Data multiplexing device, program distribution system, program transmission system, pay broadcast system, program transmission method, conditional access system, and data reception device

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.