Patent ID: 6118873
Filing Date: 2000-09-12
Classification: G11B,H04L,H04N

Abstract:
A system for encrypting one or more broadcast programs, comprising:plural user devices, each device including plural computer-usable device keys selected from a set of device keys;at least one session key block generator for encrypting plural session numbers with the set of device keys to render a session key block, at least one of the session numbers being a dummy number when it is determined that at least one of the devices is a compromised device defining compromised device keys, the dummy number being encrypted by at least one compromised device key, the session key block being transmitted for use in decrypting the program; anda decryption module accessible to each user device and accessing the device keys of the device to determine a session key based on the session key block and the respective device keys of the device, the session key being usable by a user device to decrypt the program unless the device uses the dummy number to generate the session key.