| 摘要 |
PURPOSE:To prevent illegal transactions due to continuous use through off-line by making the number of times of continuous use through off-line range within the number of required times uncertain. CONSTITUTION:If the frequency of continuous use through off-line is <=4 times, unconditionally transactions are established. If the frequency exceeds four, a random number generator 68 generates random numbers, and transactions through off-line are allowed with some possibility according to the value of the random numbers. The frequency of continuous use through off-line is not set to a definit number, but falls into a range of five - 18. Thus, if an IC card is illegally used through the continuous use of off-line, it fails because the frequency cannot be specified. Illegal transactions through off-line can be prevented, and safety in terms of off-line can be improved. |
