Any reason why you're still only using AES-128? Is that secure enough for the time being?
https://github.com/WhisperSystems/TextSecure/wiki/Protocol
https://github.com/WhisperSystems/RedPhone/wiki/Encryption-P...
https://github.com/WhisperSystems/TextSecure/wiki/Protocol
https://github.com/WhisperSystems/RedPhone/wiki/Encryption-P...
What else would you suggest?