// Copyright 2023 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

syntax = "proto2";

package securegcm;

option optimize_for = LITE_RUNTIME;
option java_package = "com.google.security.cryptauth.lib.securegcm";
option java_outer_classname = "SecureGcmProto";
option objc_class_prefix = "SGCM";

enum Type {
  ENROLLMENT = 0;
  TICKLE = 1;
  TX_REQUEST = 2;
  TX_REPLY = 3;
  TX_SYNC_REQUEST = 4;
  TX_SYNC_RESPONSE = 5;
  TX_PING = 6;
  DEVICE_INFO_UPDATE = 7;
  TX_CANCEL_REQUEST = 8;

  // DEPRECATED (can be re-used after Aug 2015)
  PROXIMITYAUTH_PAIRING = 10;

  // The kind of identity assertion generated by a "GCM V1" device (i.e.,
  // an Android phone that has registered with us a public and a symmetric
  // key)
  GCMV1_IDENTITY_ASSERTION = 11;

  // Device-to-device communications are protected by an unauthenticated
  // Diffie-Hellman exchange. The InitiatorHello message is simply the
  // initiator's public DH key, and is not encoded as a SecureMessage, so
  // it doesn't have a tag.
  // The ResponderHello message (which is sent by the responder
  // to the initiator), on the other hand, carries a payload that is protected
  // by the derived shared key. It also contains the responder's
  // public DH key. ResponderHelloAndPayload messages have the
  // DEVICE_TO_DEVICE_RESPONDER_HELLO tag.
  DEVICE_TO_DEVICE_RESPONDER_HELLO_PAYLOAD = 12;

  // Device-to-device communications are protected by an unauthenticated
  // Diffie-Hellman exchange. Once the initiator and responder
  // agree on a shared key (through Diffie-Hellman), they will use messages
  // tagged with DEVICE_TO_DEVICE_MESSAGE to exchange data.
  DEVICE_TO_DEVICE_MESSAGE = 13;

  // Notification to let a device know it should contact a nearby device.
  DEVICE_PROXIMITY_CALLBACK = 14;

  // Device-to-device communications are protected by an unauthenticated
  // Diffie-Hellman exchange. During device-to-device authentication, the first
  // message from initiator (the challenge) is signed and put into the payload
  // of the message sent back to the initiator.
  UNLOCK_KEY_SIGNED_CHALLENGE = 15;

  // Specialty (corp only) features
  LOGIN_NOTIFICATION = 101;
}

message GcmMetadata {
  required Type type = 1;
  optional int32 version = 2 [default = 0];
}