Comment Re:Key exchange (Score 2) 196
Apple retains the keys for all of your devices, which is how one iMessage can be sent to multiple devices.
Do you actually know this, or is this your guess? Because my understanding is that iMessage encryption was designed explicitly to avoid having Apple hold the kind of private keys that can decrypt the message. I thought there was some scheme where each device got its own decryption key, and that those keys never left the device.
Add to that that iMessage silently falls back to SMS,
Well, not entirely "silently". Messages sent via SMS turn green, so you know whether they were sent via iMessage. You don't necessarily know ahead of time whether, when you hit "Send", your message will be sent via SMS or iMessage, but I believe that can also be turned off on the device itself, so that it won't fall back to SMS.