A feedback chaotic image encryption scheme based on both bit-level and pixel-level

Recently, there are more and more image encryption algorithms being proposed based on chaotic systems. The classical architecture employs permutation plus diffusion. However, the traditional permutation operation can only shuffle the positions of the image pixels, but not change the pixels values and not implement the bit shifting in different bit planes. We can also see that most of them are key-dependent structures. So, they cannot resist efficiently the known-plaintext or chosen-plaintext attacks. To overcome these existing low-security problems, we suggest a new feedback image encryption scheme, in which a mathematical model is established for updating the initial conditions of the chaotic system in the permutation stage. Then, the secure SHA-3 algorithm is employed further to generate the keystream combined with new initial keys of the chaotic system in a diffusion stage. Both keystreams generated in the permutation and diffusion processes are dependent on the plain-image. Theoretical analysis and numerical simulations demonstrate the high security of the proposed encryption scheme, especially the ability to resist the known-plaintext and chosen-plaintext attacks.