To enable only an authorized applicant to view program contents via a retransmission provider by correctly transmitting a work key for decoding a scramble key for program contents to be retransmitted to the viewer who has contracted with the retransmission provider such as a cable television pro vider.

When a transmitter 2 generates the work key for a receiver 5b, the work key is enciphered by a master key inherent to the receiver 5b at a CAS managing device 1 and reenciphered by a key inherent to a retransmitter 4a at the transmitter 2. The retransmitter 4a decodes only the work key generated for the receiver 5b, and any work key other than the work key generated for the receiver 5b is transmitted from the retransmitter 4a in a randomized state.