Wen the music industry as developing a ystem to control downloading, the SDMI (Secure Digital Music Initiative) invited all varieties of hacker to try and crack the copy protection technologies that were in the pipeline for future music releases. The SDMI website publicly offered four music tracks with embedded, inaudible watermarks. The marks had to survive copying and conversion from digital to analogue and back again, but not affect the sound quality. The challenge was for anyone to send the SDMI 'oracle' website a version of the test music with the watermark successfully removed, without loss of sound quality.
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