SEAM - Simple Encrypted Authenticated Messaging

⚠️ WARNING: THIS IS ALPHA SOFTWARE AND HAS NOT BEEN AUDITED. USE AT YOUR OWN RISK. ⚠️

The SEAM library implements a small encoding standard for exchanging messages signed and encrypted with TweetNaCl (and compatible) constructions: sign, box, and secretbox.

SEAM is designed to enable two messaging modes.

1. In direct message (or "DM") mode, messages are encrypted with the box construction (x25519-xsalsa20-poly1305) using the recipient's public key and an ephemeral private key (the "transit" key).

{
  "mode": "direct",
  "body": "(base64-encoded encrypted bytes)",
  "destination": "(opaque string)",
  "nonce": "(base64-encoded nonce bytes)",
  "timestamp": 2234567890,
  "transitIdentity": "(base64-encoded X25519 public key)"
}

2. In shared message (or "thread") mode, messages are encrypted with the secretbox construction (xsalsa20-poly1305) using a shared key.

{
  "mode": "shared",
  "body": "(base64-encoded encrypted bytes)",
  "destination": "(opaque string)",
  "nonce": "(base64-encoded nonce bytes)",
  "timestamp": 2234567890
}

All messages are encoded as JSON, digested with SHA512, signed with the sign construction (ed25519), and wrapped in an envelope with the signing user's public key.

{
  "author": "(base64-encoded ed25519 public key)",
  "message": "(message JSON)",
  "signature": "(base64-encoded ed25519 signature of SHA-512 hash of message JSON)"
}

See GoDoc for full usage.

License

Released under The MIT License (see LICENSE.txt).

Copyright 2020 Duncan Smith