Three questions about HDCP (Score 5, Insightful)

1. Why bother protecting DVI? Have any prior DRM systems been attacked through DVI?
   No, because cracking CSS was easier. And chances are the next generation will be cracked in a similar manner. I have not yet seen any DRM research suggesting otherwise. But any measure against hacking makes sense only if you make all other possible attacks equally difficult. (Why have a steel door if there is an open window?) Why the inconvenience for your customer, if you know it will have almost no positive effect?
2. About key revocation (part of HDCP afaik): What is the benefit of being able to revoke keys known to be compromised?
   Yes, you can prevent a hacked player from playing back a legally purchased copy on a unprotected device. But apparently most piracy today comes from P2P networks. How will you be able to tell which key was used to decrypt a DRM-free copy that shows up on a P2P-network? Release groups would probably just keep their cracked key secret. (Watermarks? Not robust against removal afaik.) Revocation can neither prevent spreading of content to P2P, nor playback of unprotected files obtained from P2P.
3. A little revocation scenario: Company X sells 10 million HDCP-enabled devices. Someone devises a crack that theoretically compromises the key on all those devices (e.g. by finding a flaw in X's key generation). Media companies consequently block all 10 million devices. Does X have to replace 10 million devices for free, or are 10 million customers stuck with a useless device?
   If you sell HDCP-enabled products, make sure that you know your cryptography very, very well. Or you might go out of bussiness soon.

Bonus question: why would I want this crap? I tend to like movies for their storytelling, and am quite happy with the quality that DVDs offer me. If this stuff ever takes of, I'll just be happily buying used DVDs from suckers who upgrade their collection to HD.