I hope to god that amongst the overhaul they have stuck to the remit and not added any bonus features to iMessage cryptography

Today, we’d like to share an overview of our next significant advance in iMessage security: Contact Key Verification, a new feature that’s designed to detect sophisticated attacks against iMessage servers and allow users to verify that they’re messaging only with whom they intend.

https://security.apple.com/blog/imessage-contact-key-verification/