| 摘要 |
PROBLEM TO BE SOLVED: To disable a 3rd person to access data even when illegally obtaining a key code for data access permission by providing a 1st key code change part which updates a 1st key code each time data are accessed by a 1st prescribed quantity. SOLUTION: An IC card 10A is equipped with a key code changing circuit 20 and a host computer 11A is also equipped with a key code changing part 21 corresponding to it. This system updates the key code by the same method by the key code changing circuit 20 and key code changing part 21 each time data are accessed by the prescribed quantity, e.g. one byte through a terminal device 12 between the IC card 10A and host computer 11A so as to disable the IC card 10A to illegally be accessed. Consequently, even if a 3rd person receives the key code with a radio wave, the key code is automatically changed thereafter not through a radio wave, so the 3rd person is unable to rewrite or read the contents of the IC card 10A by using the obtained key code. |
