Abstract: The paper introduced Differential Power Analysis(DPA) attack of the decrypt encrypted circuits with SMS4, it is one particularly powerful type of Side Channel Attacks (SCA). All its theories are based upon the physical characters, power consumption models and data-dependent power consumption of CMOS logic gates which form the integrated circuits (ICs).The paper introduced the design and realization of DPA attacks of SMS4. Correct secret key of encryption algorithm is cracked successfully with experiments. It comes gradually and closely into ultimate target of the attack. The result indicates that SMS4 encrypted systems without some extra protective measures can' t resist the attacks of DPA, because of the leakages from the physical signals and the difference of power consumption while processing the different data of ICs. The results can give the researchers to provide a useful reference for the safety design.

Key words: SMS4, Side channel attacks, Hamming distance, Power consumption model, Simulation platform