * identities. Since protobuf does not support enum as key to the map, the key
+     * to handshake_parameters is the integer value of HandshakeProtocol enum.
+     * </pre>
+     *
+     * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
+     */
+
+    public io.grpc.alts.internal.ServerHandshakeParameters getHandshakeParametersOrDefault(
+        int key,
+        io.grpc.alts.internal.ServerHandshakeParameters defaultValue) {
+      
+      java.util.Map<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters> map =
+          internalGetHandshakeParameters().getMap();
+      return map.containsKey(key) ? map.get(key) : defaultValue;
+    }
+    /**
+     * <pre>
+     * Handshake parameters (record protocols and local identities supported by
+     * the server) mapped by the handshake protocol. Each handshake security
+     * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
+     * identities. Since protobuf does not support enum as key to the map, the key
+     * to handshake_parameters is the integer value of HandshakeProtocol enum.
+     * </pre>
+     *
+     * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
+     */
+
+    public io.grpc.alts.internal.ServerHandshakeParameters getHandshakeParametersOrThrow(
+        int key) {
+      
+      java.util.Map<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters> map =
+          internalGetHandshakeParameters().getMap();
+      if (!map.containsKey(key)) {
+        throw new java.lang.IllegalArgumentException();
+      }
+      return map.get(key);
+    }
+
+    public Builder clearHandshakeParameters() {
+      internalGetMutableHandshakeParameters().getMutableMap()
+          .clear();
+      return this;
+    }
+    /**
+     * <pre>
+     * Handshake parameters (record protocols and local identities supported by
+     * the server) mapped by the handshake protocol. Each handshake security
+     * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
+     * identities. Since protobuf does not support enum as key to the map, the key
+     * to handshake_parameters is the integer value of HandshakeProtocol enum.
+     * </pre>
+     *
+     * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
+     */
+
+    public Builder removeHandshakeParameters(
+        int key) {
+      
+      internalGetMutableHandshakeParameters().getMutableMap()
+          .remove(key);
+      return this;
+    }
+    /**
+     * Use alternate mutation accessors instead.
+     */
+    @java.lang.Deprecated
+    public java.util.Map<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters>
+    getMutableHandshakeParameters() {
+      return internalGetMutableHandshakeParameters().getMutableMap();
+    }
+    /**
+     * <pre>
+     * Handshake parameters (record protocols and local identities supported by
+     * the server) mapped by the handshake protocol. Each handshake security
+     * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
+     * identities. Since protobuf does not support enum as key to the map, the key
+     * to handshake_parameters is the integer value of HandshakeProtocol enum.
+     * </pre>
+     *
+     * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
+     */
+    public Builder putHandshakeParameters(
+        int key,
+        io.grpc.alts.internal.ServerHandshakeParameters value) {
+      
+      if (value == null) { throw new java.lang.NullPointerException(); }
+      internalGetMutableHandshakeParameters().getMutableMap()
+          .put(key, value);
+      return this;
+    }
+    /**
+     * <pre>
+     * Handshake parameters (record protocols and local identities supported by
+     * the server) mapped by the handshake protocol. Each handshake security
+     * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
+     * identities. Since protobuf does not support enum as key to the map, the key
+     * to handshake_parameters is the integer value of HandshakeProtocol enum.
+     * </pre>
+     *
+     * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
+     */
+
+    public Builder putAllHandshakeParameters(
+        java.util.Map<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters> values) {
+      internalGetMutableHandshakeParameters().getMutableMap()
+          .putAll(values);
+      return this;
+    }
+
+    private com.google.protobuf.ByteString inBytes_ = com.google.protobuf.ByteString.EMPTY;
+    /**
+     * <pre>
+     * Bytes in out_frames returned from the peer's HandshakerResp. It is possible
+     * that the peer's out_frames are split into multiple HandshakReq messages.
+     * </pre>
+     *
+     * <code>bytes in_bytes = 3;</code>
+     */
+    public com.google.protobuf.ByteString getInBytes() {
+      return inBytes_;
+    }
+    /**
+     * <pre>
+     * Bytes in out_frames returned from the peer's HandshakerResp. It is possible
+     * that the peer's out_frames are split into multiple HandshakReq messages.
+     * </pre>
+     *
+     * <code>bytes in_bytes = 3;</code>
+     */
+    public Builder setInBytes(com.google.protobuf.ByteString value) {
+      if (value == null) {
+    throw new NullPointerException();
+  }
+  
+      inBytes_ = value;
+      onChanged();
+      return this;
+    }
+    /**
+     * <pre>
+     * Bytes in out_frames returned from the peer's HandshakerResp. It is possible
+     * that the peer's out_frames are split into multiple HandshakReq messages.
+     * </pre>
+     *
+     * <code>bytes in_bytes = 3;</code>
+     */
+    public Builder clearInBytes() {
+      
+      inBytes_ = getDefaultInstance().getInBytes();
+      onChanged();
+      return this;
+    }
+
+    private io.grpc.alts.internal.Endpoint localEndpoint_ = null;
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.Endpoint, io.grpc.alts.internal.Endpoint.Builder, io.grpc.alts.internal.EndpointOrBuilder> localEndpointBuilder_;
+    /**
+     * <pre>
+     * (Optional) Local endpoint information of the connection to the client,
+     * such as local IP address, port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
+     */
+    public boolean hasLocalEndpoint() {
+      return localEndpointBuilder_ != null || localEndpoint_ != null;
+    }
+    /**
+     * <pre>
+     * (Optional) Local endpoint information of the connection to the client,
+     * such as local IP address, port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
+     */
+    public io.grpc.alts.internal.Endpoint getLocalEndpoint() {
+      if (localEndpointBuilder_ == null) {
+        return localEndpoint_ == null ? io.grpc.alts.internal.Endpoint.getDefaultInstance() : localEndpoint_;
+      } else {
+        return localEndpointBuilder_.getMessage();
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) Local endpoint information of the connection to the client,
+     * such as local IP address, port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
+     */
+    public Builder setLocalEndpoint(io.grpc.alts.internal.Endpoint value) {
+      if (localEndpointBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        localEndpoint_ = value;
+        onChanged();
+      } else {
+        localEndpointBuilder_.setMessage(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Local endpoint information of the connection to the client,
+     * such as local IP address, port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
+     */
+    public Builder setLocalEndpoint(
+        io.grpc.alts.internal.Endpoint.Builder builderForValue) {
+      if (localEndpointBuilder_ == null) {
+        localEndpoint_ = builderForValue.build();
+        onChanged();
+      } else {
+        localEndpointBuilder_.setMessage(builderForValue.build());
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Local endpoint information of the connection to the client,
+     * such as local IP address, port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
+     */
+    public Builder mergeLocalEndpoint(io.grpc.alts.internal.Endpoint value) {
+      if (localEndpointBuilder_ == null) {
+        if (localEndpoint_ != null) {
+          localEndpoint_ =
+            io.grpc.alts.internal.Endpoint.newBuilder(localEndpoint_).mergeFrom(value).buildPartial();
+        } else {
+          localEndpoint_ = value;
+        }
+        onChanged();
+      } else {
+        localEndpointBuilder_.mergeFrom(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Local endpoint information of the connection to the client,
+     * such as local IP address, port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
+     */
+    public Builder clearLocalEndpoint() {
+      if (localEndpointBuilder_ == null) {
+        localEndpoint_ = null;
+        onChanged();
+      } else {
+        localEndpoint_ = null;
+        localEndpointBuilder_ = null;
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Local endpoint information of the connection to the client,
+     * such as local IP address, port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
+     */
+    public io.grpc.alts.internal.Endpoint.Builder getLocalEndpointBuilder() {
+      
+      onChanged();
+      return getLocalEndpointFieldBuilder().getBuilder();
+    }
+    /**
+     * <pre>
+     * (Optional) Local endpoint information of the connection to the client,
+     * such as local IP address, port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
+     */
+    public io.grpc.alts.internal.EndpointOrBuilder getLocalEndpointOrBuilder() {
+      if (localEndpointBuilder_ != null) {
+        return localEndpointBuilder_.getMessageOrBuilder();
+      } else {
+        return localEndpoint_ == null ?
+            io.grpc.alts.internal.Endpoint.getDefaultInstance() : localEndpoint_;
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) Local endpoint information of the connection to the client,
+     * such as local IP address, port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
+     */
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.Endpoint, io.grpc.alts.internal.Endpoint.Builder, io.grpc.alts.internal.EndpointOrBuilder> 
+        getLocalEndpointFieldBuilder() {
+      if (localEndpointBuilder_ == null) {
+        localEndpointBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
+            io.grpc.alts.internal.Endpoint, io.grpc.alts.internal.Endpoint.Builder, io.grpc.alts.internal.EndpointOrBuilder>(
+                getLocalEndpoint(),
+                getParentForChildren(),
+                isClean());
+        localEndpoint_ = null;
+      }
+      return localEndpointBuilder_;
+    }
+
+    private io.grpc.alts.internal.Endpoint remoteEndpoint_ = null;
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.Endpoint, io.grpc.alts.internal.Endpoint.Builder, io.grpc.alts.internal.EndpointOrBuilder> remoteEndpointBuilder_;
+    /**
+     * <pre>
+     * (Optional) Endpoint information of the remote client, such as IP address,
+     * port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
+     */
+    public boolean hasRemoteEndpoint() {
+      return remoteEndpointBuilder_ != null || remoteEndpoint_ != null;
+    }
+    /**
+     * <pre>
+     * (Optional) Endpoint information of the remote client, such as IP address,
+     * port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
+     */
+    public io.grpc.alts.internal.Endpoint getRemoteEndpoint() {
+      if (remoteEndpointBuilder_ == null) {
+        return remoteEndpoint_ == null ? io.grpc.alts.internal.Endpoint.getDefaultInstance() : remoteEndpoint_;
+      } else {
+        return remoteEndpointBuilder_.getMessage();
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) Endpoint information of the remote client, such as IP address,
+     * port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
+     */
+    public Builder setRemoteEndpoint(io.grpc.alts.internal.Endpoint value) {
+      if (remoteEndpointBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        remoteEndpoint_ = value;
+        onChanged();
+      } else {
+        remoteEndpointBuilder_.setMessage(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Endpoint information of the remote client, such as IP address,
+     * port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
+     */
+    public Builder setRemoteEndpoint(
+        io.grpc.alts.internal.Endpoint.Builder builderForValue) {
+      if (remoteEndpointBuilder_ == null) {
+        remoteEndpoint_ = builderForValue.build();
+        onChanged();
+      } else {
+        remoteEndpointBuilder_.setMessage(builderForValue.build());
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Endpoint information of the remote client, such as IP address,
+     * port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
+     */
+    public Builder mergeRemoteEndpoint(io.grpc.alts.internal.Endpoint value) {
+      if (remoteEndpointBuilder_ == null) {
+        if (remoteEndpoint_ != null) {
+          remoteEndpoint_ =
+            io.grpc.alts.internal.Endpoint.newBuilder(remoteEndpoint_).mergeFrom(value).buildPartial();
+        } else {
+          remoteEndpoint_ = value;
+        }
+        onChanged();
+      } else {
+        remoteEndpointBuilder_.mergeFrom(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Endpoint information of the remote client, such as IP address,
+     * port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
+     */
+    public Builder clearRemoteEndpoint() {
+      if (remoteEndpointBuilder_ == null) {
+        remoteEndpoint_ = null;
+        onChanged();
+      } else {
+        remoteEndpoint_ = null;
+        remoteEndpointBuilder_ = null;
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) Endpoint information of the remote client, such as IP address,
+     * port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
+     */
+    public io.grpc.alts.internal.Endpoint.Builder getRemoteEndpointBuilder() {
+      
+      onChanged();
+      return getRemoteEndpointFieldBuilder().getBuilder();
+    }
+    /**
+     * <pre>
+     * (Optional) Endpoint information of the remote client, such as IP address,
+     * port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
+     */
+    public io.grpc.alts.internal.EndpointOrBuilder getRemoteEndpointOrBuilder() {
+      if (remoteEndpointBuilder_ != null) {
+        return remoteEndpointBuilder_.getMessageOrBuilder();
+      } else {
+        return remoteEndpoint_ == null ?
+            io.grpc.alts.internal.Endpoint.getDefaultInstance() : remoteEndpoint_;
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) Endpoint information of the remote client, such as IP address,
+     * port number, and network protocol.
+     * </pre>
+     *
+     * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
+     */
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.Endpoint, io.grpc.alts.internal.Endpoint.Builder, io.grpc.alts.internal.EndpointOrBuilder> 
+        getRemoteEndpointFieldBuilder() {
+      if (remoteEndpointBuilder_ == null) {
+        remoteEndpointBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
+            io.grpc.alts.internal.Endpoint, io.grpc.alts.internal.Endpoint.Builder, io.grpc.alts.internal.EndpointOrBuilder>(
+                getRemoteEndpoint(),
+                getParentForChildren(),
+                isClean());
+        remoteEndpoint_ = null;
+      }
+      return remoteEndpointBuilder_;
+    }
+
+    private io.grpc.alts.internal.RpcProtocolVersions rpcVersions_ = null;
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.RpcProtocolVersions, io.grpc.alts.internal.RpcProtocolVersions.Builder, io.grpc.alts.internal.RpcProtocolVersionsOrBuilder> rpcVersionsBuilder_;
+    /**
+     * <pre>
+     * (Optional) RPC protocol versions supported by the server.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 6;</code>
+     */
+    public boolean hasRpcVersions() {
+      return rpcVersionsBuilder_ != null || rpcVersions_ != null;
+    }
+    /**
+     * <pre>
+     * (Optional) RPC protocol versions supported by the server.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 6;</code>
+     */
+    public io.grpc.alts.internal.RpcProtocolVersions getRpcVersions() {
+      if (rpcVersionsBuilder_ == null) {
+        return rpcVersions_ == null ? io.grpc.alts.internal.RpcProtocolVersions.getDefaultInstance() : rpcVersions_;
+      } else {
+        return rpcVersionsBuilder_.getMessage();
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) RPC protocol versions supported by the server.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 6;</code>
+     */
+    public Builder setRpcVersions(io.grpc.alts.internal.RpcProtocolVersions value) {
+      if (rpcVersionsBuilder_ == null) {
+        if (value == null) {
+          throw new NullPointerException();
+        }
+        rpcVersions_ = value;
+        onChanged();
+      } else {
+        rpcVersionsBuilder_.setMessage(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) RPC protocol versions supported by the server.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 6;</code>
+     */
+    public Builder setRpcVersions(
+        io.grpc.alts.internal.RpcProtocolVersions.Builder builderForValue) {
+      if (rpcVersionsBuilder_ == null) {
+        rpcVersions_ = builderForValue.build();
+        onChanged();
+      } else {
+        rpcVersionsBuilder_.setMessage(builderForValue.build());
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) RPC protocol versions supported by the server.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 6;</code>
+     */
+    public Builder mergeRpcVersions(io.grpc.alts.internal.RpcProtocolVersions value) {
+      if (rpcVersionsBuilder_ == null) {
+        if (rpcVersions_ != null) {
+          rpcVersions_ =
+            io.grpc.alts.internal.RpcProtocolVersions.newBuilder(rpcVersions_).mergeFrom(value).buildPartial();
+        } else {
+          rpcVersions_ = value;
+        }
+        onChanged();
+      } else {
+        rpcVersionsBuilder_.mergeFrom(value);
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) RPC protocol versions supported by the server.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 6;</code>
+     */
+    public Builder clearRpcVersions() {
+      if (rpcVersionsBuilder_ == null) {
+        rpcVersions_ = null;
+        onChanged();
+      } else {
+        rpcVersions_ = null;
+        rpcVersionsBuilder_ = null;
+      }
+
+      return this;
+    }
+    /**
+     * <pre>
+     * (Optional) RPC protocol versions supported by the server.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 6;</code>
+     */
+    public io.grpc.alts.internal.RpcProtocolVersions.Builder getRpcVersionsBuilder() {
+      
+      onChanged();
+      return getRpcVersionsFieldBuilder().getBuilder();
+    }
+    /**
+     * <pre>
+     * (Optional) RPC protocol versions supported by the server.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 6;</code>
+     */
+    public io.grpc.alts.internal.RpcProtocolVersionsOrBuilder getRpcVersionsOrBuilder() {
+      if (rpcVersionsBuilder_ != null) {
+        return rpcVersionsBuilder_.getMessageOrBuilder();
+      } else {
+        return rpcVersions_ == null ?
+            io.grpc.alts.internal.RpcProtocolVersions.getDefaultInstance() : rpcVersions_;
+      }
+    }
+    /**
+     * <pre>
+     * (Optional) RPC protocol versions supported by the server.
+     * </pre>
+     *
+     * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 6;</code>
+     */
+    private com.google.protobuf.SingleFieldBuilderV3<
+        io.grpc.alts.internal.RpcProtocolVersions, io.grpc.alts.internal.RpcProtocolVersions.Builder, io.grpc.alts.internal.RpcProtocolVersionsOrBuilder> 
+        getRpcVersionsFieldBuilder() {
+      if (rpcVersionsBuilder_ == null) {
+        rpcVersionsBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
+            io.grpc.alts.internal.RpcProtocolVersions, io.grpc.alts.internal.RpcProtocolVersions.Builder, io.grpc.alts.internal.RpcProtocolVersionsOrBuilder>(
+                getRpcVersions(),
+                getParentForChildren(),
+                isClean());
+        rpcVersions_ = null;
+      }
+      return rpcVersionsBuilder_;
+    }
+    public final Builder setUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.setUnknownFieldsProto3(unknownFields);
+    }
+
+    public final Builder mergeUnknownFields(
+        final com.google.protobuf.UnknownFieldSet unknownFields) {
+      return super.mergeUnknownFields(unknownFields);
+    }
+
+
+    // @@protoc_insertion_point(builder_scope:grpc.gcp.StartServerHandshakeReq)
+  }
+
+  // @@protoc_insertion_point(class_scope:grpc.gcp.StartServerHandshakeReq)
+  private static final io.grpc.alts.internal.StartServerHandshakeReq DEFAULT_INSTANCE;
+  static {
+    DEFAULT_INSTANCE = new io.grpc.alts.internal.StartServerHandshakeReq();
+  }
+
+  public static io.grpc.alts.internal.StartServerHandshakeReq getDefaultInstance() {
+    return DEFAULT_INSTANCE;
+  }
+
+  private static final com.google.protobuf.Parser<StartServerHandshakeReq>
+      PARSER = new com.google.protobuf.AbstractParser<StartServerHandshakeReq>() {
+    public StartServerHandshakeReq parsePartialFrom(
+        com.google.protobuf.CodedInputStream input,
+        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
+        throws com.google.protobuf.InvalidProtocolBufferException {
+      return new StartServerHandshakeReq(input, extensionRegistry);
+    }
+  };
+
+  public static com.google.protobuf.Parser<StartServerHandshakeReq> parser() {
+    return PARSER;
+  }
+
+  @java.lang.Override
+  public com.google.protobuf.Parser<StartServerHandshakeReq> getParserForType() {
+    return PARSER;
+  }
+
+  public io.grpc.alts.internal.StartServerHandshakeReq getDefaultInstanceForType() {
+    return DEFAULT_INSTANCE;
+  }
+
+}
+
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/StartServerHandshakeReqOrBuilder.java b/alts/src/generated/main/java/io/grpc/alts/internal/StartServerHandshakeReqOrBuilder.java
new file mode 100644
index 0000000000..29a607cd7e
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/StartServerHandshakeReqOrBuilder.java
@@ -0,0 +1,213 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/handshaker.proto
+
+package io.grpc.alts.internal;
+
+public interface StartServerHandshakeReqOrBuilder extends
+    // @@protoc_insertion_point(interface_extends:grpc.gcp.StartServerHandshakeReq)
+    com.google.protobuf.MessageOrBuilder {
+
+  /**
+   * <pre>
+   * The application protocols supported by the server, e.g., "h2" (for http2),
+   * "grpc".
+   * </pre>
+   *
+   * <code>repeated string application_protocols = 1;</code>
+   */
+  java.util.List<java.lang.String>
+      getApplicationProtocolsList();
+  /**
+   * <pre>
+   * The application protocols supported by the server, e.g., "h2" (for http2),
+   * "grpc".
+   * </pre>
+   *
+   * <code>repeated string application_protocols = 1;</code>
+   */
+  int getApplicationProtocolsCount();
+  /**
+   * <pre>
+   * The application protocols supported by the server, e.g., "h2" (for http2),
+   * "grpc".
+   * </pre>
+   *
+   * <code>repeated string application_protocols = 1;</code>
+   */
+  java.lang.String getApplicationProtocols(int index);
+  /**
+   * <pre>
+   * The application protocols supported by the server, e.g., "h2" (for http2),
+   * "grpc".
+   * </pre>
+   *
+   * <code>repeated string application_protocols = 1;</code>
+   */
+  com.google.protobuf.ByteString
+      getApplicationProtocolsBytes(int index);
+
+  /**
+   * <pre>
+   * Handshake parameters (record protocols and local identities supported by
+   * the server) mapped by the handshake protocol. Each handshake security
+   * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
+   * identities. Since protobuf does not support enum as key to the map, the key
+   * to handshake_parameters is the integer value of HandshakeProtocol enum.
+   * </pre>
+   *
+   * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
+   */
+  int getHandshakeParametersCount();
+  /**
+   * <pre>
+   * Handshake parameters (record protocols and local identities supported by
+   * the server) mapped by the handshake protocol. Each handshake security
+   * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
+   * identities. Since protobuf does not support enum as key to the map, the key
+   * to handshake_parameters is the integer value of HandshakeProtocol enum.
+   * </pre>
+   *
+   * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
+   */
+  boolean containsHandshakeParameters(
+      int key);
+  /**
+   * Use {@link #getHandshakeParametersMap()} instead.
+   */
+  @java.lang.Deprecated
+  java.util.Map<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters>
+  getHandshakeParameters();
+  /**
+   * <pre>
+   * Handshake parameters (record protocols and local identities supported by
+   * the server) mapped by the handshake protocol. Each handshake security
+   * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
+   * identities. Since protobuf does not support enum as key to the map, the key
+   * to handshake_parameters is the integer value of HandshakeProtocol enum.
+   * </pre>
+   *
+   * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
+   */
+  java.util.Map<java.lang.Integer, io.grpc.alts.internal.ServerHandshakeParameters>
+  getHandshakeParametersMap();
+  /**
+   * <pre>
+   * Handshake parameters (record protocols and local identities supported by
+   * the server) mapped by the handshake protocol. Each handshake security
+   * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
+   * identities. Since protobuf does not support enum as key to the map, the key
+   * to handshake_parameters is the integer value of HandshakeProtocol enum.
+   * </pre>
+   *
+   * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
+   */
+
+  io.grpc.alts.internal.ServerHandshakeParameters getHandshakeParametersOrDefault(
+      int key,
+      io.grpc.alts.internal.ServerHandshakeParameters defaultValue);
+  /**
+   * <pre>
+   * Handshake parameters (record protocols and local identities supported by
+   * the server) mapped by the handshake protocol. Each handshake security
+   * protocol (e.g., TLS or ALTS) has its own set of record protocols and local
+   * identities. Since protobuf does not support enum as key to the map, the key
+   * to handshake_parameters is the integer value of HandshakeProtocol enum.
+   * </pre>
+   *
+   * <code>map&lt;int32, .grpc.gcp.ServerHandshakeParameters&gt; handshake_parameters = 2;</code>
+   */
+
+  io.grpc.alts.internal.ServerHandshakeParameters getHandshakeParametersOrThrow(
+      int key);
+
+  /**
+   * <pre>
+   * Bytes in out_frames returned from the peer's HandshakerResp. It is possible
+   * that the peer's out_frames are split into multiple HandshakReq messages.
+   * </pre>
+   *
+   * <code>bytes in_bytes = 3;</code>
+   */
+  com.google.protobuf.ByteString getInBytes();
+
+  /**
+   * <pre>
+   * (Optional) Local endpoint information of the connection to the client,
+   * such as local IP address, port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
+   */
+  boolean hasLocalEndpoint();
+  /**
+   * <pre>
+   * (Optional) Local endpoint information of the connection to the client,
+   * such as local IP address, port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
+   */
+  io.grpc.alts.internal.Endpoint getLocalEndpoint();
+  /**
+   * <pre>
+   * (Optional) Local endpoint information of the connection to the client,
+   * such as local IP address, port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint local_endpoint = 4;</code>
+   */
+  io.grpc.alts.internal.EndpointOrBuilder getLocalEndpointOrBuilder();
+
+  /**
+   * <pre>
+   * (Optional) Endpoint information of the remote client, such as IP address,
+   * port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
+   */
+  boolean hasRemoteEndpoint();
+  /**
+   * <pre>
+   * (Optional) Endpoint information of the remote client, such as IP address,
+   * port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
+   */
+  io.grpc.alts.internal.Endpoint getRemoteEndpoint();
+  /**
+   * <pre>
+   * (Optional) Endpoint information of the remote client, such as IP address,
+   * port number, and network protocol.
+   * </pre>
+   *
+   * <code>.grpc.gcp.Endpoint remote_endpoint = 5;</code>
+   */
+  io.grpc.alts.internal.EndpointOrBuilder getRemoteEndpointOrBuilder();
+
+  /**
+   * <pre>
+   * (Optional) RPC protocol versions supported by the server.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 6;</code>
+   */
+  boolean hasRpcVersions();
+  /**
+   * <pre>
+   * (Optional) RPC protocol versions supported by the server.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 6;</code>
+   */
+  io.grpc.alts.internal.RpcProtocolVersions getRpcVersions();
+  /**
+   * <pre>
+   * (Optional) RPC protocol versions supported by the server.
+   * </pre>
+   *
+   * <code>.grpc.gcp.RpcProtocolVersions rpc_versions = 6;</code>
+   */
+  io.grpc.alts.internal.RpcProtocolVersionsOrBuilder getRpcVersionsOrBuilder();
+}
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/TransportSecurityCommon.java b/alts/src/generated/main/java/io/grpc/alts/internal/TransportSecurityCommon.java
deleted file mode 100644
index beb3839837..0000000000
--- a/alts/src/generated/main/java/io/grpc/alts/internal/TransportSecurityCommon.java
+++ /dev/null
@@ -1,1612 +0,0 @@
-// Generated by the protocol buffer compiler.  DO NOT EDIT!
-// source: grpc/gcp/transport_security_common.proto
-
-package io.grpc.alts.internal;
-
-public final class TransportSecurityCommon {
-  private TransportSecurityCommon() {}
-  public static void registerAllExtensions(
-      com.google.protobuf.ExtensionRegistryLite registry) {
-  }
-
-  public static void registerAllExtensions(
-      com.google.protobuf.ExtensionRegistry registry) {
-    registerAllExtensions(
-        (com.google.protobuf.ExtensionRegistryLite) registry);
-  }
-  /**
-   * <pre>
-   * The security level of the created channel. The list is sorted in increasing
-   * level of security. This order must always be maintained.
-   * </pre>
-   *
-   * Protobuf enum {@code grpc.gcp.SecurityLevel}
-   */
-  public enum SecurityLevel
-      implements com.google.protobuf.ProtocolMessageEnum {
-    /**
-     * <code>SECURITY_NONE = 0;</code>
-     */
-    SECURITY_NONE(0),
-    /**
-     * <code>INTEGRITY_ONLY = 1;</code>
-     */
-    INTEGRITY_ONLY(1),
-    /**
-     * <code>INTEGRITY_AND_PRIVACY = 2;</code>
-     */
-    INTEGRITY_AND_PRIVACY(2),
-    UNRECOGNIZED(-1),
-    ;
-
-    /**
-     * <code>SECURITY_NONE = 0;</code>
-     */
-    public static final int SECURITY_NONE_VALUE = 0;
-    /**
-     * <code>INTEGRITY_ONLY = 1;</code>
-     */
-    public static final int INTEGRITY_ONLY_VALUE = 1;
-    /**
-     * <code>INTEGRITY_AND_PRIVACY = 2;</code>
-     */
-    public static final int INTEGRITY_AND_PRIVACY_VALUE = 2;
-
-
-    public final int getNumber() {
-      if (this == UNRECOGNIZED) {
-        throw new java.lang.IllegalArgumentException(
-            "Can't get the number of an unknown enum value.");
-      }
-      return value;
-    }
-
-    /**
-     * @deprecated Use {@link #forNumber(int)} instead.
-     */
-    @java.lang.Deprecated
-    public static SecurityLevel valueOf(int value) {
-      return forNumber(value);
-    }
-
-    public static SecurityLevel forNumber(int value) {
-      switch (value) {
-        case 0: return SECURITY_NONE;
-        case 1: return INTEGRITY_ONLY;
-        case 2: return INTEGRITY_AND_PRIVACY;
-        default: return null;
-      }
-    }
-
-    public static com.google.protobuf.Internal.EnumLiteMap<SecurityLevel>
-        internalGetValueMap() {
-      return internalValueMap;
-    }
-    private static final com.google.protobuf.Internal.EnumLiteMap<
-        SecurityLevel> internalValueMap =
-          new com.google.protobuf.Internal.EnumLiteMap<SecurityLevel>() {
-            public SecurityLevel findValueByNumber(int number) {
-              return SecurityLevel.forNumber(number);
-            }
-          };
-
-    public final com.google.protobuf.Descriptors.EnumValueDescriptor
-        getValueDescriptor() {
-      return getDescriptor().getValues().get(ordinal());
-    }
-    public final com.google.protobuf.Descriptors.EnumDescriptor
-        getDescriptorForType() {
-      return getDescriptor();
-    }
-    public static final com.google.protobuf.Descriptors.EnumDescriptor
-        getDescriptor() {
-      return io.grpc.alts.internal.TransportSecurityCommon.getDescriptor().getEnumTypes().get(0);
-    }
-
-    private static final SecurityLevel[] VALUES = values();
-
-    public static SecurityLevel valueOf(
-        com.google.protobuf.Descriptors.EnumValueDescriptor desc) {
-      if (desc.getType() != getDescriptor()) {
-        throw new java.lang.IllegalArgumentException(
-          "EnumValueDescriptor is not for this type.");
-      }
-      if (desc.getIndex() == -1) {
-        return UNRECOGNIZED;
-      }
-      return VALUES[desc.getIndex()];
-    }
-
-    private final int value;
-
-    private SecurityLevel(int value) {
-      this.value = value;
-    }
-
-    // @@protoc_insertion_point(enum_scope:grpc.gcp.SecurityLevel)
-  }
-
-  public interface RpcProtocolVersionsOrBuilder extends
-      // @@protoc_insertion_point(interface_extends:grpc.gcp.RpcProtocolVersions)
-      com.google.protobuf.MessageOrBuilder {
-
-    /**
-     * <pre>
-     * Maximum supported RPC version.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
-     */
-    boolean hasMaxRpcVersion();
-    /**
-     * <pre>
-     * Maximum supported RPC version.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
-     */
-    io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version getMaxRpcVersion();
-    /**
-     * <pre>
-     * Maximum supported RPC version.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
-     */
-    io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.VersionOrBuilder getMaxRpcVersionOrBuilder();
-
-    /**
-     * <pre>
-     * Minimum supported RPC version.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
-     */
-    boolean hasMinRpcVersion();
-    /**
-     * <pre>
-     * Minimum supported RPC version.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
-     */
-    io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version getMinRpcVersion();
-    /**
-     * <pre>
-     * Minimum supported RPC version.
-     * </pre>
-     *
-     * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
-     */
-    io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.VersionOrBuilder getMinRpcVersionOrBuilder();
-  }
-  /**
-   * <pre>
-   * Max and min supported RPC protocol versions.
-   * </pre>
-   *
-   * Protobuf type {@code grpc.gcp.RpcProtocolVersions}
-   */
-  public  static final class RpcProtocolVersions extends
-      com.google.protobuf.GeneratedMessageV3 implements
-      // @@protoc_insertion_point(message_implements:grpc.gcp.RpcProtocolVersions)
-      RpcProtocolVersionsOrBuilder {
-  private static final long serialVersionUID = 0L;
-    // Use RpcProtocolVersions.newBuilder() to construct.
-    private RpcProtocolVersions(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
-      super(builder);
-    }
-    private RpcProtocolVersions() {
-    }
-
-    @java.lang.Override
-    public final com.google.protobuf.UnknownFieldSet
-    getUnknownFields() {
-      return this.unknownFields;
-    }
-    private RpcProtocolVersions(
-        com.google.protobuf.CodedInputStream input,
-        com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-        throws com.google.protobuf.InvalidProtocolBufferException {
-      this();
-      if (extensionRegistry == null) {
-        throw new java.lang.NullPointerException();
-      }
-      int mutable_bitField0_ = 0;
-      com.google.protobuf.UnknownFieldSet.Builder unknownFields =
-          com.google.protobuf.UnknownFieldSet.newBuilder();
-      try {
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-          int tag = input.readTag();
-          switch (tag) {
-            case 0:
-              done = true;
-              break;
-            default: {
-              if (!parseUnknownFieldProto3(
-                  input, unknownFields, extensionRegistry, tag)) {
-                done = true;
-              }
-              break;
-            }
-            case 10: {
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.Builder subBuilder = null;
-              if (maxRpcVersion_ != null) {
-                subBuilder = maxRpcVersion_.toBuilder();
-              }
-              maxRpcVersion_ = input.readMessage(io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.parser(), extensionRegistry);
-              if (subBuilder != null) {
-                subBuilder.mergeFrom(maxRpcVersion_);
-                maxRpcVersion_ = subBuilder.buildPartial();
-              }
-
-              break;
-            }
-            case 18: {
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.Builder subBuilder = null;
-              if (minRpcVersion_ != null) {
-                subBuilder = minRpcVersion_.toBuilder();
-              }
-              minRpcVersion_ = input.readMessage(io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.parser(), extensionRegistry);
-              if (subBuilder != null) {
-                subBuilder.mergeFrom(minRpcVersion_);
-                minRpcVersion_ = subBuilder.buildPartial();
-              }
-
-              break;
-            }
-          }
-        }
-      } catch (com.google.protobuf.InvalidProtocolBufferException e) {
-        throw e.setUnfinishedMessage(this);
-      } catch (java.io.IOException e) {
-        throw new com.google.protobuf.InvalidProtocolBufferException(
-            e).setUnfinishedMessage(this);
-      } finally {
-        this.unknownFields = unknownFields.build();
-        makeExtensionsImmutable();
-      }
-    }
-    public static final com.google.protobuf.Descriptors.Descriptor
-        getDescriptor() {
-      return io.grpc.alts.internal.TransportSecurityCommon.internal_static_grpc_gcp_RpcProtocolVersions_descriptor;
-    }
-
-    protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
-        internalGetFieldAccessorTable() {
-      return io.grpc.alts.internal.TransportSecurityCommon.internal_static_grpc_gcp_RpcProtocolVersions_fieldAccessorTable
-          .ensureFieldAccessorsInitialized(
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.class, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Builder.class);
-    }
-
-    public interface VersionOrBuilder extends
-        // @@protoc_insertion_point(interface_extends:grpc.gcp.RpcProtocolVersions.Version)
-        com.google.protobuf.MessageOrBuilder {
-
-      /**
-       * <code>uint32 major = 1;</code>
-       */
-      int getMajor();
-
-      /**
-       * <code>uint32 minor = 2;</code>
-       */
-      int getMinor();
-    }
-    /**
-     * <pre>
-     * RPC version contains a major version and a minor version.
-     * </pre>
-     *
-     * Protobuf type {@code grpc.gcp.RpcProtocolVersions.Version}
-     */
-    public  static final class Version extends
-        com.google.protobuf.GeneratedMessageV3 implements
-        // @@protoc_insertion_point(message_implements:grpc.gcp.RpcProtocolVersions.Version)
-        VersionOrBuilder {
-    private static final long serialVersionUID = 0L;
-      // Use Version.newBuilder() to construct.
-      private Version(com.google.protobuf.GeneratedMessageV3.Builder<?> builder) {
-        super(builder);
-      }
-      private Version() {
-        major_ = 0;
-        minor_ = 0;
-      }
-
-      @java.lang.Override
-      public final com.google.protobuf.UnknownFieldSet
-      getUnknownFields() {
-        return this.unknownFields;
-      }
-      private Version(
-          com.google.protobuf.CodedInputStream input,
-          com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-          throws com.google.protobuf.InvalidProtocolBufferException {
-        this();
-        if (extensionRegistry == null) {
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-        try {
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-              case 8: {
-
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-              case 16: {
-
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-          throw e.setUnfinishedMessage(this);
-        } catch (java.io.IOException e) {
-          throw new com.google.protobuf.InvalidProtocolBufferException(
-              e).setUnfinishedMessage(this);
-        } finally {
-          this.unknownFields = unknownFields.build();
-          makeExtensionsImmutable();
-        }
-      }
-      public static final com.google.protobuf.Descriptors.Descriptor
-          getDescriptor() {
-        return io.grpc.alts.internal.TransportSecurityCommon.internal_static_grpc_gcp_RpcProtocolVersions_Version_descriptor;
-      }
-
-      protected com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
-          internalGetFieldAccessorTable() {
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-            .ensureFieldAccessorsInitialized(
-                io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.class, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.Builder.class);
-      }
-
-      public static final int MAJOR_FIELD_NUMBER = 1;
-      private int major_;
-      /**
-       * <code>uint32 major = 1;</code>
-       */
-      public int getMajor() {
-        return major_;
-      }
-
-      public static final int MINOR_FIELD_NUMBER = 2;
-      private int minor_;
-      /**
-       * <code>uint32 minor = 2;</code>
-       */
-      public int getMinor() {
-        return minor_;
-      }
-
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-                          throws java.io.IOException {
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-      public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version getDefaultInstanceForType() {
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-    }
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-    public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version getMaxRpcVersion() {
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-    public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.VersionOrBuilder getMaxRpcVersionOrBuilder() {
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-    /**
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-      // Construct using io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.newBuilder()
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-      public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions build() {
-        io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions result = buildPartial();
-        if (!result.isInitialized()) {
-          throw newUninitializedMessageException(result);
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-        return result;
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-      public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions buildPartial() {
-        io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions result = new io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions(this);
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-
-      public Builder mergeFrom(io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions other) {
-        if (other == io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.getDefaultInstance()) return this;
-        if (other.hasMaxRpcVersion()) {
-          mergeMaxRpcVersion(other.getMaxRpcVersion());
-        }
-        if (other.hasMinRpcVersion()) {
-          mergeMinRpcVersion(other.getMinRpcVersion());
-        }
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-      public final boolean isInitialized() {
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-
-      public Builder mergeFrom(
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-          com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-          throws java.io.IOException {
-        io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions parsedMessage = null;
-        try {
-          parsedMessage = PARSER.parsePartialFrom(input, extensionRegistry);
-        } catch (com.google.protobuf.InvalidProtocolBufferException e) {
-          parsedMessage = (io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions) e.getUnfinishedMessage();
-          throw e.unwrapIOException();
-        } finally {
-          if (parsedMessage != null) {
-            mergeFrom(parsedMessage);
-          }
-        }
-        return this;
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-
-      private io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version maxRpcVersion_ = null;
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.Builder, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.VersionOrBuilder> maxRpcVersionBuilder_;
-      /**
-       * <pre>
-       * Maximum supported RPC version.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
-       */
-      public boolean hasMaxRpcVersion() {
-        return maxRpcVersionBuilder_ != null || maxRpcVersion_ != null;
-      }
-      /**
-       * <pre>
-       * Maximum supported RPC version.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
-       */
-      public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version getMaxRpcVersion() {
-        if (maxRpcVersionBuilder_ == null) {
-          return maxRpcVersion_ == null ? io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.getDefaultInstance() : maxRpcVersion_;
-        } else {
-          return maxRpcVersionBuilder_.getMessage();
-        }
-      }
-      /**
-       * <pre>
-       * Maximum supported RPC version.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
-       */
-      public Builder setMaxRpcVersion(io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version value) {
-        if (maxRpcVersionBuilder_ == null) {
-          if (value == null) {
-            throw new NullPointerException();
-          }
-          maxRpcVersion_ = value;
-          onChanged();
-        } else {
-          maxRpcVersionBuilder_.setMessage(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * Maximum supported RPC version.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
-       */
-      public Builder setMaxRpcVersion(
-          io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.Builder builderForValue) {
-        if (maxRpcVersionBuilder_ == null) {
-          maxRpcVersion_ = builderForValue.build();
-          onChanged();
-        } else {
-          maxRpcVersionBuilder_.setMessage(builderForValue.build());
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * Maximum supported RPC version.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
-       */
-      public Builder mergeMaxRpcVersion(io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version value) {
-        if (maxRpcVersionBuilder_ == null) {
-          if (maxRpcVersion_ != null) {
-            maxRpcVersion_ =
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.newBuilder(maxRpcVersion_).mergeFrom(value).buildPartial();
-          } else {
-            maxRpcVersion_ = value;
-          }
-          onChanged();
-        } else {
-          maxRpcVersionBuilder_.mergeFrom(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * Maximum supported RPC version.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
-       */
-      public Builder clearMaxRpcVersion() {
-        if (maxRpcVersionBuilder_ == null) {
-          maxRpcVersion_ = null;
-          onChanged();
-        } else {
-          maxRpcVersion_ = null;
-          maxRpcVersionBuilder_ = null;
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * Maximum supported RPC version.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
-       */
-      public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.Builder getMaxRpcVersionBuilder() {
-        
-        onChanged();
-        return getMaxRpcVersionFieldBuilder().getBuilder();
-      }
-      /**
-       * <pre>
-       * Maximum supported RPC version.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
-       */
-      public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.VersionOrBuilder getMaxRpcVersionOrBuilder() {
-        if (maxRpcVersionBuilder_ != null) {
-          return maxRpcVersionBuilder_.getMessageOrBuilder();
-        } else {
-          return maxRpcVersion_ == null ?
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.getDefaultInstance() : maxRpcVersion_;
-        }
-      }
-      /**
-       * <pre>
-       * Maximum supported RPC version.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions.Version max_rpc_version = 1;</code>
-       */
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.Builder, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.VersionOrBuilder> 
-          getMaxRpcVersionFieldBuilder() {
-        if (maxRpcVersionBuilder_ == null) {
-          maxRpcVersionBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.Builder, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.VersionOrBuilder>(
-                  getMaxRpcVersion(),
-                  getParentForChildren(),
-                  isClean());
-          maxRpcVersion_ = null;
-        }
-        return maxRpcVersionBuilder_;
-      }
-
-      private io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version minRpcVersion_ = null;
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.Builder, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.VersionOrBuilder> minRpcVersionBuilder_;
-      /**
-       * <pre>
-       * Minimum supported RPC version.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
-       */
-      public boolean hasMinRpcVersion() {
-        return minRpcVersionBuilder_ != null || minRpcVersion_ != null;
-      }
-      /**
-       * <pre>
-       * Minimum supported RPC version.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
-       */
-      public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version getMinRpcVersion() {
-        if (minRpcVersionBuilder_ == null) {
-          return minRpcVersion_ == null ? io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.getDefaultInstance() : minRpcVersion_;
-        } else {
-          return minRpcVersionBuilder_.getMessage();
-        }
-      }
-      /**
-       * <pre>
-       * Minimum supported RPC version.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
-       */
-      public Builder setMinRpcVersion(io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version value) {
-        if (minRpcVersionBuilder_ == null) {
-          if (value == null) {
-            throw new NullPointerException();
-          }
-          minRpcVersion_ = value;
-          onChanged();
-        } else {
-          minRpcVersionBuilder_.setMessage(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * Minimum supported RPC version.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
-       */
-      public Builder setMinRpcVersion(
-          io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.Builder builderForValue) {
-        if (minRpcVersionBuilder_ == null) {
-          minRpcVersion_ = builderForValue.build();
-          onChanged();
-        } else {
-          minRpcVersionBuilder_.setMessage(builderForValue.build());
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * Minimum supported RPC version.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
-       */
-      public Builder mergeMinRpcVersion(io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version value) {
-        if (minRpcVersionBuilder_ == null) {
-          if (minRpcVersion_ != null) {
-            minRpcVersion_ =
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.newBuilder(minRpcVersion_).mergeFrom(value).buildPartial();
-          } else {
-            minRpcVersion_ = value;
-          }
-          onChanged();
-        } else {
-          minRpcVersionBuilder_.mergeFrom(value);
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * Minimum supported RPC version.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
-       */
-      public Builder clearMinRpcVersion() {
-        if (minRpcVersionBuilder_ == null) {
-          minRpcVersion_ = null;
-          onChanged();
-        } else {
-          minRpcVersion_ = null;
-          minRpcVersionBuilder_ = null;
-        }
-
-        return this;
-      }
-      /**
-       * <pre>
-       * Minimum supported RPC version.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
-       */
-      public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.Builder getMinRpcVersionBuilder() {
-        
-        onChanged();
-        return getMinRpcVersionFieldBuilder().getBuilder();
-      }
-      /**
-       * <pre>
-       * Minimum supported RPC version.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
-       */
-      public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.VersionOrBuilder getMinRpcVersionOrBuilder() {
-        if (minRpcVersionBuilder_ != null) {
-          return minRpcVersionBuilder_.getMessageOrBuilder();
-        } else {
-          return minRpcVersion_ == null ?
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.getDefaultInstance() : minRpcVersion_;
-        }
-      }
-      /**
-       * <pre>
-       * Minimum supported RPC version.
-       * </pre>
-       *
-       * <code>.grpc.gcp.RpcProtocolVersions.Version min_rpc_version = 2;</code>
-       */
-      private com.google.protobuf.SingleFieldBuilderV3<
-          io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.Builder, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.VersionOrBuilder> 
-          getMinRpcVersionFieldBuilder() {
-        if (minRpcVersionBuilder_ == null) {
-          minRpcVersionBuilder_ = new com.google.protobuf.SingleFieldBuilderV3<
-              io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version.Builder, io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.VersionOrBuilder>(
-                  getMinRpcVersion(),
-                  getParentForChildren(),
-                  isClean());
-          minRpcVersion_ = null;
-        }
-        return minRpcVersionBuilder_;
-      }
-      public final Builder setUnknownFields(
-          final com.google.protobuf.UnknownFieldSet unknownFields) {
-        return super.setUnknownFieldsProto3(unknownFields);
-      }
-
-      public final Builder mergeUnknownFields(
-          final com.google.protobuf.UnknownFieldSet unknownFields) {
-        return super.mergeUnknownFields(unknownFields);
-      }
-
-
-      // @@protoc_insertion_point(builder_scope:grpc.gcp.RpcProtocolVersions)
-    }
-
-    // @@protoc_insertion_point(class_scope:grpc.gcp.RpcProtocolVersions)
-    private static final io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions DEFAULT_INSTANCE;
-    static {
-      DEFAULT_INSTANCE = new io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions();
-    }
-
-    public static io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions getDefaultInstance() {
-      return DEFAULT_INSTANCE;
-    }
-
-    private static final com.google.protobuf.Parser<RpcProtocolVersions>
-        PARSER = new com.google.protobuf.AbstractParser<RpcProtocolVersions>() {
-      public RpcProtocolVersions parsePartialFrom(
-          com.google.protobuf.CodedInputStream input,
-          com.google.protobuf.ExtensionRegistryLite extensionRegistry)
-          throws com.google.protobuf.InvalidProtocolBufferException {
-        return new RpcProtocolVersions(input, extensionRegistry);
-      }
-    };
-
-    public static com.google.protobuf.Parser<RpcProtocolVersions> parser() {
-      return PARSER;
-    }
-
-    @java.lang.Override
-    public com.google.protobuf.Parser<RpcProtocolVersions> getParserForType() {
-      return PARSER;
-    }
-
-    public io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions getDefaultInstanceForType() {
-      return DEFAULT_INSTANCE;
-    }
-
-  }
-
-  private static final com.google.protobuf.Descriptors.Descriptor
-    internal_static_grpc_gcp_RpcProtocolVersions_descriptor;
-  private static final 
-    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
-      internal_static_grpc_gcp_RpcProtocolVersions_fieldAccessorTable;
-  private static final com.google.protobuf.Descriptors.Descriptor
-    internal_static_grpc_gcp_RpcProtocolVersions_Version_descriptor;
-  private static final 
-    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
-      internal_static_grpc_gcp_RpcProtocolVersions_Version_fieldAccessorTable;
-
-  public static com.google.protobuf.Descriptors.FileDescriptor
-      getDescriptor() {
-    return descriptor;
-  }
-  private static  com.google.protobuf.Descriptors.FileDescriptor
-      descriptor;
-  static {
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-      "\n(grpc/gcp/transport_security_common.pro" +
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-      "ocolVersions.Version\022>\n\017min_rpc_version\030" +
-      "\002 \001(\0132%.grpc.gcp.RpcProtocolVersions.Ver" +
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-      "\002 \001(\r*Q\n\rSecurityLevel\022\021\n\rSECURITY_NONE\020" +
-      "\000\022\022\n\016INTEGRITY_ONLY\020\001\022\031\n\025INTEGRITY_AND_P" +
-      "RIVACY\020\002B\027\n\025io.grpc.alts.internalb\006proto" +
-      "3"
-    };
-    com.google.protobuf.Descriptors.FileDescriptor.InternalDescriptorAssigner assigner =
-        new com.google.protobuf.Descriptors.FileDescriptor.    InternalDescriptorAssigner() {
-          public com.google.protobuf.ExtensionRegistry assignDescriptors(
-              com.google.protobuf.Descriptors.FileDescriptor root) {
-            descriptor = root;
-            return null;
-          }
-        };
-    com.google.protobuf.Descriptors.FileDescriptor
-      .internalBuildGeneratedFileFrom(descriptorData,
-        new com.google.protobuf.Descriptors.FileDescriptor[] {
-        }, assigner);
-    internal_static_grpc_gcp_RpcProtocolVersions_descriptor =
-      getDescriptor().getMessageTypes().get(0);
-    internal_static_grpc_gcp_RpcProtocolVersions_fieldAccessorTable = new
-      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
-        internal_static_grpc_gcp_RpcProtocolVersions_descriptor,
-        new java.lang.String[] { "MaxRpcVersion", "MinRpcVersion", });
-    internal_static_grpc_gcp_RpcProtocolVersions_Version_descriptor =
-      internal_static_grpc_gcp_RpcProtocolVersions_descriptor.getNestedTypes().get(0);
-    internal_static_grpc_gcp_RpcProtocolVersions_Version_fieldAccessorTable = new
-      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
-        internal_static_grpc_gcp_RpcProtocolVersions_Version_descriptor,
-        new java.lang.String[] { "Major", "Minor", });
-  }
-
-  // @@protoc_insertion_point(outer_class_scope)
-}
diff --git a/alts/src/generated/main/java/io/grpc/alts/internal/TransportSecurityCommonProto.java b/alts/src/generated/main/java/io/grpc/alts/internal/TransportSecurityCommonProto.java
new file mode 100644
index 0000000000..878b805296
--- /dev/null
+++ b/alts/src/generated/main/java/io/grpc/alts/internal/TransportSecurityCommonProto.java
@@ -0,0 +1,76 @@
+// Generated by the protocol buffer compiler.  DO NOT EDIT!
+// source: grpc/gcp/transport_security_common.proto
+
+package io.grpc.alts.internal;
+
+public final class TransportSecurityCommonProto {
+  private TransportSecurityCommonProto() {}
+  public static void registerAllExtensions(
+      com.google.protobuf.ExtensionRegistryLite registry) {
+  }
+
+  public static void registerAllExtensions(
+      com.google.protobuf.ExtensionRegistry registry) {
+    registerAllExtensions(
+        (com.google.protobuf.ExtensionRegistryLite) registry);
+  }
+  static final com.google.protobuf.Descriptors.Descriptor
+    internal_static_grpc_gcp_RpcProtocolVersions_descriptor;
+  static final 
+    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internal_static_grpc_gcp_RpcProtocolVersions_fieldAccessorTable;
+  static final com.google.protobuf.Descriptors.Descriptor
+    internal_static_grpc_gcp_RpcProtocolVersions_Version_descriptor;
+  static final 
+    com.google.protobuf.GeneratedMessageV3.FieldAccessorTable
+      internal_static_grpc_gcp_RpcProtocolVersions_Version_fieldAccessorTable;
+
+  public static com.google.protobuf.Descriptors.FileDescriptor
+      getDescriptor() {
+    return descriptor;
+  }
+  private static  com.google.protobuf.Descriptors.FileDescriptor
+      descriptor;
+  static {
+    java.lang.String[] descriptorData = {
+      "\n(grpc/gcp/transport_security_common.pro" +
+      "to\022\010grpc.gcp\"\276\001\n\023RpcProtocolVersions\022>\n\017" +
+      "max_rpc_version\030\001 \001(\0132%.grpc.gcp.RpcProt" +
+      "ocolVersions.Version\022>\n\017min_rpc_version\030" +
+      "\002 \001(\0132%.grpc.gcp.RpcProtocolVersions.Ver" +
+      "sion\032\'\n\007Version\022\r\n\005major\030\001 \001(\r\022\r\n\005minor\030" +
+      "\002 \001(\r*Q\n\rSecurityLevel\022\021\n\rSECURITY_NONE\020" +
+      "\000\022\022\n\016INTEGRITY_ONLY\020\001\022\031\n\025INTEGRITY_AND_P" +
+      "RIVACY\020\002Bx\n\025io.grpc.alts.internalB\034Trans" +
+      "portSecurityCommonProtoP\001Z?google.golang" +
+      ".org/grpc/credentials/alts/internal/prot" +
+      "o/grpc_gcpb\006proto3"
+    };
+    com.google.protobuf.Descriptors.FileDescriptor.InternalDescriptorAssigner assigner =
+        new com.google.protobuf.Descriptors.FileDescriptor.    InternalDescriptorAssigner() {
+          public com.google.protobuf.ExtensionRegistry assignDescriptors(
+              com.google.protobuf.Descriptors.FileDescriptor root) {
+            descriptor = root;
+            return null;
+          }
+        };
+    com.google.protobuf.Descriptors.FileDescriptor
+      .internalBuildGeneratedFileFrom(descriptorData,
+        new com.google.protobuf.Descriptors.FileDescriptor[] {
+        }, assigner);
+    internal_static_grpc_gcp_RpcProtocolVersions_descriptor =
+      getDescriptor().getMessageTypes().get(0);
+    internal_static_grpc_gcp_RpcProtocolVersions_fieldAccessorTable = new
+      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
+        internal_static_grpc_gcp_RpcProtocolVersions_descriptor,
+        new java.lang.String[] { "MaxRpcVersion", "MinRpcVersion", });
+    internal_static_grpc_gcp_RpcProtocolVersions_Version_descriptor =
+      internal_static_grpc_gcp_RpcProtocolVersions_descriptor.getNestedTypes().get(0);
+    internal_static_grpc_gcp_RpcProtocolVersions_Version_fieldAccessorTable = new
+      com.google.protobuf.GeneratedMessageV3.FieldAccessorTable(
+        internal_static_grpc_gcp_RpcProtocolVersions_Version_descriptor,
+        new java.lang.String[] { "Major", "Minor", });
+  }
+
+  // @@protoc_insertion_point(outer_class_scope)
+}
diff --git a/alts/src/main/java/io/grpc/alts/internal/AltsAuthContext.java b/alts/src/main/java/io/grpc/alts/internal/AltsAuthContext.java
index cc335fe96d..4cd06c4b4e 100644
--- a/alts/src/main/java/io/grpc/alts/internal/AltsAuthContext.java
+++ b/alts/src/main/java/io/grpc/alts/internal/AltsAuthContext.java
@@ -17,10 +17,10 @@
 package io.grpc.alts.internal;
 
 import com.google.common.annotations.VisibleForTesting;
-import io.grpc.alts.internal.Altscontext.AltsContext;
-import io.grpc.alts.internal.Handshaker.HandshakerResult;
-import io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions;
-import io.grpc.alts.internal.TransportSecurityCommon.SecurityLevel;
+import io.grpc.alts.internal.AltsContext;
+import io.grpc.alts.internal.HandshakerResult;
+import io.grpc.alts.internal.RpcProtocolVersions;
+import io.grpc.alts.internal.SecurityLevel;
 
 /** AltsAuthContext contains security-related context information about an ALTs connection. */
 public final class AltsAuthContext {
diff --git a/alts/src/main/java/io/grpc/alts/internal/AltsClientOptions.java b/alts/src/main/java/io/grpc/alts/internal/AltsClientOptions.java
index e70e7d9ddb..9ad614c962 100644
--- a/alts/src/main/java/io/grpc/alts/internal/AltsClientOptions.java
+++ b/alts/src/main/java/io/grpc/alts/internal/AltsClientOptions.java
@@ -17,7 +17,6 @@
 package io.grpc.alts.internal;
 
 import com.google.common.collect.ImmutableList;
-import io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions;
 import javax.annotation.Nullable;
 
 /** Handshaker options for creating ALTS client channel. */
diff --git a/alts/src/main/java/io/grpc/alts/internal/AltsHandshakerClient.java b/alts/src/main/java/io/grpc/alts/internal/AltsHandshakerClient.java
index 8f1d79bf0a..26dcde3873 100644
--- a/alts/src/main/java/io/grpc/alts/internal/AltsHandshakerClient.java
+++ b/alts/src/main/java/io/grpc/alts/internal/AltsHandshakerClient.java
@@ -21,15 +21,6 @@ import com.google.common.base.Preconditions;
 import com.google.common.base.Strings;
 import com.google.protobuf.ByteString;
 import io.grpc.Status;
-import io.grpc.alts.internal.Handshaker.HandshakeProtocol;
-import io.grpc.alts.internal.Handshaker.HandshakerReq;
-import io.grpc.alts.internal.Handshaker.HandshakerResp;
-import io.grpc.alts.internal.Handshaker.HandshakerResult;
-import io.grpc.alts.internal.Handshaker.HandshakerStatus;
-import io.grpc.alts.internal.Handshaker.NextHandshakeMessageReq;
-import io.grpc.alts.internal.Handshaker.ServerHandshakeParameters;
-import io.grpc.alts.internal.Handshaker.StartClientHandshakeReq;
-import io.grpc.alts.internal.Handshaker.StartServerHandshakeReq;
 import io.grpc.alts.internal.HandshakerServiceGrpc.HandshakerServiceStub;
 import java.io.IOException;
 import java.nio.ByteBuffer;
diff --git a/alts/src/main/java/io/grpc/alts/internal/AltsHandshakerOptions.java b/alts/src/main/java/io/grpc/alts/internal/AltsHandshakerOptions.java
index 5e0dbdbe29..d50f92f185 100644
--- a/alts/src/main/java/io/grpc/alts/internal/AltsHandshakerOptions.java
+++ b/alts/src/main/java/io/grpc/alts/internal/AltsHandshakerOptions.java
@@ -16,7 +16,6 @@
 
 package io.grpc.alts.internal;
 
-import io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions;
 import javax.annotation.Nullable;
 
 /** Handshaker options for creating ALTS channel. */
diff --git a/alts/src/main/java/io/grpc/alts/internal/AltsHandshakerStub.java b/alts/src/main/java/io/grpc/alts/internal/AltsHandshakerStub.java
index ee979aa433..5dc31919fe 100644
--- a/alts/src/main/java/io/grpc/alts/internal/AltsHandshakerStub.java
+++ b/alts/src/main/java/io/grpc/alts/internal/AltsHandshakerStub.java
@@ -18,8 +18,6 @@ package io.grpc.alts.internal;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Optional;
-import io.grpc.alts.internal.Handshaker.HandshakerReq;
-import io.grpc.alts.internal.Handshaker.HandshakerResp;
 import io.grpc.alts.internal.HandshakerServiceGrpc.HandshakerServiceStub;
 import io.grpc.stub.StreamObserver;
 import java.io.IOException;
diff --git a/alts/src/main/java/io/grpc/alts/internal/RpcProtocolVersionsUtil.java b/alts/src/main/java/io/grpc/alts/internal/RpcProtocolVersionsUtil.java
index b685b6b2d3..005065b4e2 100644
--- a/alts/src/main/java/io/grpc/alts/internal/RpcProtocolVersionsUtil.java
+++ b/alts/src/main/java/io/grpc/alts/internal/RpcProtocolVersionsUtil.java
@@ -17,8 +17,7 @@
 package io.grpc.alts.internal;
 
 import com.google.common.annotations.VisibleForTesting;
-import io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions;
-import io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version;
+import io.grpc.alts.internal.RpcProtocolVersions.Version;
 import javax.annotation.Nullable;
 
 /** Utility class for Rpc Protocol Versions. */
diff --git a/alts/src/main/proto/grpc/gcp/altscontext.proto b/alts/src/main/proto/grpc/gcp/altscontext.proto
index ab22a03968..98ef21cacd 100644
--- a/alts/src/main/proto/grpc/gcp/altscontext.proto
+++ b/alts/src/main/proto/grpc/gcp/altscontext.proto
@@ -12,12 +12,18 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// The canonical version of this proto can be found at
+// https://github.com/grpc/grpc-proto/blob/master/grpc/gcp/altscontext.proto
+
 syntax = "proto3";
 
 package grpc.gcp;
 
 import "grpc/gcp/transport_security_common.proto";
 
+option go_package = "google.golang.org/grpc/credentials/alts/internal/proto/grpc_gcp";
+option java_multiple_files = true;
+option java_outer_classname = "AltsContextProto";
 option java_package = "io.grpc.alts.internal";
 
 message AltsContext {
@@ -42,3 +48,4 @@ message AltsContext {
   // Additional attributes of the peer.
   map<string, string> peer_attributes = 7;
 }
+
diff --git a/alts/src/main/proto/grpc/gcp/handshaker.proto b/alts/src/main/proto/grpc/gcp/handshaker.proto
index bb057c6cb2..a29024ffce 100644
--- a/alts/src/main/proto/grpc/gcp/handshaker.proto
+++ b/alts/src/main/proto/grpc/gcp/handshaker.proto
@@ -12,14 +12,21 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// The canonical version of this proto can be found at
+// https://github.com/grpc/grpc-proto/blob/master/grpc/gcp/handshaker.proto
+
 syntax = "proto3";
 
 package grpc.gcp;
 
 import "grpc/gcp/transport_security_common.proto";
 
+option go_package = "google.golang.org/grpc/credentials/alts/internal/proto/grpc_gcp";
+option java_multiple_files = true;
+option java_outer_classname = "HandshakerProto";
 option java_package = "io.grpc.alts.internal";
 
+
 enum HandshakeProtocol {
   // Default value.
   HANDSHAKE_PROTOCOL_UNSPECIFIED = 0;
@@ -222,6 +229,7 @@ service HandshakerService {
   // service expects to respond. Client does not have to wait for service's
   // response before sending next request.
   rpc DoHandshake(stream HandshakerReq)
-      returns (stream HandshakerResp) {
+    returns (stream HandshakerResp) {
   }
 }
+
diff --git a/alts/src/main/proto/grpc/gcp/transport_security_common.proto b/alts/src/main/proto/grpc/gcp/transport_security_common.proto
index e10197159e..f328a51c54 100644
--- a/alts/src/main/proto/grpc/gcp/transport_security_common.proto
+++ b/alts/src/main/proto/grpc/gcp/transport_security_common.proto
@@ -12,10 +12,16 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// The canonical version of this proto can be found at
+// https://github.com/grpc/grpc-proto/blob/master/grpc/gcp/transport_security_common.proto
+
 syntax = "proto3";
 
 package grpc.gcp;
 
+option go_package = "google.golang.org/grpc/credentials/alts/internal/proto/grpc_gcp";
+option java_multiple_files = true;
+option java_outer_classname = "TransportSecurityCommonProto";
 option java_package = "io.grpc.alts.internal";
 
 // The security level of the created channel. The list is sorted in increasing
@@ -38,3 +44,4 @@ message RpcProtocolVersions {
   // Minimum supported RPC version.
   Version min_rpc_version = 2;
 }
+
diff --git a/alts/src/test/java/io/grpc/alts/internal/AltsAuthContextTest.java b/alts/src/test/java/io/grpc/alts/internal/AltsAuthContextTest.java
index eb1fbf9cac..2fc2c43464 100644
--- a/alts/src/test/java/io/grpc/alts/internal/AltsAuthContextTest.java
+++ b/alts/src/test/java/io/grpc/alts/internal/AltsAuthContextTest.java
@@ -18,10 +18,6 @@ package io.grpc.alts.internal;
 
 import static org.junit.Assert.assertEquals;
 
-import io.grpc.alts.internal.Handshaker.HandshakerResult;
-import io.grpc.alts.internal.Handshaker.Identity;
-import io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions;
-import io.grpc.alts.internal.TransportSecurityCommon.SecurityLevel;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
diff --git a/alts/src/test/java/io/grpc/alts/internal/AltsClientOptionsTest.java b/alts/src/test/java/io/grpc/alts/internal/AltsClientOptionsTest.java
index 5a7cf84913..47d7fc79ea 100644
--- a/alts/src/test/java/io/grpc/alts/internal/AltsClientOptionsTest.java
+++ b/alts/src/test/java/io/grpc/alts/internal/AltsClientOptionsTest.java
@@ -19,7 +19,6 @@ package io.grpc.alts.internal;
 import static com.google.common.truth.Truth.assertThat;
 
 import com.google.common.collect.ImmutableList;
-import io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
diff --git a/alts/src/test/java/io/grpc/alts/internal/AltsHandshakerClientTest.java b/alts/src/test/java/io/grpc/alts/internal/AltsHandshakerClientTest.java
index 41923b5467..a8eb48ad26 100644
--- a/alts/src/test/java/io/grpc/alts/internal/AltsHandshakerClientTest.java
+++ b/alts/src/test/java/io/grpc/alts/internal/AltsHandshakerClientTest.java
@@ -29,11 +29,6 @@ import static org.mockito.Mockito.when;
 
 import com.google.common.collect.ImmutableList;
 import com.google.protobuf.ByteString;
-import io.grpc.alts.internal.Handshaker.HandshakeProtocol;
-import io.grpc.alts.internal.Handshaker.HandshakerReq;
-import io.grpc.alts.internal.Handshaker.Identity;
-import io.grpc.alts.internal.Handshaker.StartClientHandshakeReq;
-import io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions;
 import java.nio.ByteBuffer;
 import java.security.GeneralSecurityException;
 import org.junit.Before;
diff --git a/alts/src/test/java/io/grpc/alts/internal/AltsHandshakerOptionsTest.java b/alts/src/test/java/io/grpc/alts/internal/AltsHandshakerOptionsTest.java
index 6a7814b300..ab065f2f2e 100644
--- a/alts/src/test/java/io/grpc/alts/internal/AltsHandshakerOptionsTest.java
+++ b/alts/src/test/java/io/grpc/alts/internal/AltsHandshakerOptionsTest.java
@@ -18,7 +18,6 @@ package io.grpc.alts.internal;
 
 import static com.google.common.truth.Truth.assertThat;
 
-import io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
diff --git a/alts/src/test/java/io/grpc/alts/internal/AltsHandshakerStubTest.java b/alts/src/test/java/io/grpc/alts/internal/AltsHandshakerStubTest.java
index b896b5bf77..2267a765a9 100644
--- a/alts/src/test/java/io/grpc/alts/internal/AltsHandshakerStubTest.java
+++ b/alts/src/test/java/io/grpc/alts/internal/AltsHandshakerStubTest.java
@@ -21,9 +21,6 @@ import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.fail;
 
 import com.google.protobuf.ByteString;
-import io.grpc.alts.internal.Handshaker.HandshakerReq;
-import io.grpc.alts.internal.Handshaker.HandshakerResp;
-import io.grpc.alts.internal.Handshaker.NextHandshakeMessageReq;
 import io.grpc.stub.StreamObserver;
 import java.io.IOException;
 import org.junit.Before;
diff --git a/alts/src/test/java/io/grpc/alts/internal/AltsProtocolNegotiatorTest.java b/alts/src/test/java/io/grpc/alts/internal/AltsProtocolNegotiatorTest.java
index 88f64784be..e92a2f9412 100644
--- a/alts/src/test/java/io/grpc/alts/internal/AltsProtocolNegotiatorTest.java
+++ b/alts/src/test/java/io/grpc/alts/internal/AltsProtocolNegotiatorTest.java
@@ -27,7 +27,6 @@ import io.grpc.Attributes;
 import io.grpc.Grpc;
 import io.grpc.InternalChannelz;
 import io.grpc.SecurityLevel;
-import io.grpc.alts.internal.Handshaker.HandshakerResult;
 import io.grpc.alts.internal.TsiFrameProtector.Consumer;
 import io.grpc.alts.internal.TsiPeer.Property;
 import io.grpc.internal.GrpcAttributes;
diff --git a/alts/src/test/java/io/grpc/alts/internal/AltsTsiHandshakerTest.java b/alts/src/test/java/io/grpc/alts/internal/AltsTsiHandshakerTest.java
index ac3dfb8f2d..627e52a6db 100644
--- a/alts/src/test/java/io/grpc/alts/internal/AltsTsiHandshakerTest.java
+++ b/alts/src/test/java/io/grpc/alts/internal/AltsTsiHandshakerTest.java
@@ -26,9 +26,6 @@ import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
 import com.google.protobuf.ByteString;
-import io.grpc.alts.internal.Handshaker.HandshakerResult;
-import io.grpc.alts.internal.Handshaker.Identity;
-import io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions;
 import java.nio.ByteBuffer;
 import org.junit.Before;
 import org.junit.Test;
diff --git a/alts/src/test/java/io/grpc/alts/internal/AltsTsiTest.java b/alts/src/test/java/io/grpc/alts/internal/AltsTsiTest.java
index 8d990bda88..a6832ad8de 100644
--- a/alts/src/test/java/io/grpc/alts/internal/AltsTsiTest.java
+++ b/alts/src/test/java/io/grpc/alts/internal/AltsTsiTest.java
@@ -20,9 +20,6 @@ import static org.junit.Assert.assertEquals;
 
 import com.google.common.testing.GcFinalization;
 import io.grpc.alts.internal.ByteBufTestUtils.RegisterRef;
-import io.grpc.alts.internal.Handshaker.HandshakeProtocol;
-import io.grpc.alts.internal.Handshaker.HandshakerReq;
-import io.grpc.alts.internal.Handshaker.HandshakerResp;
 import io.grpc.alts.internal.TsiTest.Handshakers;
 import io.netty.buffer.ByteBuf;
 import io.netty.util.ReferenceCounted;
diff --git a/alts/src/test/java/io/grpc/alts/internal/MockAltsHandshakerResp.java b/alts/src/test/java/io/grpc/alts/internal/MockAltsHandshakerResp.java
index 205746690d..7843d68120 100644
--- a/alts/src/test/java/io/grpc/alts/internal/MockAltsHandshakerResp.java
+++ b/alts/src/test/java/io/grpc/alts/internal/MockAltsHandshakerResp.java
@@ -20,10 +20,6 @@ import static java.nio.charset.StandardCharsets.UTF_8;
 
 import com.google.protobuf.ByteString;
 import io.grpc.Status;
-import io.grpc.alts.internal.Handshaker.HandshakerResp;
-import io.grpc.alts.internal.Handshaker.HandshakerResult;
-import io.grpc.alts.internal.Handshaker.HandshakerStatus;
-import io.grpc.alts.internal.Handshaker.Identity;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.security.SecureRandom;
diff --git a/alts/src/test/java/io/grpc/alts/internal/RpcProtocolVersionsUtilTest.java b/alts/src/test/java/io/grpc/alts/internal/RpcProtocolVersionsUtilTest.java
index dc3c7eb5d8..07e0358e70 100644
--- a/alts/src/test/java/io/grpc/alts/internal/RpcProtocolVersionsUtilTest.java
+++ b/alts/src/test/java/io/grpc/alts/internal/RpcProtocolVersionsUtilTest.java
@@ -20,9 +20,8 @@ import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
+import io.grpc.alts.internal.RpcProtocolVersions.Version;
 import io.grpc.alts.internal.RpcProtocolVersionsUtil.RpcVersionsCheckResult;
-import io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions;
-import io.grpc.alts.internal.TransportSecurityCommon.RpcProtocolVersions.Version;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;