Deciphering an RGB color image cryptosystem based on Choquet fuzzy integral

For the purpose of designing better color image cryptosystems, it is necessary to perform a mathematically rigorous security analysis for the existing ones. In this study, a Choquet fuzzy integral-based color image cryptosystem with shift-diffusion architecture is cryptanalyzed. Firstly, it is demonstrated that the color image cryptosystem is irreversible, since the encryption algorithm cannot be decrypted correctly. Meanwhile, a simple improvement is presented to guarantee the reversibility. Moreover, a cryptanalysis of the improved scheme is proposed and results show the improved color image cryptosystem can be broken by a known plain/cipher image pair. The shift-diffusion architecture should alter the external key every time for security consideration.