// Taken from https://xmpp.org/extensions/xep-0384.html#protobuf-schema
message OMEMOMessage {
    required uint32 n          = 1;
    required uint32 pn         = 2;
    required bytes  dh_pub     = 3;
    optional bytes  ciphertext = 4;
}

message OMEMOAuthenticatedMessage {
    required bytes mac     = 1;
    required bytes message = 2; // Byte-encoding of an OMEMOMessage
}

message OMEMOKeyExchange {
    required uint32 pk_id  = 1;
    required uint32 spk_id = 2;
    required bytes  ik     = 3;
    required bytes  ek     = 4;
    required OMEMOAuthenticatedMessage message = 5;
}