syntax = "proto3";
package header;

enum CipherMode {
  ChaChaPoly = 0;
  AESGCM = 1;
}

enum HashMode {
  BLAKE2b = 0;
  BLAKE2s = 1;
  SHA512 = 2;
  SHA256 = 3;
}

// this is the file header for encrypted files. Note that we deliberately fixed
// the DH function to ed25519 since it provides same level of security as ed448,
// but performance is better. The default choise of if all the parameters are
// default value: Noise_X_25519_ChaChaPoly_BLAKE2b. This fits the most of the
// security standards. However, initiator and responder can use a pre shared key
// for extra level of security.
message Header {
  // cipher function used by noise protocol
  CipherMode cipher = 1;
  // hash function used by noise protocol
  HashMode hash = 2;
  // if true, we will do a Xpsk1. Note user shall provide the psk upon Session::new.
  // <- s
  // ...
  // -> e, es, s, ss, psk
  bool use_psk = 3;
  // handshake message from the initiator
  bytes handshake_message = 4;
}