security detectors so as to minimize power consumption in a communication interval and sequentially enables them referring to fig3 and 4 again the power controller 180 sets circuit blocks related to the data processes in the non communication interval in a normal state for example if the data received from the external devices and stored in the ram 140 is encoded and stored in the ram 140 again the cpu 120 the ram 140 and the encoder 150 are set as a normal state circuit blocks which should be always in an operational state but do not affect the operations even if they are temporarily disabled such as a security detection circuit 170 are set in a power saving state the circuit blocks set in a power saving state are preferably enabled in a sequential manner if the other circuit blocks except the security detection circuits 170 and the circuit blocks required for the current operations are set in a power saving state the power consumption in the non communication interval of the smart card 100 is further decreased fig5 is a block diagram illustrating configurations of the power controller 180 and the security detection circuit 170 in accordance with a.