Patent ID: 7082197

Claim:
A program distribution system for distributing a program consisting of a plurality of data elements, said program distribution system comprising: a subscriber management system for managing subscribers' subscriptions for each program or data element; a subscriber authorization system for generating a scramble key to be used for descrambling said data elements contained in said program for each of said data elements; and a multiplexer system comprising: an encoding system for encoding each of said data elements contained in said program to generate encoded streams consisting of encoded data elements for each program; a multiplexing means for multiplexing said encoded streams generated for each program by said encoding system; and a scramble means for selectively scrambling each of said encoded data elements contained in said multiplexed stream based on said scramble key generated by said subscriber authorization system, wherein said subscriber management system generates a work key for enciphering said scramble key, wherein said subscriber authorization system comprises a first encryption means for enciphering said work key supplied as EMM data in accordance with a predetermined algorithm that adopts a block encryption technique using a master key to provide an enciphered work key as an output, wherein said multiplexer system comprises a second encryption means for enciphering said scramble key contained in ECM data with said work key to provide an enciphered scramble key as an output, and wherein said work key used by said second encryption means for enciphering said scramble key is not said enciphered work key contained in said EMM data but an unenciphered work key obtained form a work key table supplied by said subscriber authorization system.