It seems that it is that time of year again, when Juliano and Thai present their most recent attack against crypto system. Last year, it was BEAST. This year, it’s CRIME, a practical attack against how TLS is used in browsers. In a wider sense, the same attack conceptually applies to any encrypted protocol where the attacker controls what is being communicated.
Initially, it was only known that the attack builds on top of an information leakage weakness, and the full results were going to be revealed at the talk at Ekoparty on September 21. Funnily enough, the details that were revealed themselves “leaked” and were sufficient for the experts to understand what is going on: On StackExchange, Thomas Pornin speculated that it was about compression. An academic paper from 2002 (PDF) was revealed. A proof of concept was submitted by xorninja, and improved by Krzysztof Kotowicz. Dan Goodin wrote a great summary of what was known at the time, and included a video of the demonstration. Finally, Threat Post published a confirmation from Juliano and Thai that was indeed compression.