Image Encryption Algorithm Based On Fractional Wavelet Transform And Chaos

With the rapid development of network technology and multimedia technology,the security of digital image information has become a new topic,which is widely concerned.Part of digital image information,which is related to personal privacy,business secrets and even endangers national security,must be encrypted and transmitted in the process of network transmission.Therefore,image encryption technology is attracting more and more attention.FRWT extends the theory of wavelet multi-resolution analysis to the generalized time-frequency domain,so its parameter setting is more sensitive,and its application field is more extensive,which has gradually become the research focus of the industry.The main content of this dissertation is image encryption algorithm based on FRWT and chaos.Firstly,the theory of FRWT is studied.One dimensional FRFT and two dimensional FRFT are analyzed respectively.It is found that the fractional order of two-dimensional FRFT can greatly improve the security of algorithm in image encryption as a key.Therefore,combined with wavelet transform,the FRWT is introduced,and the discrete algorithm of FRWT is implemented.Secondly,the theory of image encryption is studied.The modern image encryption technologies are introduced,in which the most widely used is chaotic encryption.Several commonly used chaotic systems are analyzed;it is found that Logistic map can disturb the pixel values of images.At the same time,several image encryption security analysis methods are introduced.Thirdly,three kinds of common image encryption algorithms are studied and compared,and their simulation and security analysis on the MATLAB7.1 platform are carried out,and their advantages and disadvantages are analyzed.Finally,the image encryption algorithm based on FRWT and chaos is designed,and the simulation and security analysis are carried out,including histogram,correlation,key and mean square error?MSE?and peak signal to noise ratio?PSNR?,and then the four encryption algorithms are compared and analyzed from the chart and data.The simulation results show that the minimum MSE of the image encryption algorithm based on FRWT and chaos is3.625×10^-25,and the maximum of PSNR is315.9958.And it has good encryption effect and security,and improves the key sensitivity,so that the encrypted image is not easy to be cracked.