Claims and Counterclaims in SDMI Hack Challenge

A group of researchers has claimed success at cracking four digital audio watermarking technologies presented in a challenge by the Secure Digital Music Initiative in September. The claim has been denied by David Leibowitz, chairman of Verance Corporation, creator of one of the challenged watermarks. SDMI has made no public statement on the claim, and has resolved to remain silent until all 447 submitted hacks are evaluated.

Despite SDMI's reticence, several news stories have popped up supporting the contentions of computer scientist Edward Felten and his associates at Princeton, Rice University, and Xerox Palo Alto Research Center (PARC). The hackers have created a website where they promise to reveal the details of their work within two weeks. Their most significant claim is that they succeeded in removing the watermarks without damaging the quality of the music. (How music quality is determined isn't apparent from any documents made public by either SDMI or Felton's group, although both allude to "subjective evaluation.") The researchers say their work is replicable and that any clever hacker could easily devise methods to remove watermarks.

"We have attacks that quantitatively don't damage the music files' audio quality more than the watermarking schemes themselves," said Scott Craver, a Princeton graduate student, one of the researchers and an expert in cryptography. Craver said the ultimate criterion for watermarking is "whether the sound quality is good enough for the common pirate. If you subject a music file to a modification whose quality degradation would bother a recording engineer but would not bother most of the people who download MP3s, that would be a problem." Craver pointed out that his group's effort isn't intended as an attack on the music industry. "We are not out to get the recording industry; if our results can help anyone develop a better security system, we're happy."

On October 25, Leibowitz refuted Felten's assertion. "I can't explain the discrepancy concerning Professor Felten and what he claims. I have no way of evaluating their claims other than what we've heard," he said. Verance has signed licensing agreements for the use of its technology with all of the "Big Five" of the music industry: EMI, Universal Music, Sony Music Entertainment, Bertelsmann Music Group, and Warner Music Group. Verance's watermarking technology, which survived the first round of testing and elimination by SDMI, will be used in upcoming DVD-Audio releases from Warner, as will a copy-prevention technique known as Copy Protection for Prerecorded Media (CPPM). CCPM was developed by the 4C Entity, an industry alliance of IBM, Intel, Matsushita and Toshiba.

Last year, hackers defeated an encryption technique called CSS ("content scrambling system"), causing a long delay in the launch of DVD-A. Warner's senior vice-president of technology, Jordan Rost, vows there won't be another delay. "Nothing has happened to change our plans to introduce titles in November," he told Pro Sound News. The new discs include classical titles and pop hits such as Core by the Stone Temple Pilots and Tigerlily by Natalie Merchant, and will be hitting the street as DVD-A players begin to appear in stores.