| 摘要 |
Disclosed is a digital work protection system enabling a content distributor to flexibly define usage patterns of content permitted for users. The system is composed of a recording device and a playback device. The recording device acquires a digital work, range information showing a permission range within which the digital work is permitted to be used, and a subrange key for each subrange, generates an encryption key using all the acquired subrange keys, encrypts the digital work based on the encryption key to generate encryption information, and writes the encryption information and the range information to a recording medium. The playback device reads the range information and the encrypted information from the recording medium, acquires a subrange key for each subrange, generates a decryption key using all the acquired subrange keys, decrypts the encrypted information based on the decryption key to generate a digital work, and plays the digital work.
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