How To Really Stop Casual Movie Disc Ripping

2010.01.09   prev     next

IF you read my prior article on DVD encryption, you probably think that protecting movies on disc from illegal ripping is impossible. And I thought so too, until just the other day. Here’s my plan for how to protect movies on disc from casual ripping by the typical consumer.

1. Develop a decryption chip that is very highly optimized for the encryption system you’re using. (Perhaps select your encryption system accordingly.) This chip may be massively parallel, or something like that, but the key feature is that it can decrypt this data at least ten times, maybe more like a hundred times, as fast as can be implemented in software on today’s consumer computer processors. (The decryption algorithm probably should be chosen to ensure that using OpenCL won’t help either.) When this chip is mass-produced in all movie players and computer drives, it shouldn’t add much to the cost of the player/drive.
2. Ensure that the decryption chip is wired into computer drives so that it can be used only by DVD-player-style playback — it cannot be employed by an app on the computer.
3. Encrypt your movie discs with a high enough number of encryption iterations so that your super-efficient decryption chip is just barely good enough to decrypt the movie during real-time playback.
4. Although it’s not strictly necessary, go ahead and keep the decryption keys (and maybe the encryption-decryption algorithm too) as secret as you can.

That’s it! Now, even if someone writes a ripping program, it will be between ten and a hundred times slower than movie playback. That means that a two-hour movie will take between twenty hours and two hundred hours (over eight days) to rip, and will massively hog your computer’s processor that entire time. So casual ripping by the typical computer owner (who doesn’t have any hacked hardware) will be extremely impractical.

Of course, as processors get faster and faster over the years, they will eventually catch up. But by that time, you can come out with a new disc format and a new decryption chip.

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