evan_tech -- great series of posts on AACS

08:35 am, 18 Jan 07

great series of posts on AACS

I want to highlight a recent series of posts on AACS (the copy protection scheme used by HD-DVD and Blu-ray). They start with an overview of how the system works, describe which piece was recently cracked, and then devote some entries to the cat and mouse game between the crackers (who want to keep the authorities from knowing which software they had cracked, as the authorities can then disable that software's key in future releases) and the authorities (who have designed the system such that they can track down exactly these people -- the sixth post describes some of the design decisions they've made to facilitate this). They eventually build up to an economic model predicting the behavior of a smart attacker and what that bodes for AACS in the future.

This post is the most recent in the series, but it has links to the previous ones so you can read them in order. Good stuff.

Anonymous
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evan

Re: Interesting, but...

Totally agree that all of this is a major consumer screw-over. I'm interested in it mostly because (a) it's interesting to think about, (b) if I'll ever be able to play these movies I'm certain it will be via "illegal" means.

In post #5, he goes into your idea a bit:

Even if the attackers want to cause maximum financial harm to Hollywood (which probably isn’t their goal), their most effective strategy is to limit how many title keys they publish. One way to do this is to give Hollywood a “release window” — a kind of grace period after each disc is released, in which the title key doesn’t get published. A site could let people upload the headers of a disc; the site would then wait N days before decrypting and releasing the title key.

Interestingly, this release window strategy resembles the studios’ current approach to extracting revenue from films, in which a film is available first in the highest-revenue format — in theaters — then later in a succession of lower-revenue formats — DVD and television. The idea is to extract more revenue from the most enthusiastic fans in early stages and pick up whatever revenue is available from everyone else later.

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gaal

Re: Interesting, but...

And:

In practice, MVP [defined earlier as "Marginal Value of Protection (MVP): the revenue they would get if AACS were impossible to defeat, minus the revenue they would get if AACS had no effect at all" --GY] might be negative. AACS makes a disc less useful to honest consumers, thereby reducing consumer demand for discs, which hurts studio revenue. (For example: Alex and I can’t play our own HD-DVD discs on our computers, because the AACS rules don’t like our computers’ video cards. The only way for us to watch these discs on our equipment would be to defeat AACS. (Being researchers, we want to analyze the discs rather than watch them, but normal people would insist on watching.)) If this revenue reduction outweighs any revenue increase due to frustrating infringement, MVP will be negative. But of course if MVP is negative then a rational studio will release its discs without AACS encryption; so we will assume for analytic purposes that MVP is positive.

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jlb	Fascinating read, thank you. Even aside from the game theory bit, I hadn't read anything about AACS yet. The piracy mitigation technology built into it is pretty cool.
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