New Version of RCS Specification Includes End-to-End Encryption ⇥ gsma.com

Tom Van Pelt, technical director at GSMA:

In my last post, ‘RCS Now in iOS: a New Chapter for Mobile Messaging‘, I celebrated the integration of Rich Communication Services (RCS) with Apple’s iOS 18, a culmination of years of collaboration across mobile operators, device manufacturers, and technology providers. Today, I am pleased to announce the next milestone: the availability of new GSMA specifications for RCS that include end-to-end encryption (E2EE) based on the Messaging Layer Security (MLS) protocol.

The GSMA has published a separate specification (PDF) for end-to-end encryption, distinct from that of RCS itself.

Google announced its support for MLS in 2023, though it is still building integration with Google Messages. Apple has also committed to the updated spec. This is great news. It made sense to wait until encryption was part of the official spec.

Speaking of which, the spec says (PDF) that if both parties have enabled end-to-end encryption and a message cannot be delivered over RCS, carriers will not fall back to SMS. This helps answer one part of the main question I have, which is how all of this will be differentiated to users now that there will be three standards: SMS, RCS, and end-to-end encrypted RCS. Also, because this is carrier dependent, I suspect the rollout of end-to-end encryption will be a little rocky for a beat and, in some countries, never made available.