Research On Image Encryption Algorithm Based On Multi Chaotic System

With the popularity of smart phones and personal computers,as well as the support of advanced communication technology,massive text information,audio,image and other digital information are transmitted on the Internet at any time.As one of the most important information carriers on the network,digital image security is particularly important.Image encryption technology is the most commonly used means to protect image information.Because digital image has many different characteristics from traditional text information,traditional text encryption technology is no longer suitable for image encryption.The pseudorandomness,initial value sensitivity,ergodicity and other chaotic characteristics of chaotic system coincide with the requirements of cryptography.Therefore,chaotic system is introduced into image encryption and has been widely used.For an image encryption algorithm based on multi chaotic system,it can be divided into pseudo-random sequence generator(namely chaotic system)and image encryption algorithm.Image encryption algorithm can be further divided into scrambling process and diffusion process.Therefore,this thesis mainly focuses on image encryption algorithm and new multi chaotic system.The research contents of this thesis are as follows:1.Aiming at the efficiency of scrambling and diffusion in the process of image encryption,a scrambling algorithm which can change the row and column coordinates of pixels at the same time and an adaptive central diffusion algorithm are proposed based on the existing chaotic system.Firstly,the initial values and parameter values of 2D Logisticadjusted-Sine(2D-LASM)and Logistic-Sine System(LSS)are obtained from the SHA256 value of plaintext image.In the scrambling stage,the plaintext image is randomly DNA encoded according to the chaotic sequence generated by 2D-LASM,and a row scrambling matrix and a column scrambling matrix are obtained.The encoded DNA matrix can perform row column scrambling simultaneously according to the two scrambling matrices.In the diffusion phase,a random DNA coding matrix is obtained according to the chaotic sequence generated by LSS,and then the random DNA coding matrix is combined with the scrambled matrix for adaptive central diffusion algorithm.Finally,the ciphertext image is obtained.The simulation results show that the algorithm has excellent security performance and high efficiency.2.Aiming at the shortcomings of 2D logistic sine coupling map(2D-LSCM)and Henon map,two new chaotic systems,new 2D logistic sine coupling map(N2D-LSCM)and new Henon(NHenon)are proposed,which are introduced into encryption algorithm as multi chaotic systems.Firstly,the initial value and parameter value of N2D-LSCM and the initial value of NHenon are obtained from the SHA256 value of plaintext image,and the parameter value of NHenon is the iterative value of N2D-LSCM.In the scrambling stage,the plaintext image is scrambled at the pixel level according to the chaotic sequence generated by N2D-LSCM,and then the scrambled image is encoded with DNA.In the diffusion stage,a random DNA coding matrix is obtained according to the chaotic sequence generated by NHenon,and XOR operation is performed between the random DNA coding matrix and the permutation DNA matrix.Finally,the ciphertext image is obtained.In this thesis,the encryption algorithm is simulated,and the results show that the encryption algorithm not only ensures the security of the algorithm,but also ensures the efficiency of the algorithm.3.Finally,the importance of the research content and the work of this thesis are summarized.In the end,according to the current research situation and the shortcomings of image encryption algorithm based on chaotic system,combined with the development of the times and other factors,it points out the possible research direction or content in the field of image encryption.