What exactly does BackupHDDVD do? Oh, and version 1.0 is released.

We know that AACS, the DRM shared by HD DVD and Blu-ray, is touted as being practically unbreakable and impenetrable -- much like its predecessor CSS (and we all know how well that went). Last week we saw the launch of BackupHDDVD the first tool claiming to break down AACS, but a lot of people were left wondering -- us included -- exactly what does it do? Does BackupHDDVD really actually crack AACS? Well, yes and no. With the release of version 1 of the app today, muslix64, the app's author, helped out by shedding a bit of light about exactly how this thing works. (We'll assume you know a bit about public key crypto -- if not, see here, here, and here.) One of the tenets to advanced crypto and this particular DRM system is key revocation, which for AACS means that as soon as a content publisher or industry group gets wind of some funny business, they can revoke crypto keys and push an update down the line that basically invalidates whole groups of pirated movies, hacked hardware, player software, etc.

In simple terms (ok, not that simple), muslix64 does not claim to have cracked the AACS DRM itself, but instead to expose and use each disc's hard-coded private key in order to make the hardware device run through its routine decryption process. By doing so, BackupHDDVD effectively bypasses the key revocation system which might otherwise prevent it (or your HD DVD hardware, like an Xbox 360 HD DVD drive) from being mass-invalidated as soon as the RIAA blinks. The trick here, however, is the private key extraction -- no one really knows how muslix64 exposed and extracted the private keys on the HD DVD discs needed to strip the DRM from the HD DVD discs. S/he claims it can be done with any poorly built software or hardware as the private disc keys are held in memory, but we still don't have specifics. So while we're sure to see master key lists for HD DVDs popping up on file networks in the near future, we're still hazy about how a regular user can extract his or her own keys for their own fair use purposes. We'll be sure to keep you up to date on this, though, as more information becomes available.

[(Unverified) Posted Jan 3rd 2007 9:20PM]

please people, before the crazy stuff starts, RTFA BEFORE you comment. we don't need a million posts arguing about how these keys are going to be revoked, etc.

[DaveBG Posted Jan 4th 2007 3:43AM]

Bring in the torrents!!! :)

[(Unverified) Posted Jan 4th 2007 4:47AM]

Maybe the author of the article should read a bit about private key crypto and about AACS before posting such nonsense.

Now AACS discs have a "hard-coded private key"? Gimme a break and learn about cryptography.

And those who say "They can't revoke shit because only the title keys or volume keys or 'master keys' will be published" should maybe stop talking out of their ####, should read the AACS docs at aacsla.com and learn about sequence keys and traitor tracing.

It's incredible all the nonsense that it said since BackupHDDVD has been released. And btw, this software does NOTHING to break AACS, everything in backupHDDVD is publicly available on aacsla.com.

[(Unverified) Posted Jan 4th 2007 7:12AM]

you should cite specific books, versions, and page numbers. as of
common spec book 0.91, HD DVD and DVD book 0.912, and prerecorded
spec book 0.91, there is no mention of "traitor tracing". also,
sequence keys are optional, and, even when used, the volume key
method currently implemented for current decryption (seems to me) to
bypass any way of using the sequence key against decrypters.

[(Unverified) Posted Jan 4th 2007 10:36AM]

Matt,

You can probably find good information here:

http://securityevaluators.com/eval/spdc_aacs_2005.pdf

As far as I know, the sequence keys have no other purpose than traitor tracing.

I believe that the volume keys won't be enough once the sequence keys are in use.

[(Unverified) Posted Jan 4th 2007 3:57PM]

I prefer not to go by documents not from the AACS people themselves - especially when said document is over a year old and came out before HD DVDs were ever made.

[(Unverified) Posted Jan 5th 2007 6:50AM]

So Matt, if I understand you correctly, you will not go by a well-known, well-written document by respected security experts, but you will be glad to believe some wild claims and a youtube video by an anonymous hacker.

May I add that since the document is old and as far as I remember was backed by the AACS LA, it means that some of the recommendations it makes may have been implemented in the latest versions of AACS. This makes this document totally relevant to the case.

Please crawl back to your hole.