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DVD-Audio Encryption Hacked... Sort Of

by July 05, 2005

You knew it was bound to happen to DVD-Audio/MLP eventually... after quite a bit of time both the media key and the Content Protection for Pre-recorded Media (CPPM) have been compromised. This has sent the music industry for a loop, but in general, the news that high-resolution DVD-Audio content can be ripped should not be a surprise and there are plenty of reasons why this isn't necessarily cause for the industry to go back to the drawing board.

Three utilities in particular can be used to take advantage of the hack: DVD-A Explorer which breaks apart the DVD-Audio track structure to make it viewable, DVD-A Ripper which can decrypt CPPM protected AOB and VOB files, and PPCM Ripper which converts PCM (MLP) files to .WAV files.

The WinDVD player decodes the format for playback as a natural part of its function, much like the CSS encryption is decoded by DVD-Video applications during playback. What the hacks do is essentially use these decoders to grab and ultimately convert the files into usable, sharable formats. The one thing they cannot crack is DVD-Audio's Verance digital watermarking, a DRM copyright protection algorithm built right into the audio signal itself. Since the Verance watermark contains a series of identifiers which show up every fifteen seconds (plus another separate identifier every thirty seconds) if a DVD-Audio player detects that a ripped DVD-Audio disc is burnt to a blank DVD-R disc, the machine will halt playback after thirty seconds.

While the WinDVD hack bypasses two layers of DVD-Audio encryption (one used to authenticate the player and one for content encryption) it leaves the resulting audio files unable to be re-written as DVD-Audio discs without a player flagging the content... unless of course the player were hacked as well. Don't expect any actual hardware players to be "hackable" this is likely to remain strictly a software-only function.

With that in mind, one important aspect of CPPM is that it allows for a "hacked" playback device to be revoked using a Media Key Block (MKB). Each licensed player - in this case WinDVD - has assigned to it a set of unique keys that allow it to obtain the Media Key (which is then used to encrypt the audio content) from the MKB and decrypt the audio content. As WinDVD is now compromised in its current form, future DVD-Audio releases could be prevented from playing back on the software. As for the thousands of DVD-Audio titles already released, they can all be copied and ripped using the DVD-A Ripper, PPCM Ripper and DVD-A Explorer applications.

The applications were created some time ago, but it is only recently that they been made available for mass-download and use with media possessing DVD-Audio content.

We are not advocating the use of these programs here at Audioholics and will not go out of our way to post links to the applications themselves, however it is important in the grand scheme of things to be kept aware of just how well (or not) DRM is working and when major compromises are made. If anything, it sheds some light into just hgow fragile the whole concept of Digital Rights management is and the many issues that have to be overcome in order to attain true protection for intellectual property.

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About the author:
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Clint Deboer was terminated from Audioholics for misconduct on April 4th, 2014. He no longer represents Audioholics in any fashion.

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