iMessage does store a secure key locally on your device which never leaves. The main difference with iMessage is Apple is able to add more signing keys to decry

iMessage does store a secure key locally on your device which never leaves. The main difference with iMessage is Apple is able to add more signing keys to decrypt the data if they wanted. This is what happens when you add a new device. In a no-trust model once you sign in on a new device you wouldn't see all of your old messages. Because all of your old messages are decrypted and sent to the new device this is evidence that a new signing key was added to the communication chain. Apple could also do this to decrypt your messages to give to a government agency or for whatever purposes they want without notifying you. https://techcrunch.com/2014/02/27/apple-explains-exactly-how-secure-imessage-really-is/ https://techcrunch.com/2014/02/27/apple-explains-exactly-how...