An efficient and secure chaotic cipher algorithm for image content preservation

This paper proposes a new chaotic cipher algorithm for efficient and secure image content preservation, this method is specialized for both standard and medical images, and it consists of two modules which are iteratively performed: chaotic confusion and pixel diffusion. An improved 1D chaotic system (i.e., Logistic Tent System (LTS)) is employed in both confusion and diffusion modules, where its initial conditions are dynamically generated and controlled by the external secret key and SHA-256 hash value of the plain image, conducted to random-like generating key-streams, elevated the sensitivity to small changes on the plain image, and hence ensured the immunity of the proposal against known/chosen plain image attacks. The confusion module is governed by a novel nonlinear bit-shuffling and circular-shifting technique, aiming to achieve bit balancing effect, mixing effect of the pixel value, and certain diffusion mechanism. The diffusion module is ruled by means of an improved XOR operation (eXOR), to further promote the sensitivity to plain image, and accelerate the diffusion mechanism of the overall cipher algorithm. Given that the diffusion mechanism with respect to pixel value mixing are contributed by the two modules, only one encryption round is needed to make a good combination between computational performance, and sufficient security. The obtained results indicate the high performance in terms of execution-time and security level of the proposed cipher algorithm, and validate its robustness against cryptographic attacks, and hence confirm its efficiency for real-time secure image transmission.