A New Medical Image Encryption Algorithm Using Multiple 1-D Chaotic Maps

This paper presents a new chaos-based medical image encryption algorithm using iterative permutation and substitution operation. To address the drawbacks encountered when using the invertible area-preserving chaotic maps, we introduce a pixel swapping-based image scrambling method with permutation keystream sequence generated from the logistic map. In the substitution stage, each keystream element is generated from a 1-D chaotic map selected from a group of three 1-D chaotic maps according to the value of the pixel previous to the one it applies to, making the keystream sequence dependent on plain-image. As a result, the robustness of the proposed algorithm against chosen-plaintext attack is ensured and the diffusion intensity is increased. The results of NPCR and UACI tests indicate that the proposed algorithm takes only two cipher rounds to achieve a desired diffusion effect. Moreover, each of the three 1-D chaotic maps is constructed by combining of two existing 1-D chaotic maps (seed maps). Compared with its corresponding seed maps, the compound map has larger chaotic ranges and more complex chaotic properties while remaining simplicity, making it a good candidate for constructing image ciphers with a sufficiently large key space and high computational efficiency. Our theoretical analysis and experimental results indicate that the proposed algorithm has a high level of security.