Breaking an image encryption algorithm based on the new substitution stage with chaotic functions

This paper is a cryptanalysis of a recent proposed image encryption algorithm based on chaotic functions. The cryptosystem is composed of two-stage permutation and one-stage substitution for encryption of the gray scale plain-image. However, by applying chosen plaintext attack which is described in this paper, we show that all the secret parameters can be revealed. In addition, some other security defects of the cryptosystem are also highlighted. Both mathematical analysis and experimental results confirm the feasibility of this attack. As a result, the cryptosystem in this structure cannot be recommended when we need a higher level of security.