The Advanced Access Content System (AACS) has been cracked. A contributor to the Doom9 online forum has figured out how to extract the so-called Processing Key (PK) from an HD player, allowing any currently available HD DVD and Blu-ray Disc to be copied.

The trick, identified by a coder going by the handle Arnemazi, allows a Volume Unique Key (VUK) to be generated from a disc's Volume ID (VID). Usually, a player retrieves the disc's VID and uses the PK to create a VUK to decrypt the content.

Arnezami said he discovered the crack by scanning the system's memory and found the PK before it was erased after the generation of the VUK. He acquired a VID by monitoring traffic on his system's USB ports as the player software talked to an HD DVD drive.

As yet, there's no code to automate this procedure, so mass duplication of pre-recorded BDs and HD DVDs isn't yet possible, it would seem. The crack also relies on the non-random nature of the VIDs embedded in discs to date, a feature that makes them easier to find in memory and/or the USB traffic - or even to guess. New releases with random VIDs would make spotting the VID much harder, but the fixed data-structure of the VID doesn't help AACS' security.

Arnemazi's efforts come just over a month after a fellow Doom9 coder, Muslix64, discovered Title Keys for various HD DVDs in memory and used them to decrypt those discs for duplication. Backup tools for both HD DVD and BD that require the entry of these keys were published last month.