DIGITAL BROADCASTING SYSTEM AND ITS DEVICE AND PROGRAM

摘要

PROBLEM TO BE SOLVED: To prevent past contract information from being illegally written and to eliminate the necessity of managing contract information by a receiving terminal after canceling the contract. SOLUTION: A transmitter transmits a broadcasting wave including both of a key information packets Pk having a key number Nk and key information and a contract information packet Pcr having contract information Dcr ciphered so as to be deciphered on the basis of the key information and a key number Nk. A receiver 20 receiving both the information packets Pk, Pcr deciphers the contract information Dcr included in the packet Pcr on the basis of the key information of the packet Pk when the key number Nk of the received packet Pk is the newest value and the key number coincides with the key number Nk of the received packet Pcr, and updates and stores the obtained contract information. Namely the contract information Dcr can be updated only by the newest key number Nk and the newest updating number Ncr.