A new fast chaos-based image cipher with a novel permuatation approach

This paper suggests a new fast chaos-based image cipher with a permutation-diffusion structure. In the permutation stage, the original image is scrambled by swapping each pixel with another one at a location chosen by a pseudorandom permutation generated from the logistic map. The initial condition of the map, i.e. the permutation key, is determined by the CityHash value of the original image. Owing to the avalanche property of a hash function and the initial condition sensitivity property of a chaotic system, pixels in two plain-images will be shuffled in different ways even if there is a tiny difference between them. Such a plaintext-dependent permutation method effectively accelerates the diffusion process and increases the diffusion intensity, and consequently the minimum number of diffusion (overall) rounds required to achieve a satisfactory level of security is reduced. In the diffusion stage, the shuffled image data are masked by a keystream extracted from the orbit of Lü system. Thorough security analysis is carried out, and the results demonstrate the satisfactory security of the proposed scheme.