Yes. As does iMessage. To my knowledge neither proprietary backend is open, but I would love to be proven wrong :) From a cursory search the best reference I c

Yes. As does iMessage. To my knowledge neither proprietary backend is open, but I would love to be proven wrong :) From a cursory search the best reference I could find was google’s whitepaper[1]: > In order to store and exchange user public keys like identity keys and prekeys, we need to have a central key server. Unlike the RCS messaging servers, the key server is currently only hosted by Google [1]: https://www.gstatic.com/messages/papers/messages_e2ee.pdf https://www.gstatic.com/messages/papers/messages_e2ee.pdf [2]: https://www.xda-developers.com/google-messages-rcs-api-third-party-apps/amp/ https://www.xda-developers.com/google-messages-rcs-api-third...