Cryptanalysis and security improvement for a symmetric color image encryption algorithm

This paper presents the weaknesses in the cryptosystem proposed by W. Zhang and his colleagues. The proposed method to restore the permutation rule is based on the chosen-ciphertext attack. The method is successful in restoration of the permutation rule in the case of multiple encryption rounds without any knowledge about the cryptosystem. In order to improve the security of W. Zhang's cryptosystem, the proposed modifications are made to the equations to resist against the chosen-ciphertext attack. The specific examples will demonstrate the cryptanalysis and the security improvement.