| 摘要 |
PROBLEM TO BE SOLVED: To prevent use of an illegal card by forgery such as copying. SOLUTION: A recorder records fixed data in a fixed part E2 at the time of issuing a prepaid card 6 to verify, it measures a distance from an end of the card to a start position of the fixed data and a distance from a completion position of the fixed data to the end of the card, enciphers variable data with the measured value as a key and records them in a variable part E1. At the time of using the prepaid card 6, a reader/writer reads the fixed data in the fixed part E2 of the prepaid card 6, measures the distance from the end of the card to the start position of the fixed data and the distance from the completion position of the fixed data to the end of the card, decodes the enciphered variable data recorded in the variable part E1 with the measured value as the key, and updates the variable data in accordance with the amount of consumed money or the like. |
