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AACS loses the keys to its house, quickly changes locks

Efforts that began in December 2006 and continued through February 2007 lead to the discovery of the Processing Key used to encrypt high-definition media with the Advanced Access Content System. The work of a small hacking community created essentially a silver bullet that was able to defeat the copy protection of all HD DVD and Blu-ray Disc media on the market at that time.

The Advanced Access Content System Licensing Administration (AACS LA) acknowledged the effectiveness of the hack and began to enact measures to restore the integrity of its technology. Beginning May 22, which is most notably the release date of the Matrix trilogy on HD DVD, all high-definition titles shipped with Media Key Block (MKB) v3 – a new encryption key version that would render the previously discovered Processing Key obsolete.

Interestingly enough, the AACS’ updated protection measures appeared to be defeated by SlySoft, makers of AnyDVD HD software, before the new MKB versions officially hit streets. The AACS has yet to officially issue a statement and is current investigating the latest attack on the system, according to comments made by Richard E. Doherty, director of technology strategy at Microsoft, who is also actively involved with the AACS.

The initial method used by hackers to snoop the sensitive encryption keys from HD DVD and Blu-ray were accomplished using PC software. More specifically, hackers took advantage of holes in WinDVD to read data straight from the PC’s memory. While such a hack may not have been possible without the existence of software players, the AACS appears unshaken about high-def media on computers.

“Just to clarify, the original attack was on certain software players that proved to be vulnerable, and did not and does not represent a widespread break in the AACS ecosystem ... In the past PC's have typically been a big target for hacking activities, as they are designed to run arbitrary software programs. But the line between PCs and traditional CE devices is clearly blurring – and many of the best PVR systems (in my opinion) are highly customizable and capable of running user-designed software,” explained Doherty, also pointing to how a Windows Media Center box could be strong addition to home theatres.

“Keep in mind, however, that AACS is aware of the history and attack vectors of PC playback systems, and there are several technical measures (such as KCD and the entire proactive renewal system) that are designed specifically to address the particular issues of PC-based protection,” Doherty added.

The uncovering of the Processing Key to HD DVD and Blu-ray happened in February, leaving some to wonder why it wasn’t until months later until the appearance for a new MKB. Doherty provides the answer, “AACS of course has the technical means to revoke overnight. But the current license agreement generally provides for 90 days. This is to allow time for the manufacturer to repair the product and presumably fix the vulnerability, and time to rollout the patches to the affected users.”

The apparent grace period is done in the interest of consumers, as if the key were revoked immediately, legitimate consumers could find themselves with an unplayable disc until a software update. Despite the quick ‘rehack’ of the AACS, the system is designed to avoid another complete defeat like CSS – the technology used to protect DVD.

“You have seen a revocation cycle occur which has required upgrades to certain software players to make them more robust to known styles of attack. The AACS system was designed to deal with these sorts of attacks, and remains intact as a technology. This is in contrast to CSS, which is vulnerable to direct, brute-force attacks,” said Doherty, who then explains it in even simpler terms. “The analogy we sometimes give is: if you lock your house, but leave the keys lying on the street, then there's really nothing wrong with the locks or with the concept of locks in general. If you don't find the keys, you can change the locks if you like.”

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RE: Analogy
By therealnickdanger on 6/1/2007 10:34:13 AM , Rating: 2
The only problem with the analogy is that the new "locks" are all made from the same weak, breakable "material". Change the locks all you like, it won't change anything...

RE: Analogy
By BMFPitt on 6/1/2007 10:47:03 AM , Rating: 5
After realizing that writing their password on a yellow sticky note on their monitor wasn't good for security, they decided to go with a blue sticky note instead.

RE: Analogy
By Kefner on 6/1/2007 10:57:32 AM , Rating: 3
Exactly, when are they going to realize this is all just a huge waste of time and resources. Whatever they come up with, there is always someone with the skills to crack it. It's just an endless cycle.

RE: Analogy
By Christopher1 on 6/1/2007 7:55:42 PM , Rating: 2
An endless cycle and a huge waste of money. I think that the entertainment companies are being frightened into using DRM by people who have an ulterior motive: namely that they get paid by the DRM companies under the table.

RE: Analogy
By nilepez on 6/3/2007 12:52:55 PM , Rating: 2
I doubt that. Copy protection has been a part of video for more than 20 years. And in the case of HD disks, they're supposed enable some sort of system that allows you to copy it to a media server and make a physical back up.

At some point, this is no longer about consumer rights and it's just about free movies, and we're getting closer to that point.

I believe in consumer rights, but it's also painfully obvious that most making noise on this issue do so because they want to get free stuff. I've alreayd seen this with the DRM free iTunes downloads. People are complaining now because there's a tag in it with their user id in it

That said, it's also clear that the media companies cannot when this game (though I suppose they might be able to win if they did whatever DirectTV does. AFAIK, their system has been secure for at least a couple of years

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