Image Encryption Schemes Based On Chaotic System And DNA Computing

With the rapid development of multimedia processing and Internet technology,the dissemination of image-based information is numerous.Therefore,people pay more and more attention to the security of image transmission and storage.To protect image information from unauthorized copying and transmission,and to meet the demands of real-time secure image information transmission,image encryption arises at the historic moment.In this dissertation,two image encryption schemes are designed based on chaotic system and DNA computation,and their performances are tested.The specific research work are as follows:(1)A color image encryption scheme based on new spatiotemporal chaos and DNA computing is proposed.The pixels of R,G,B components of the color image are scrambled with the pseudorandom sequence generated by Chua’s circuit.The DNAencoded R,G,B components are performed by the DNA cyclic shift operation under the control of the key stream generated by a new spatiotemporal chaos.In the first round of diffusion,the DNA cyclic shift is used to overcome the shortcomings of traditional DNA calculations such as bases can not be converted to each other and enhance the diffusion effect.In the second round of diffusion,the DNA decoded R,G,B components are respectively performed XORed with the binary matrix,two rounds of diffusion improve the security of the algorithm,and the R,G,B components are combined to obtain a color encrypted image.In this cryptosystem,Chebyshev maps,as the basic map of the traditional coupled mapping lattice,construct the new spatiotemporal chaos,which not only overcomes the shortcomings of typical spatiotemporal chaos,such as low randomness and many periodic windows,but also has a larger key space as a sequence generator.Experimental results show that the performance indicators of the cryptosystem are very close to the theoretical values,meet the security requirements.(2)A double image encryption scheme based on hyper-chaotic system and DNA sequence is designed.The initial values and control parameters of chaotic systems are updated by the SHA-256 hash value generated by the plaintext image,which effectively resists the chosen plaintext attack.In the process of scrambling,the optimized Arnold matrix transformation is used to scramble the double image sequences,and the elements of the Arnold matrix are generated by the hyper-chaotic Chen system.From scrambling the two-dimensional image to scrambling the one-dimensional vector,this method reduces the scrambling time and has a good scrambling effect.In this scheme,the matrix calculated from the DNA circle distance is used for XOR diffusion,which not only establishes the association between the two images,but also avoids the DNA decoding operation and improves the encryption speed of the algorithm.The experimental results show that the scheme has high encryption speed and plaintext sensitivity.