- OMEMO version 0.3.0 uses the original libsignal-protocol-c implementation with its protocol versions 2 and 3.
- OMEMO version 0.4.0+ is implemented using a new protocol version 4 internally. In comparison with protocol version 3, it changes:
- HKDF info strings
- Protocol buffer encoding
- Signature scheme (uses XEd25519 instead of custom "Curve25519 signatures")
- Specification-compliant double ratchet
- Support for Ed25519 public keys
- Various serializations
- Removes unused functionality