HD DVD anti-rip encryption cracked

First test of AACS key-switching system

Has the HD DVD next-generation optical disc format's anti-rip technology been cracked? That's certainly what's being claimed by a programmer going by the name muslix64 who has posted a Java-based app he maintains will free the video on a disc from its encryption shackles.

HD DVD used the AACS copy-protection system to encode content. So does the Blu-ray Disc format, though it adds a couple of extra anti-piracy techniques to boost its level of protection. According to muslix64's posting on a Doom9 forum, nosing around his PC's memory, he found his test disc's title encryption key and was able to use to copy the movie to his hard drive and decrypt the video.

Enter BackupHDDVD, his Java-coded utility that gets a movie's key from memory, possibly via the player software, and then uses it to copy the movie over to the hard drive in an unencrypted form. There's a caveat: muslix64 admitted the code - for which he's provided the source - is highly unstable. It's also open to question how generic all this is as it only seems to work with one title.

The programmer added that he's also found the disc's overarching volume key, and is preparing a BackupHDDVD update for 2 January that will allow users to extract other files from an HD DVD.

Muslix64 posted his utility just before Christmas, so it's taken a little longer than usual for hackers and other users to evaluate the coder's claims. But it remains a potentially major embarrassment for the HD DVD format's supporters in the content and hardware industries, coming just ahead of a big Consumer Electronics Show (CES) push to drive the format ahead of its rival, Blu-ray Disc.

After the DVD format's more basic encryption technology, Content Scrambling System (CSS), was cracked by 'DVD Jon' Johanssen, AACS was heralded as a much bigger hurdle for hackers.

However, AACS does more than boost the complexity of the encryption. It adds techniques for ditching compromised keys, and it remains to be seen how not only the AACS organisation but also the HD DVD camp respond to this. Keys can be tweaked to force users to update their software if they want to be able to play future titles, and that may be what happens in this instance. ®

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