go-zeolite

Zeolite: simple & secure communications based on libsodium with perfect forward secrecy, XChaCha20-Poly1305 and a mirrored protocol (no distinction between client & server).

Protocol design

The protocol is completely identical for server & client.

Handshake (performed in lockstep by both participants)

1. Protocol version (currently zeolite1, so 8 bytes)
2. Public key (32 bytes)
3. Ephemeral key (for PFS) signed with public key (96 bytes)
4. Symmetric key (for communication) encrypted with ephemeral key (72 bytes)
5. Stream header (24 bytes)

Total: 232 bytes

Data Transmission

1. Message size (4 bytes)
2. Encrypted message (17 bytes + message size)

Total: 21 bytes + message size