A method for controlling access to digital information is performed based on a plurality of decryption keys sent by the information provider. A first type of decryption key instructs a user's host system to reproduce the digital information in accordance with a first level of reproduction quality degradation. Additional keys may specify other degradation levels. The quality of the digital information may be degraded based on a time condition or a use condition. Alternatively, only a portion of the information may be made viewable by a user. In order to obtain full and unrestricted access, the user must obtain a type of decryption key from the provider which removes all previous limitations on reproduction quality degradation.

 
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< Information playback device, information recording device, information playback method, information recording method, and information recording medium and program storage medium used therewith

< Data synchronization apparatus and method

> Low I/O bandwidth method and system for implementing detection and identification of scrambling codes

> Method for providing a crypto key and checkword to an encryption device

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