A novel image encryption algorithm based on LFT based S-boxes and chaos

A novel and efficient image encryption algorithm based on the chaotic system and S-boxes is introduced in this paper, in which an original S-box is produced by linear fractional transformation (LFT) on Galois field of order 256, and then a set of S-boxes are obtained by performing zigzag confusion on the original S-box. The encryption architecture of forward substitution process (FSP) and reverse substitution process (RSP) is adopted. For each pixel of the plain image, a corresponding element in a certain S-box is chosen, and the choosing process of the S-box and element depends on two random numbers, the plain image pixel and the previous cipher pixel. Moreover, 2D---LASM is used to generate the random numbers, and its initial values and system parameter are computed by the SHA 256 hash of the plain image and the given values. Therefore, the proposed scheme has highly relationship with the original image and it can resist known-plaintext and chosen-plaintext attacks. Besides, correlated chaos and correlated substitution are used to improve the security level. Experiment results and security analyses demonstrate that the proposed image encryption algorithm is secure and efficient.