Abstract: A semiconductor device comprises a DSP (Digital Signal Processor), a CPU for controlling the DSP and an interface circuit. The interface circuit comprises an input circuit, a gain-adjusting circuit and an output circuit. The input circuit inputs a digital signal and supplies the signal to the DSP synchronously with a first clock signal. The gain-adjusting circuit is capable of adjusting the gain of the digital signal supplied to the input circuit. The output circuit adds a digital signal received from the DSP to the digital signal with the gain thereof adjusted and outputs a signal obtained as a result of the addition synchronously with the first clock signal. A signal path extended from the input circuit through the gain-adjusting circuit to the output circuit forms hardware. A digital signal to be transmitted propagates through the hardware to be subjected to the so-called side-tone processing.

Abstract: To provide a secure cryptographic device such as an IC card which can endure TA (Timing Attack), DPA (Differential Power Analysis), SPA (Simple Power Analysis), or the like as an attaching method of presuming secret information held therein, when the secret information held in the card or another information which is used in the secret information or an arithmetic operation using such secret information when such an arithmetic operation is performed is shown by a plurality of expressing methods and the arithmetic operation is performed, thereby making an arithmetic operation processing method different each time the arithmetic operation is performed and making each of an arithmetic operation time, an intensity of a generated electromagnetic wave, and a current consumption different.