CONDITIONAL ACCESS SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a cable television system which provides conditional access to services.

SOLUTION: This cable television system includes a headend from which service "instances" or programs are broadcast and a plurality of set top units for receiving the instances and selectively decrypting the instances for display to system subscribers. The service instances are encrypted using public keys and/or private keys provided by service providers or central authorization agents. Keys used by the set tops for a selective decryption may also be public or private in nature, and such keys may be reassigned at different times to provide a cable television system in which piracy concerns are minimized.

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