A chaotic image encryption scheme owning temp-value feedback

• A simple but secure chaotic cipher by improving the familiar permutation–diffusion structure is proposed.
• Embedding a plaintext feedback technique into the permutation process to make the new scheme execute in a “one time pad” manner.
• The plaintext/ciphertext feedback technique is employed to generate equivalent key dynamically in the diffusion part.
• Experimental results show that the new scheme owns large key space and can resist the differential attack.

Many round-based chaotic image encryption algorithms employ the permutation–diffusion structure. This structure has been found insecure when the iteration round is equal to one and the secret permutation of some existing schemes can be recovered even a higher round is adopted. In this paper, we present a single round permutation–diffusion chaotic cipher for gray image, in which some temp-value feedback mechanisms are introduced to resist the known attacks. Specifically, we firstly embed the plaintext feedback technique in the permutation process to develop different permutation sequences for different plain-images and then employ plaintext/ciphertext feedback for diffusion to generate equivalent secret key dynamically. Experimental results show that the new scheme owns large key space and can resist the differential attack. It is also efficient.