Research On Image Encryption Based On Dynamic Coupled Map Lattice Model

With the rapid development of information technology,information security has received more and more attention.The image as an important medium for transmitting information,the study of its security and confidentiality has attracted a large number of scholars.In addition,chaotic systems have many characteristics suitable for cryptography,such as sensitivity to initial values,pseudo-randomness,sensitivity to parameters,which ensure that when chaotic systems are used for encryption,the algorithm has sufficient secret key space,excellent anti-brute force and good statistical performance.Therefore,applying chaotic systems to image encryption is undoubtedly a good solution to security and confidentiality of image.In this paper,based on the coupled map lattice model of spatiotemporal chaos system,the following three image encryption algorithms based on coupled map lattice model are proposed.These algorithms make up for the defects of traditional methods in encryption or encryption efficiency from different aspects.(1)The idea of dynamic coupled is proposed,which replaces the static coupling coefficient in the original model with the chaotic dynamic coupling coefficient.And applied it to the coupled logistic lattice(CML)model.By analyzing its Lyapunov exponent,bifurcation diagram and spatiotemporal behavior,it can be found that it has the better chaotic dynamics than CML has.Then combined with the modified model,an image encryption algorithm combining bit stream cross-cycle shift and pixel bit matrix XOR diffusion is proposed.(2)Apply the idea of dynamic coupled to non-adjacent coupled map lattice model.Through the analysis of its chaotic dynamic behavior,it is found that the dynamic coupling can still improve the defects of the non-adjacent coupled map lattice model.And on this basis,a fast image encryption algorithm is proposed.The algorithm obtains the cyclic shift value and the row and column shift control through the 0,1 distribution of the bit stream to determine the permutation process.The ciphertext pixel is dependent on the first two ciphertext pixels to obtain a more sensitive diffusion algorithm for plaintext.The algorithm extracts the secret key from the plaintext by Hash-512,so as to improve the sensitivity of the encryption algorithm to the plaintext.(3)The diffusion operation of the image encryption algorithm is improved from the traditional serialization operation to the parallelization operation,which greatly improves the execution efficiency of the diffusion algorithm on the basis of ensuring the anti-chosen plaintext attack.In addition,combining sorting and cyclic shifting,a permutation algorithm with better security and efficiency than traditional full-sequence permutation,single cyclic shift permutation,Arnold permutation,etc.is proposed.Finally,an encryption frameworksupporting this encryption algorithm is given.