Patent ID: 7072471

Claim:
A program transmission method for transmitting a program consisting of a plurality of data elements, said method comprising: a scramble key generation step for generating a plurality of scramble keys to be used for scrambling a plurality of data elements contained in said program so that a subscriber can watch and/or hear only programs or data elements subscribed for by said subscriber, said scramble key being updated at predetermined intervals with a random number generator; an encoding step 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 step for multiplexing said encoded streams provided for each program by said encoding step; and a scramble step for selectively scrambling each of said encoded data elements contained in said multiplexed stream based on said generated scramble key, wherein said multiplexing step comprises an encryption step for enciphering a scramble key contained in ECM data, wherein said scramble key generation step generates a work key table which shows the correspondence between said work key and a work key identification number for identifying said work key, wherein said encryption step in said multiplexing step obtains a work key from said work key identification number contained in said ECM data by referencing said work key table, said encryption step enciphers said scramble key contained in said ECM data by using said work key obtained from said work key table, and said encryption step provides said enciphered scramble key as enciphered ECM data.