LAUSR

In this paper, we evaluate the security of an image cipher recently proposed. Three different cryptographic primitives, i.e., permutation, diffusion, and cyclic rotation, were integrated in this cipher so as to obtain a satisfactory security performance within a single encryption round. It is found that the equivalent key stream elements can be derived under chosen-plaintext attack. Both mathematical proof and experimental validation are given in detail. Concerning the presented analysis and some common defects of chaos-based image ciphers, an enhanced image cryptosystem based on the single-round permutation–diffusion structure is further developed. Natural and medical images are introduced for experimental verification and performance comparison. The results demonstrate the security superiority of the improved cryptosystem.