| 摘要 |
A system creates an encrypted backup copy of the compressed audio data downloaded onto a portable audio player. When a user loads a portable audio player with audio data from a CD inserted into a computer's CD-ROM drive, the system creates an encrypted copy of the compressed audio data and stores the encrypted copy on the computer's hard disk. The encrypted copy cannot be used without a cryptographic key, but the system discards the cryptographic key once the encrypted copy of the audio data is stored. To extract usable audio data from the encrypted backup copy, it is necessary to re-insert the original CD and regenerate the cryptographic key. Once the cryptographic key is regenerated, the encrypted audio data can be decrypted and re-loaded onto the portable audio player.
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