Basically the key was discovered by the same means as the volume keys are extracted -- by dumping memory at key points while playing back a HD DVD movie using a software player. Arnezami didn't specify which player he used (or abused) for the hack, but there aren't too many around to choose from really. Frankly it doesn't matter which player is to "blame", because all software players need to store the decryption keys in memory at some point of the execution.
With the processing key out in the open, it shouldn't take too long before tools taking advantage of it become available. One can only hope that the move to High Definition formats isn't hindered too much by this latest vulnerability in the "unbreakable" AACS DRM. AACS-LA can always implement a new processing key, as well as revoke the device keys for current software based HD players (ie. WinDVD and PowerDVD), and have the software manufacturers do a better job at implementing AACS securely. But that will always take time, and there will always be hackers that outwit the software engineers.
Thanks to Pop_Smith and Gidgid for the news submission!
Sources:
Doom9 forums
Engadget HD
Written by: Jari Ketola @ 13 Feb 2007 13:16