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Monday, January 29, 2007

Digital media: Copy protection

For various reasons I was musing earlier today about how you might stop casual copying of DVD's between friends, or at least make it more difficult and I came up with a simple idea.

The idea would be to encrypt copies made from the end user's machine, while leaving the originally manufactured DVD--from here on out the OEM DVD--with minimal changes, where the end user could use a flash drive to give the code de-crypting their copy to their other entertainment devices.

The encryption would come from the serial number of their video card, the serial number of their connected monitor, and the total operating time the two are connected together, so the code would change continually with time, so no two copies would have the same code.

When playing an OEM DVD the system would behave like normal, but if a copy is made, the copy would be an encrypted one where the users own machine would automatically decrypt its own copies, but for anyone else to decrypt, a flash drive would need to be used carrying the decryption code.

The decryption would occur fully at the monitor, with possibly partial decryption at the video card, so one problem with this idea is it needs smarter monitors.

Using the flash drive to give the code would be a one-time operation on the user's own equipment meaning that they would only have to give the decryption code once, for their own copies, even though each encrypted disk would vary with its personal encryption based on the time stamp.

So end users could still give copies to friends--with a flash drive and the code--so what's the point?

The copies would be encrypted with the copying user's video card and monitor serial numbers along with a time and date stamp. And now it's a two step process: DVD and flash drive.

If an open standard were used industry wide between video card manufacturers, monitor manufacturers, and DVD manufacturers, there would be a closed loop blocking normal users from breaking the system--they'd have to go to bootleggers versus their friends.

They could still make personal copies, but would know that if those copies were given away, the information about who made the copy would be encrypted with them.

Manufacturers would stamp their own DVD's with a manufacturer's code, which of course could be copied by bootleggers, but it'd be a deliberate action with no denial about the purpose. DVD's not coded with a manufacturer's code wouldn't play on industry standard systems.

DVD copies could be copied again, with a continual coding stamp, or no more copies might be made from friend copies.

The idea here is open source in that I don't care who uses it for what purposes and it is completely open as I don't care about commercial uses. But hey, it's just something I thought up this morning while thinking about people casually handing out copies of DVD's.

It could be used with other digital media if it's a good idea. I have other ideas along this line that could be used to completely close the loop which involve the continually changing code found by the operating connection time between devices.

Are these ideas useful? I don't know. They seem simple enough, but there'd have to be a lot of coordination between manufacturers of the various devices, while end users wouldn't see any change if they didn't copy, and minimal changes if they did--once USB ports are standard on entertainment devices so using the flash card isn't a big deal.

And just knowing that you're putting your stamp on your copies could end quite a bit of casual copying and handing off to friends or just about anybody.

Sure there would be people who would just go for the OEM DVD's and make copies from those, but those are the dedicated people anyway.


James Harris
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