“Apple says it will work with the GSMA members on ways to further improve the RCS protocol. This particularly includes improving the security and encryption of RCS messages. Apple also told 9to5Mac that it will not use any sort of proprietary end-to-end encryption on top of RCS. Its focus is on improving the RCS standard itself. For comparison’s sake, Google’s implementation of end-to-end encryption is part of the Messages app on Android rather than the RCS spec itself. ”
Source : Apple announces that RCS support is coming to iPhone next year – 9to5Mac