|
|
|
|
||
Re: HD-DVD stable doors wide open, for real.You've probably heard of HD-DVD and Bluray, the high-definition video formats supposed to take over after regular "DVD". DVDs were protected using something called "CSS", or Content Scrambling System. In hindsight, a particularly pathetic "DRM" system developed, or supervised, by people with no cryptographic background. Now, for their follow up, the industry learned from most of their mistakes, and the new protection system used on HD-DVD is called AACS for "Advanced Access Content System". The specifications are open and available at www.aacsla.com and make an interesting read (if you're into that sort of thing). AACS builds on encryption and hash functions built using AES primitives (and SHA and ECC), so the foundation is sound. Basically a disc is protected with a "Title Key" that is on the disc (actually, there are many, for revokation purposes), but encrypted. To decrypt it, you need to derive a "Media Key", you get the Media Key by successfully processing the MKB (see below). On this as added a revocation system for both player hardware ("Drive") and software ("Host"), and system whereby Drives and Hosts authenticate each other, and refuse to work if the other isn't "authentic". Authentications happens using digital signatures based on an elliptic curve (If the private AACS-LA key is ever cracked, the system is _totally_ broken) All HD-DVD discs contain a "Media Key Block" (MKB), which is a sort of directory containing different sets of data. Of particular importance to the integrity of the content protection system, is the Host Revocation List and Drive Revocation List. When a disc is injected into a drive, the drive firmware will update its HRL if the one on the disc is newer. So the drive hardware may now stop talking to the software host (say your computer) if for instance your software is "WinDVD v5.3" or whatever, because that version was known to have been "cracked" to leak HD-DVD cryptographic keys in the past. Similarly, the Host will get passed from the drive the DRL and updates its copy if the one it got is newer, and thus may refuse to talk to your drive if for instance the AACS-LA has found that the drive is insecure. This is all very spiffy, especially the advanced "Subset Difference Tree" which powers the revocations in HD-DVD, but there's just one little tiny problem: Your computer isn't "trusted". By searching the process memory of your Windows software based HD-DVD player, you can locate Title Keys. Sure, players like PowerDVD and WinDVD are supposed to treat all these keys with the outmost respect, but there's only so much you can do when the computer isn't in complete DRM-from-the-BIOS-up lockdown mode. When you have Title Keys you can decrypt HD-DVD content, display it on unsecure platforms or even pass it around the world on the internet. Some weeks ago an individual posted on the internet a java program called "HDDVDBackup". This software implements the cryptographic routines needed to decrypt HDDVD-discs, but it didn't come with any of the Holy Keys. However, extraction keys from software players isn't something new and novel, so everyone knew it would just be a matter of time. Now some of those keys have been independently located and posted on the internet. Low tier Release Groups are probably preparing HD-DVD releases of movies as we speak (I believe the rest have already done this themselves weeks if not months ago, it's requires a merely competent reverse-engineer, and the top-level groups have guys way way beyond that) The interesting thing to watch now is the fallout of this totally expected event. HD-DVD might gain market share! But most interesting will be to see how that fancy revocation system works out in the wild. So basically, what has just happend is a small break in the content protection of HD-DVD. My prediction is that while it might plugged by blacklisting the software player in question, the fact is that they either tolerate key leaks from software players, or revoke them all and never again certify one. They will leak. |
return to message board, top of board |
Msg # | Subject | Author | Recs | Date Posted |
17492 | Re: HD-DVD stable doors wide open, for real. | verygoodbear | 1 | 1/13/2007 11:23:25 AM |
17504 | Re: HD-DVD stable doors wide open, for real. | paulshirley2006 | 3 | 1/13/2007 3:21:13 PM |