WhisperPush: Secure Messaging Integration

Very neat indeed. Integrating at a low level like that is an excellent plan for a good user experience.

Without diving into the code they link to, I wonder how it falls back to normal SMS for clients which are not using CM/TextSecure. They couldn't just send it encrypted in case the receiving client doesn't support that. So, they must negotiate which version to send (encrypted vs unencrypted). Apparently, this handshake/negotiation works with regular SMS. Anyone have any insight?

Also, I think it is important to note that the SMS messages are only encrypted in transit and not at rest. I believe this to be the case because the article says that I can use any SMS client I want. Also, encryption at rest would kill searchability, back-up/transfer to new device, etc.

Edit: I didn't mean to imply that encryption during transit is anything to scoff at. It is quite excellent compared to what people have now, which is no protection at all!