There is no interoperability between systems that use ideas from Signal Protocol and it is unlikely that there will ever be. There is no published standard. The

There is no interoperability between systems that use ideas from Signal Protocol and it is unlikely that there will ever be. There is no published standard. The best you can do is transiterate existing source code. It is a very complicated protocol with lots of state. It requires a server infrastructure to work. To be interoperable clients need access to information on the same server. The protocol is simply not designed for interoperability...