The security of He and Kiesler's signature schemes

Abstract

He and Kiesler (1994) proposed two modified schemes to enhance the security of El Gamal's signature scheme (1985). They claimed to have remedied two technical problems of El Gamal's signature scheme, and the security of the second scheme is based on the difficulty of solving both factoring and discrete logarithms simultaneously. The paper shows that both modified schemes, in fact, do not solve the first technical problem. Besides, if one has the ability to solve the discrete logarithms, one can break the second modified signature scheme.