A Chaos Based Image Encryption Scheme Using Digit-Level Permutation and Block Diffusion

Image encryption can be classified into pixel-level and bit-level according to the smallest processing element in the permutation and diffusion. Most pixel-level permutations only change the pixel positions, so the histograms of the permuted image and the original image are identical. The bit-level permutation can change the histogram of the image, but it is comparatively time-consuming due to bit-level computing. In this paper, we propose a new digit-level permutation. The pixel matrix of an image is decomposed into three digital matrices, and then these digital matrices are shuffled by the Henon map. This digit-level permutation combines the merits of pixel-level permutation with that of bit-level permutation. Besides, we also design a high-speed diffusion operation which exactly solves the problem that CBC-like diffusion has low efficiency. Simulations have been carried out and analyzed in detail, proving the superior security and high efficiency of our image cryptosystem.