A computer hacker claims to have broken the AACS (Advanced Access Content System) encryption specification used to control unauthorized copying on HD-DVD and Blu-ray video players.

The hacker, who goes by the name of Muslix64, said he wrote the software earlier this month after hardware compatibility problems made it impossible for him to play HD-DVDs on an X-Box that was connected to his PC.

"I started to get mad," he wrote in a posting to the Doom9.org discussion forum. "This is now what we call 'fair use'! So I decide to decrypt that movie."

Mulix64 has posted a video purporting to show the software decrypting a copy of Stanley Kubrick's 1987 film, Full Metal Jacket.

This development is a black eye for the new optical disc formats, which are both jockeying to be successor to the DVD. The Advanced Access Content System Licensing Administrator, the group that sets the AACS specification, could not be reached for comment Friday.

Seven years ago, a 16-year-old Norwegian named Jon Johansen performed a similar feat, cracking the CSS (content scrambling system) encryption scheme used by DVDs. Johansen was eventually acquitted on charges relating to the release of his decrypting software.

By cracking AACS, Muslix64 may have violated the U.S. Digital Millennium Copyright Act, which prohibits users from circumventing copy-protection tools without the permission of the copyright holder, said Fred von Lohmann, senior staff attorney with the Electronic Frontier Foundation.

Still, the software seems to have been written out of a legitimate sense of frustration with onerous copy-protection mechanisms, von Lohmann said. "He went out and bought a fancy new product that he thought would improve his experience and despite the fact that he's a legitimate buyer, it didn't work."

"When American consumers go and buy movies legitimately in the store, they should be entitled to play them back on whatever they'd like," he said. "Unfortunately that's not the set of rules that Hollywood seems to be embracing."

The IDG News Service is a Network World affiliate.