A fast image encryption algorithm based on chaotic map and lookup table

At present, a lot of image cryptosystems with permutation/diffusion architecture have been proposed. However, permutation and diffusion are considered as two separate stages, both requiring image-scanning to obtain pixel values. Moreover, because of extraction bits directly from the discrete state value of a chaotic map to generate the pseudorandom binary sequence, the quite time-consuming conversion from floating points to integers cannot be avoided in practical applications. In this paper, a novel image encryption scheme for both combining permutation-diffusion and avoiding conversion of floating-point number is proposed. Firstly, using the lookup table constructed and S-Box of AES, an efficient approach of generating the pseudorandom sequence required by diffusion is proposed. Then, the combined permutation/diffusion architecture is employed to shuffle and change the pixels. Theoretical analyses and computer simulations both confirm that the new algorithm has high security and is very fast for practical image encryption.