| 摘要 |
PURPOSE:To decode privacy information by reading received revision information even when a contractor uses any storage medium before or after update and selecting automatically a key used for the time. CONSTITUTION:A specific address, a key K1 corresponding thereto, an update number R1, a key K2 and an update number R1+1 are stored in a card (a) distributed to a recipient, and a specific address, a key K2 and the update number R1+1, a key K2 and an update number R1+2 are stored in an update card (b). Even when the cards (a), (c) are used for a period P2, since a receiver reads the update number R1+1 and selects the key K2 corresponding thereto, the transmission information is correctly decoded. Since the information is received even when the recipient uses the card (c) before and after update over a long period, the operability of the recipient is much simplified and the possibility of disabled reception due to erroneous loading of the card around the period of the update is precluded. |
