Research On Chaotic Image Encryption System Based On Cellular Automata

The fast-paced evolution of Internet,communication,and multimedia technology has resulted in a massive daily transmission of data over networks and storage of that data in either cloud or local environments.Because of the colorful,intuitive and informative characteristics of digital image,it occupies an important position in information transmission.Digital image information security has become a hot issue that people care about,and has also become the focus of research and attention of experts at home and abroad.Compared with text information,digital image information has the characteristics of large amount of data,high correlation between data information,and large data redundancy,which can’t be well applied to the traditional text encryption algorithm.In recent years,with the in-depth research of encryption theory and chaos theory,it is found that chaotic system has its own pseudo-randomness and initial value sensitivity,which is very suitable for the needs of image encryption.It has shown a very good application prospect in the field of image encryption,and image encryption technology has also achieved significant research results.However,there are still shortcomings in using chaotic system only for image encryption with the deepening of research.Scholars continue to try to fuse other algorithms with chaotic image encryption to improve the security and efficiency of encryption system.Cellular automata can be combined with chaotic system to effectively improve the security and efficiency of encryption because of its simple structure,local complexity and parallel operation.Therefore,the image encryption algorithm combining chaotic system and cellular automata is of great research value.By focusing on the characteristics of cellular automata,evolution rules and unified encryption algorithm,two chaotic image encryption systems fused with cellular automata are proposed.The main research work is as follows:(1)A fast chaotic image encryption system based on cellular automata was proposed.In the encryption system,each row of the image is regarded as a cellular space,and the appropriate elementary cellular automata rules are selected according to the pseudo-random sequence generated by the chaotic system to determine the evolution step of the cellular automata.Then,the cellular automata is used to cascade each row and column of the image,and the information of each bit in the image is diffuse to obtain the ciphertext image.The system abandons the "scrambling and diffusion" structure of the classical chaotic image encryption system,which greatly reduces the length of the pseudo-random sequence required by the system and improves the encryption efficiency while ensuring the security of the system.The simulation experiment and the performance comparison analysis of the encryption system show that the encryption system has high encryption and decryption speed and excellent security performance.(2)A chaotic unified image encryption system based on cellular wavelet transform is proposed.The encryption system uses chaotic sequence to generate the required two-dimensional cellular automata rules,and divides the image into eight-bit matrices.Each bit matrix diffuses the image information at bit level through the cellular wavelet transform proposed by two-dimensional cellular automata combined with lifting wavelet transform and two-dimensional reversible cellular automata.The encryption system is a unified encryption system with the same process of encryption and decryption,and solves the problem that the number of rows and columns of the encrypted image is even in the classical unified image encryption system and the image encryption system based on wavelet transform algorithm.The system can encrypt and decrypt images of any size with a single module,which effectively saves hardware and software resources.The results of simulation experiment,encryption system performance analysis and comparative analysis show that the encryption system has good encryption efficiency and excellent encryption performance.