syntax = "proto3";

package chat;

message SignedPreKey {
  bytes signed_pre_key = 1;
  uint32 version = 2;
}

// X3DH prekey bundle
message Bundle {
  // Identity key
  bytes identity = 1;
  // Installation id
  map<string,SignedPreKey> signed_pre_keys = 2;
  // Prekey signature
  bytes signature = 4;
}

message BundleContainer {
  // X3DH prekey bundle
  Bundle bundle = 1;
  // Private signed prekey
  bytes private_signed_pre_key = 2;

  // Local time creation
  int64 timestamp = 3;
}

message DRHeader {
  // Current ratchet public key
  bytes key = 1;
  // Number of the message in the sending chain
  uint32 n = 2;
  // Length of the previous sending chain
  uint32 pn = 3;
  // Bundle ID
  bytes id = 4;
}

message DHHeader {
  // Compressed ephemeral public key
  bytes key = 1;
}

message X3DHHeader {
  // Ephemeral key used
  bytes key = 1;
  // Used bundle's signed prekey
  bytes id = 4;
  // The device id
  string installation_id = 3;
}

// Direct message value
message DirectMessageProtocol {
  X3DHHeader X3DH_header = 1;
  DRHeader DR_header = 2;
  DHHeader DH_header = 101;
  // Encrypted payload
  bytes payload = 3;
}

// Top-level protocol message
message ProtocolMessage {
  // An optional bundle is exchanged with each message
  Bundle bundle = 1;

  // One to one message, encrypted, indexed by installation_id
  map<string,DirectMessageProtocol> direct_message = 101;

  // Public chats, not encrypted
  bytes public_message = 102;
}