ActivityPub is extensible, though. As part of our E2EE program, Mallory, Tom and I adapted the Messaging Layer Security (MLS) standard as an extension of ActivityPub to make the MLS over ActivityPub specification. The protocol fits the great MLS E2EE system onto the ActivityPub API and federation protocol.

But a protocol specification is not enough; it must be implemented. That’s why we’re so happy to announce that the Sovereign Tech Fund has commissioned work with the Social Web Foundation to coordinate two new interoperable implementations of MLS over ActivityPub. This investment by the Sovereign Tech Fund will help move the Fediverse towards more privacy for social web users, no matter what server they use.