At Open Whisper Systems, we’ve been working on improving our encrypted asynchronous chat protocol for TextSecure.
The TextSecure protocol was originally a derivative of OTR,
with minor changes to accommodate it for transports with constraints like SMS or Push. Some of the recent
changes we’ve made include
simplifying and improving OTR’s deniability, as well as
creating a key exchange mechanism for asynchronous transports.
Our most recent change incorporates what we believe to be substantial improvements to OTR’s forward secrecy “ratchet.”