DVD audio encryption scheme defeated
By Ken Fisher | Published: July 06, 2005 - 08:47PM CT

We all know that encryption and DRM are the keys to a secure future, because they work flawlessly and keep away the miscreants. Or, not. Copy Protection for Pre-Recorded Media (CPPM for short) has been cracked. Following on the heels of the famous cracking of CSS, which is used to encrypt and region encode DVDs, the industry moved to CPPM for securing audio on DVD audio discs. And, as we have all come to expect, someone has found a workaround.

Defeating the encryption requires patching InterVideo’s WinDVD versions 5, 6, or 7, which then allows a user to direct audio data directly to unprotected .WAV files. The crack involves using the application's built-in DVD audio decryption support (you've got to decrypt it sooner or later), but it changes output to allow for storing the data stream in a recognizable format. That said, the crack isn't entirely complete.

The only caveat is that DVD-Audio’s Verance digital watermarking, embedded in the audio signal itself, cannot be removed. The Verance watermark contains seventy-two bits of data comprising four CCI (copy control information) bits and eight usage identifier bits every fifteen seconds plus sixty content identifier bits every thirty seconds – if a DVD-Audio player detects that an embedded watermark does not match that of a specific disc (in other words if ripped DVD-Audio content is burnt to a blank DVD-R disc using an authoring program such as DiscWelder BRONZE), the machine will halt playback after thirty seconds.


CPPM is a bit more robust than previous solutions, and future content protected by CPPM could have the playability by InterVideo’s WinDVD versions 5, 6 or 7 revoked, making the hack no longer usable. That said, all of the content released so far has been cracked, and we can expect to see further cracks in the future.