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As any major college dude will tell you, the file-sharing genie can never be put back into the digital audio bottle. But that hasn't stopped the music business from pursuing its scorched-market policy while simultaneously applying various use-restriction technologies to every digital audio format in sight.

Quit while you are only slightly behind, say four researchers from Microsoft who recently weighed in with their provocative analysis: The Darknet and the Future of Content Distribution. The paper defines the "darknet" as a collection of networks and technologies used to share digital content, such as peer-to-peer file sharing, CD and DVD copying, and key or password sharing on email and newsgroups.

Pointing out that "people have always copied things," the researchers are particularly critical of watermarking, stating that "watermarking approaches are technically flawed and unlikely to have any material impact on the darknet." Watermarking and its audible (even if subtle) and restrictive effects have become central to audiophile concerns about the SACD and DVD-Audio formats. However, the paper asserts, "There are several reasons why it appears unlikely that such systems will ever become an effective anti-piracy technology."

For one thing, say the authors, if watermarking is not deployed everywhere, then consumers are likely to shun devices and formats that include it. But even if watermarking becomes widespread (à la the Hollings Bill), "this approach is likely to fail due to a variety of technical inadequacies." First, say the researchers, "We are not aware of systems for which simple data transformations cannot strip the mark or make it unreadable." Marks can be made more robust, says the paper, "but in order to recover marks after adversarial manipulation, the reader must typically search a large phase space, and this quickly becomes untenable. In spite of the proliferation of proposed watermarking schemes, it remains doubtful whether robust embedding layers for the relevant content types can be found."

The report finds that watermarking's second problem is "unrealistic" assumptions about key management. "Most watermarking schemes require widely deployed cryptographic keys. Standard watermarking schemes are based on the normal cryptographic principles of a public algorithm and secret keys. Most schemes use a shared key between marker and detector. In practice, this means that all detectors need a private key, and, typically, share a single private key. It would be naive to assume that these keys will remain secret for long in an adversarial environment."

As the researchers note, once the key or keys are compromised, the darknet will propagate them efficiently, and the scheme collapses. "In summary, attempts to mandate content protection systems based on watermark detection at the consumer's machine suffer from commercial drawbacks and severe technical deficiencies. These schemes, which aim to provide content protection beyond digital rights management by attacking the darknet, are rendered entirely ineffective by the presence of even a moderately functional darknet."