May 26, 2018

Search Results for: aacs

AACS Updated, Broken Again

[Other posts in this series]

We predicted in past posts that AACS, the encryption system intended to protect HD-DVD and Blu-ray movies, would suffer a gradual meltdown from its inability to respond quickly enough to attacks. Like most DRM, AACS depends on the secrecy of encryption keys built into hardware and software players. An attacker who discovers a player’s keys can defeat the protection on any disc that works with that player. AACS was designed with a defense against such attacks: after a player has been compromised, producers can alter new discs so that they no longer work with the compromised player’s keys. Whether this defense (which we call “key blacklisting”) will do much to stop copying depends how much time elapses before each leaked key is blacklisted.

Next week marks three months after the first compromised player key appeared on the Internet (and more than five months after cracks for individual discs began to appear). Discs slated for release on Tuesday will be the first to contain an update to AACS that blacklists the leaked keys.

What took so long? One limitation comes from the licensing agreement signed with player manufacturers, which requires that they receive ninety days’ notice before their keys are blacklisted, so that they have enough time to update their products.

Customers who obtained the new discs a few days early confirmed that the previously leaked keys no longer worked. It seemed as if AACS had recovered from the attacks just as its designers intended.

However, a new twist came yesterday, when SlySoft, an Antigua-based company that sells software to defeat various forms of copy protection, updated its AnyDVD product to allow it to copy the new AACS discs. Apparently, SlySoft had extracted a key from a different player and had kept the attack a secret. They waited until all the other compromised keys were blacklisted before switching to the new one.

The AACS Licensing Authority will be able to figure out which player SlySoft cracked by examining the program, and they will eventually blacklist this new key as well. However, all discs on store shelves will remain copyable for months, since disc producers must wait another ninety days before making the change.

To be successful in the long run, AACS needs to outpace such attacks. Its backers might be able to accelerate the blacklisting cycle somewhat by revising their agreements with player manufacturers, but the logistics of mastering discs and shipping them to market mean the shortest practical turnaround time will be at least several weeks. Attackers don’t even have to wait this long before they start to crack another player. Like Slysoft, they can extract keys from several players and keep some of them secret until all publicly known keys are blacklisted. Then they can release the other keys one at a time to buy additional time.

All of this is yet more bad news for AACS.

Digg Users Revolt Over AACS Key

I wrote yesterday about efforts by AACS LA, the entity that controls the AACS copy protection system used in HD-DVD and Blu-ray discs, to stop people from republishing a sixteen-byte cryptographic key that can unlock most existing discs. Much of the action took place at Digg, a site that aggregates Web page recommendations from many people. (At Digg, you can recommend pages on the Web that you find interesting, and Digg will show you the most-recommended pages in various categories.

Digg had received a demand letter from AACS LA, asking Digg to take down links to sites containing the key. After consulting with lawyers, Digg complied, and Digg’s administrators started canceling entries on the site.

Then Digg’s users revolted. As word got around about what Digg was doing, users launched a deluge of submissions to Digg, all mentioning or linking to the key. Digg’s administrators tried to keep up, but submissions showed up faster than the administrators could cancel them. For a while yesterday, the entire front page of Digg – the “hottest” pages according to Digg’s algorithms – consisted of links to the AACS key.

Last night, Digg capitulated to its users. Digg promised to stop removing links to the key, and Digg founder Kevin Rose even posted the key to the site himself. Rose wrote on Digg’s official blog,

In building and shaping the site I’ve always tried to stay as hands on as possible. We’ve always given site moderation (digging/burying) power to the community. Occasionally we step in to remove stories that violate our terms of use (eg. linking to pornography, illegal downloads, racial hate sites, etc.). So today was a difficult day for us. We had to decide whether to remove stories containing a single code based on a cease and desist declaration. We had to make a call, and in our desire to avoid a scenario where Digg would be interrupted or shut down, we decided to comply and remove the stories with the code.

But now, after seeing hundreds of stories and reading thousands of comments, you’ve made it clear. You’d rather see Digg go down fighting than bow down to a bigger company. We hear you, and effective immediately we won’t delete stories or comments containing the code and will deal with whatever the consequences might be.

If we lose, then what the hell, at least we died trying.

This is a remarkable event. Critics of Web 2.0 technologies like Digg often say that users are being exploited, that the “communities” on these sites are shams and the company running the site is really in control. Here, the Digg company found that it doesn’t entirely control the Digg site – if users want something on the site badly enough, they can put it there. If Digg wasn’t going to shut down entirely (or become clogged with postings of the key), it had no choice but to acquiesce and allow links to the key. But Digg went beyond acquiescence, siding with its users against AACS LA, by posting the key itself and practically inviting a lawsuit from AACS LA.

Digg’s motive here probably has more to do with profit and market share than with truth, justice, and the American way. It’s not a coincidence that Digg’s newly discovered values coincide with the desires of its users. Still, the important fact is that users could bend Digg to their will. It turns out that the “government” of Digg’s community gets its power from the consent of the governed. Users of other Web 2.0 sites will surely take note.

AACS Plays Whack-a-Mole with Extracted Key

The people who control AACS, the copy protection technology used on HD-DVD and Blu-ray discs, are apparently trying to shut down websites that publish a certain 128-bit integer. The number is apparently a “processing key” used in AACS. Together with a suitable computer program, the key allows the decryption of video content on most existing HD-DVD and Blu-ray discs.

I won’t publish the key here but you can spot it all over the Web. It’s a long string starting with “09 F9”.

The key has been published on a few websites for months, but in recent days the AACS “Licensing Authority” (AACS LA) has taken to sending out demand letters to websites that publish the key, claiming that the key is a circumvention technology under the DMCA. News of these demand letters, and the subsequent disappearance of content and whole sites from the Net, has triggered an entirely predictable backlash, with thousands of people reposting the key to their own sites.

The key will inevitably remain available, and AACSLA are just making themselves look silly by trying to suppress it. We’ve seen this script before. The key will show up on T-shirts and in song lyrics. It will be chalked on the sidewalk outside the AACS LA office. And so on.

It’s hard to see the logic in AACS LA’s strategy here. Their end goal is (or should be) to stop unauthorized online distribution of high-def video files ripped from HD-DVD or Blu-ray discs. The files in question are enormous and cumbersome to store and distribute, containing more than a gigabyte of content. If you can’t stop distribution of these huge files, surely there’s no hope of stopping distribution of a little sixteen-byte key, or even of decryption software containing the key. Whatever tactics can stop distribution of the key should be even more effective against distribution of movies.

My guess is that AACS LA miscalculated, thinking that a few demand letters would succeed in suppressing the key. As the key spread, it seemed natural to continue sending letters – to do otherwise would be an admission of defeat. Now the key is spread so widely that there’s no point in sending any more letters.

The next question is whether AACS LA will try to sue somebody who defied a demand letter. There’s no real strategic point to such a suit, but even big organizations act out of spite sometimes.