Design Of Image Encryption Algorithm In Space And Frequency Domain Based On Chaos

The rapid development of the mobile Internet and the widespread use of smart terminal devices have gradually networked people’s work and lifestyle,"remote" and "sharing" have become the main components of people’s social lifestyle.With the integration of traditional industries such as computer science and communications,multimedia is gradually entering every corner of human society.Image is a kind of visual multimedia information.It is one of the most important multimedia forms and one of the most important media for transmitting information.Therefore,the security of image transmission has attracted the attention of researchers.Currently,there are two methods to ensure the secure transmission of images: image encryption and information hiding.This paper mainly studies the chaotic image encryption algorithm,aiming to design a chaotic image encryption algorithm with high efficiency and good security.The main research contents and innovations of this paper are as follows:1)In view of the prominent role of chaotic systems in the field of image encryption,this paper has done some research on chaotic systems and their performance analysis.In order to improve the traditional one-dimensional chaotic system with the problem of single structure,small control parameter range,low complexity.Based on Logistic map and sine map,this paper uses nonlinear operations to design a new one-dimensional chaotic map with the advantage of a larger control parameter range,more complex chaotic behavior,and more sensitive to initial values.The bifurcation graph,Lyapunov exponent,trajectory graph and other performance of the chaotic map are analyzed.The experimental results show that the chaotic system has a good chaotic performance.2)This paper designs a chaotic image encryption algorithm based on higher and lower bits image operations.The algorithm divides the image encryption process into two parts.One is row and column scrambling process based on the pixel-level.The paper adopts the improved Joseph traversal to complete this scrambling process.The improved Joseph traversal takes the random sequence as the traversal step to increase the randomness of the traversal process.The other is the encryption process based on higher and lower bits image operations.In this process,there are separate encryption processes and mutual encryption processes for higher and lower bits images.The encryption requirements can be reached without a loop process,which can increase the efficiency of the encryption algorithm.3)This paper designs a chaotic image encryption algorithm based on Haar wavelet in space-frequency domain.This algorithm divides image encryption into two processes: space domain encryption and frequency domain encryption.The first encryption process is frequency domain encryption based on wavelet transform.In the process,the low-frequency coefficients of wavelet transform are scrambled and diffused,and the remaining frequency coefficients are reorganized and scrambled,and then the reverse two-dimensional wavelet transform is performed to obtain the encrypted intermediate image.The second process is space domain encryption,it is used to correct the pixel value of the intermediate encrypted image obtained by frequency domain encryption and ensure distortion-free decryption.This algorithm is a plaintext associated image encryption algorithm,and the plaintext image information is used to generate the key required for encryption.Experimental results and performance analysis show that the algorithm has outstanding characteristic of high efficiency.