A first information processing unit stores identification information into a storage module, stores an encrypted contents signal into a mass storage unit, and supplies the encrypted contents signal and identification information to a second information processing unit through a communication section. In a receiving unit of the first information processing unit, log information generated by a purchase processing module is stored into the storage module every time the contents key is decoded, and the log information is transmitted at predetermined timing to a key management center through the transmission section. The second information processing unit receives the encrypted contents signal and the identification information through a communication section, and causes a contents processing section to decode the encrypted contents signal and to append the identification information thereto.