These days, probably read this instead:<p><a href="https://signal.org/docs/specifications/doubleratchet/" rel="nofollow">https://signal.org/docs/specifications/doubleratchet/</a><p>Also the IETF drafts for MLS might be interesting:<p><a href="https://datatracker.ietf.org/doc/draft-ietf-mls-protocol/" rel="nofollow">https://datatracker.ietf.org/doc/draft-ietf-mls-protocol/</a>