Image Encryption Algorithm Based On Compound Chaos And Transform Domain

With the rapid development of Internet technology and network communication,image has become one of the important carriers of people's information exchange because of its vividness,strong intuitiveness and rich information.While promoting people's communication,it also brings security issues to session information.Since the traditional DES and AES algorithms are mainly for text encryption,and the image encryption efficiency is low and the real-time performance is poor,it is particularly important to explore a secure and efficient image encryption algorithm.As a kind of nonlinear dynamic system,chaotic system has many similar characteristics with cryptography.It is extremely sensitive to initial value and chaotic parameters,and the generated sequence is difficult to analyze.It has the characteristics of good pseudo-randomness and high complexity.These characteristics make it has broad application prospects in image encryption.In this paper,a series of analysis and research on chaos-based image encryption algorithms are carried out.The main contents are as follows:(1)This paper introduces the research background and significance of this topic,and summarizes the current domestic and international research status of some scholars in the field of image encryption.Then the theory of chaos theory and cryptography and the relationship between them are expounded.Then the related technology of chaotic image encryption is introduced.A lot of numerical simulation experiments on chaotic system characteristics are carried out to verify the feasibility of chaos.(2)Aiming at the problems that some encryption algorithms based on Arnold mapping are vulnerable to the selection of plaintext and periodic recovery to the initial state.Henon maps key space is small and there are blank windows.an image encryption algorithm based on compound chaos is proposed.The algorithm uses generalized Arnold mapping to multiply and scramble pixel points multiple times,and the control parameters of aliasing and scrambling are different,which greatly increases the key space and avoids the periodic recovery problem.The number of scrambling is close to the pixel value.Correlated,solved the problem of not being able to resist the choice of plaintext attack.By using the high-dimensional generalized Henon map to generate more complex sequences,the safety hazard of the two-dimensional Henon map due to the existence of a blank window causing the pseudo-randomness of the sequence is effectively reduced.Finally,the diffusion transform combining mode and XOR is introduced,which not only replaces the single pixel value,but also indirectly affects the encryption effect of the pixel gray value of the subsequent point.It is difficult for the cryptanalyst to obtain th e chaotic sequence effectively.Experimental simulation results show that the algorithm has high security performance.(3)Aiming at the problem that the one-dimensional Logistic map has periodic blank window,the distribution of chaotic sequences is not uniform and the histogram of some fractional transform algorithms is not smooth enough,a chaotic image encryption algorithm based on transform domain is proposed.By selecting a non-periodic quantum logistic map,because there is interference correction at the end,the sequence will not disappear every iteration,so the generated chaotic sequence is more uniform and pseudo-random,and the fractional Fourier The combination of transformation and chaotic mapping realizes that the image data is fully changed in the transform domain,and the problem that the histogram is not smooth enough is solved.The two orders of the fractional Fourier transform can add more degrees of freedom to the encryption scheme and increase the key space.Usually the key information of the image is stored in the low frequency part.Encrypting the image using the transform domain method is also beneficial to better protect the low frequency information of the image.Experimental simulation results show that the algorithm has high security performance.