Microsoft Patents Uncrackable DRMMicrosoft may have just succeeded in giving the lie to claims by anti-DRM advocates that tech and record companies should forget about digital-rights management because they can never come up with something that's totally immune to cracking.
That's because two inventors working in Redmond, Darko Kirovski and Henrique Malvar, have taken concepts from spread-spectrum technology--used by the military for secure radio communications--and adapted them to the task of permanently inserting the owner's (aka content producer's) name within MP3 and .WAV files.
Microsoft was awarded U.S. Patent 7,266,697, entitled "Stealthy audio watermarking," on Sept. 4, for the duo's work.
As the patent's abstract explains it: "The watermark identifies the content producer, providing a signature that is embedded in the audio signal and cannot be removed. The watermark is designed to survive all typical kinds of processing and malicious attacks."
The stuff is probably the most thorough and complicated technology ever to be applied to 99-cent music files. It's robust enough to resist all attempts to remove the watermark from the clip, including changes in time and frequency scales, pitch shifting, and cut/paste editing.
I should note that it's important to make a distinction between what Microsoft is doing here--watermarking--and what's commonly thought of as DRM, which is copy protection or encryption. Watermarking isn't encryption and it doesn't necessarily prevent unauthorized playback. On the other hand, it can serve in place of any other type of DRM, if the playback system (i.e., the MP3 player or online music store) requires the presence of the watermark before it'll let you listen to your file. (I'm putting this paragraph here in anticipation of all the "Wolfe, you don't know Jack about DRM" comments I'll probably get anyway.)
The watermarking scheme evolved by the Microsoft scientists is so robust that, if it's used properly, it can indeed serve as an uncrackable DRM scheme. Keep in mind that Kirovshi and Malvar aren't just proposing a single watermarking method. Their patent outlines three (count 'em) different ways to apply spread-spectrum to the task of locking-down audio files.
Check out this description of three-fold DRM they're doing, from the patent:
"[The] watermarking system employs chess spread-spectrum sequences to improve the balance of positive and negative chips in the watermarking sequences. . . In another implementation, a watermarking system employs an energy-level trigger to determine whether to skip encoding of a portion of a watermark within a given time span of an audio clip. . . In a [third] implementation, a watermarking system begins encoding of a watermark at a variable position after the beginning of an audio clip."
Here are a few flow charts, from the patent itself, which give a more definitive idea of how the watermarking technique works in practice. (Click on the first one to get to the image gallery, which will let you view the other five.)
Microsoft's watermarking patent diagram. (Click to see the full flowchart, and to view the rest of the Microsoft patent pictures.)Full Story At Source
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