| In the Internet age,more and more information is transmitted through the image as a carrier,and illegal access,theft pose a great threat to the security of data.In the medical,financial and military fields,the security of digital image is extremely demanding.The problem of safe transmission has become an important focus of attention,and image encryption is an important technique for ensuring image security.This thesis designs two secure and feasible image encryption algorithms based on DNA computing and chaotic mapping.The main work of this thesis include:(1)An image encryption algorithm based on random DNA coding and spatiotemporal chaos mapping is proposed.In order to generate pseudo-random numbers with more chaotic characteristics,the algorithm uses Tent-Sine system(TSS)combined with weighted coupled map lattice to construct a new spatiotemporal chaotic map.The key of the algorithm is generated using the SHA-256 hash of the image and the required parameters are generated using the Lorenz,Logistic,and TSS chaotic maps.In the process of image DNA encoding and computing,the two-dimensional logistic chaotic maps are used to randomly determine the encoding rules and operation rules of the image.Under the control of the key stream,DNA random decoding is performed on the DNA sequence matrix,and then the final encrypted image is obtained.Experimental results show that the image encryption algorithm has good security and strong ability to resist statistical analysis attacks,differential attacks and chosen plaintext attacks.(2)An image encryption algorithm based on chaos and DNA crossover and mutation operations is proposed.The algorithm uses PWLCM chaotic maps and threedimensional Arnold maps as key generators.First,under the control of the key stream,a diffusion operation is performed on the plaintext image pixel values.Then,the DNA matrix sequence is further scrambled and diffused by simulating DNA crossover and DNA mutation operations during gene recombination.In this encryption algorithm,the key stream establishes connection with the plaintext image,so that the generated key stream is dependent on the plaintext image,so the system can effectively defend against differential attacks,known plaintext attacks,and chosen plaintext attacks.Experiments show that the algorithm can resist all kinds of recognized attacks and has strong security.After experiments and comparative analysis have verified the security of the algorithm proposed in this thesis,the superiority of the algorithm is proved by the comparison results of various evaluation indexes.It has certain reference value for future research in the field of image encryption. |
