| 摘要 |
PROBLEM TO BE SOLVED: To provide an unauthorized operation detecting circuit, a device with an unauthorized operation detecting circuit, and an unauthorized operation detecting method for improving tamper resistance with respect to a packaging attack.SOLUTION: According to a plurality of change condition rules, a state value generating circuit generates a state value after a state transition with respect to a present state value, and a state value after the state transition generated according to any arbitrary one change condition rule and the arbitrary one change condition rule are selected and outputted from a selecting section based on a random number. Based on computation starting input, the present state value is stored in a state value storage section and the state value after the state transition selected and outputted from the selecting section is stored. Based on input/output of the state value storage section, the state value after the state transition is compared with the present state value by a state value comparator circuit. If the state transition is not according to the arbitrary one change condition rule, unauthorized operation is detected and a detecting signal is outputted. The plurality of change condition rules are configured to be different from one another and to use a value change with the same number of fixed bits. |
