Security researchers at Princeton are making great strides in picking apart the systems used by copy-restriction companies to corrupt the CDs sold by music labels like Sony-BMG. Princeton's Alex Halderman has published preliminary results of his and Ed Felten's work on reverse-engineering the Digital Rights Management systems that were the subject of so much controversy when Sony was caught infecting its customers' computers with them: MediaMax from Suncomm and XCP from First4Internet.
Halderman's paper shows that these systems contain numerous implementation mistakes that would make it simple to circumvent them, once their presence was known:
The MediaMax watermark fails to satisfy the indelibility and unforgeability requirements of an ideal disc recognition system. Far from being indelible, the mark is surprisingly brittle. Most advanced designs for robust audio watermarks manipulate the audio in the frequency domain and attempt to resist removal by lossy compression, multiple conversions between digital and analog formats, and other common transformation. In contrast, the MediaMax watermark is applied in the time domain and is rendered undetectable by even minor changes to the file. An adversary without any knowledge of the watermark’s design could remove it by converting the tracks to a lossy format like MP3 and then burning them back to a CD, which can be accomplished easily with standard consumer applications. This would result in some minor loss of fidelity, but a more sophisticated adversary could prevent the mark from being detected with almost no degradation by flipping the least significant of one carefully chosen sample from each of the 30 watermark clusters, thereby preventing the mark from exhibiting the pattern required by the detector.Link Next post