August 20th, 2007

Why watermarking is a bigger devil than DRM

Posted by George Ou @ 2:20 am

Categories: Apple, Consumer electronics, Microsoft, News, Security

Tags: Digital-rights Management, Music, George Ou

There’s been much news lately about the record industry getting ready to give up on DRM. DRM (Digital Rights Management or some call it Digital Restrictions Management) is a form of copy protection that protects the rights of content owners and restricts the usage of the customers it it’s probably one of the most hated technologies in the consumer world. That hatred doesn’t necessarily stem from a fundamental opposition to copy protection; it’s because DRM impinges on the consumer’s right to fair use. So when news came that record companies are looking at dumping DRM, consumers cheered. All it takes is a single stolen credit card buying a bunch of songs and uploading it to break the entire schemeBut we might be celebrating a bit early because the record companies are sneaking in a bigger devil in the form of watermarking. This was confirmed by Wired Listening Post.

You can say a lot of bad things about DRM, but one thing it didn’t do was ruin the quality of the content. Watermarking advocates will tell you that their technology is “inaudible” or “invisible” to the human ears or eyes, but that’s fundamentally impossible if the watermarking is to be effective. If the watermarking was truly inaudible, then it can be removed through analog filtering without affecting the quality of the image or audio. Since that would make the watermarking useless, it usually is visible or audible which means you’ve irreparably changed the content. It’s bad enough that downloaded music and video are worse than audio CDs or DVDs (even so-called HD video downloads are worse than DVD quality) because the bitrates are too low, but mucking it up with watermarking is just too much to bear.

One other potential usage of watermarking is user tracking. A. L. Friedman (writer for Contentinople) says that there will be no user tracking. That may very well be the case initially since music would have to be individually encoded for each customer, but it doesn’t rule it out in the future. Friedman noted that some of these fears are rooted in Apple’s embedding of the buyer’s name in the DRM-free music from EMI. The justification for these watermarks which are unique to each track but not unique to the user is to track which songs are being pirated on peer-to-peer networks like BitTorrent and how often they’re traded. But if that’s all they want to do, then it would be just as easy to leave the watermark out of the track and simply track the hash of the file.

Quick definition of hash: A hash is a number created by a hash function from a data file. This number is effectively a digest of the original file that can be used as a digital fingerprint for identification or integrity checking purposes. Hashes generated from quality hash functions like SHA-256 are for all intents and purposes unique. Hashes aren’t truly unique, but they’re unique enough that the odds of finding a different file that generates the same hash are astronomical. A good hash function is resilient enough that even the best crypto researchers in the world can’t find two files with the same hash.

While I don’t particularly care for DRM, I’ll put up with it like most consumers. I’m not even so sure I have a problem with my name being embedded in the music file since it doesn’t restrict me from doing legal things with my content so long as the record companies have to prove I uploaded it illegally and that it wasn’t merely a case of theft. But I definitely have a problem with my music being polluted with watermarks no matter how supposedly inaudible they are.

[Update 3:05PM - There's some debate as to whether watermarking causes perceptible noise or not and I think that misses the whole point. If it's not perceptible, then it can be stripped out and watermarking is pointless. If it is perceptible then I don't want it. But the most compelling argument against this entire watermarking scheme is that all it takes is a single stolen credit card buying a bunch of songs and uploading it to break the entire scheme. The whole scheme is pointless.]

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