A poster named arnezami on the Doom9 forums has claimed to have found a method of extracting the Volume ID signatures from both HD DVD and Blu-ray discs, which could make it easier for hackers to extract an unprotected version of the high-resolution video and audio content from store-bought titles.
The previous method, developed by other Doom9 members jokin and Muslix64, used a technique that scanned memory locations used by the software player WinDVD while a disc was playing, and from there extracted the Volume Unique Key for that particular disc. This method was somewhat cumbersome, and required some sophistication on behalf of the cracker. Furthermore, it had to be repeated for each HD DVD or Blu-ray title. arnezami used a program called USB sniffer to connect to an HD DVD drive as a mass storage device, started playing back the movie, then scanned the resulting dump of the transfer between the drive and the computer.
As shown in the chart below, the "MKB" is the Master Key Block, which is different for every disc. When combined with the device key for a particular player, this generates a Master Key (Km). This key is then combined using the AES algorithm to create the Volume Unique Key (Kvu). It was this Volume Unique Key that Muslix64 captured in memory from WinDVD. The Volume Unique Key is then combined with an encrypted Title Key stored on the disk to create the Title Key (Kt) which is then used to decrypt the video and audio content on the disc itself.
Simplified high-def disc decryption chart
The new method saves a step and allows anyone to easily capture the Volume ID from any disc, but it still requires a Master Key in order to unlock the content. The creators of AACS, the copy protection used by HD DVD and Blu-ray, anticipated that this would happen, and built into the specification the ability to revoke Device Keys that have been released into the wild, so that new discs will refuse to work on those particular players or playback software versions.
So does this mean that the gates are open for Blu-ray and HD DVD? Not quite. The hackers believe that it is only a matter of time before WinDVD's device key is revoked, which will necessitate a software update for WinDVD owners and set the work of decrypting new titles back to square one. The hackers have been careful not to release the actual Device Key for WinDVD to the public, but as all the hacks to date have been accomplished using software-based players (which unlike hardware-based players can be easily updated over the Internet) it seems likely that these Device Keys will be revoked anyway. Therefore, it cannot really be stated that AACS has been completely cracked at this point in time. The new crack still requires a general-purpose method of extracting the Master Keys, which has not yet been accomplished.
Still, the discovery of an easy way to grab the Volume ID information from Blu-ray and HD DVD discs demonstrates that there is more than one way to skin the encrypted cat, as it were. While not a complete crack, it does open the door slightly wider towards the ability to remove protection from high-definition media.