| 摘要 |
PROBLEM TO BE SOLVED: To make it difficult to forge or alter a card through recording medium. SOLUTION: This method generates time data T0 that is a random number and a specific number N0 of a card 40 when a card is issued and records them on a recorder 21 outside the card 40, wherein the number N0 is a cipher data C1 with the data T0 as a key, and the data S1 and the number N0 are recorded on the card 40 and issued. At the time of using a card, the data T0 is retrieved from the recorder 21 based on the number N0 which is read from the card 40, the ciphered data is decoded by decoding the data S1 which is separately read from the card 40 with the data T0 as a key and the card is allowed to be used through collation coincidence. When the card 40 is returned, a cipher data S2 which is enciphered by a time data T1 that newly occurs is generated and recorded on the card 40 and the recorder 21. When an enciphered data is a card utilization number, alteration becomes even more difficult. |
