Cryptanalysis of a key authentication scheme based on the chinese remainder theorem and discrete logarithms

Abstract

In 2015, Kumaraswamy et al. have proposed an improvement of the key authentication scheme based on discrete logarithms. That kind of schemes has been widely studied for many years, producing many modifications and improvements designed to overcome the weaknesses detected; most of them leading to key substitution attacks and, in some cases, allowing to recover the user’s private key. The improvement proposed by Kumaraswamy et al. is based on the Chinese remainder theorem in combination with the discrete logarithm. In this paper, several mathematical inconsistencies are revealed in the definition. Once fixed, a key substitution attack is performed.