Abstract: In this paper, the defense mechanism of differential power analysis attacks on the RSA cipher algorithm is discussed.Based on analyses of self-randomized modular exponentiation algorithm, a new side-channel atomic strict self-randomized modular exponentiation algorithm is proposed in which a BBS random number generator and the side-channel atomic technology are applied to improve the original algorithm.The results of simulation experiments indicate that this method is effective and practical to prevent differential power analysis attacks.