Signal/TextSecure (/DRA/Axolotl) has a pretty strong throughline from the "off-the-record" protocol (OTR) from 2004/2005. Signal themselves describes TextSecure

Signal/TextSecure (/DRA/Axolotl) has a pretty strong throughline from the "off-the-record" protocol (OTR) from 2004/2005. Signal themselves describes TextSecure as a derivative of OTR (https://signal.org/blog/simplifying-otr-deniability/ https://signal.org/blog/simplifying-otr-deniability/). It's close enough that if, say, a novel attack against OTR were discovered today, the first thing I'd want to know is if there are any implications against Signal.