In accordance with an embodiment, the logical exclusive operation on the random number RAND and the OPc value are performed several times, the logical operation and encryption processing using a random number RAND and logical operation and encryption processing using a random number S are done in any order, which brings an increase of an attack complexity as to whether to calculate the correlation coefficient from the power consumption waveform at any point when analyzing the correlation power, whereby it is possible to defend the CPA attack effectively.