Research And Implementation Of Image Encryption Based On Lorenz Chaotic System

Today,our society is in a period of rapid development of information and network,as the continuous improvement of the technology and information technology level,the transmission of information and data becomes more and more convenient,and the transmission speed is also faster and faster.As the carrier of information,the ratio of information transmission with image information is increasing,the image may carry a large amount of personal information and personal privacy,so people pay more attention to the security of image information.Therefore,how to ensure the security of the image in the transmission process has been paid more and more attention.With the development of chaos theory,many researchers combined the chaos theory with the secure communication.As the chaotic system has many characteristics,such as the initial value sensitivity,randomness and long term unpredictable,these characteristics are very consistent with the characteristics of cryptography.Therefore,a lot of related encryption algorithms are proposed based on the chaotic system.In this thesis,chaotic system and image encryption algorithm are combined to study the possibility of image encryption with chaotic system.In this thesis,we firstly studied some typical chaotic systems,such as one-dimensional Logistic chaotic system,two-dimensional Henon chaotic system and three-dimensional Lorenz chaotic system,the chaotic system has proved by the attractor phase diagram,bifurcation diagram and Lyapunov exponent,studied the characteristics of chaotic system,expounded the basic principles of cryptography,and compared the similarities and differences between cryptography and chaos.Secondly,we focus on the study of the continuous three-dimensional Lorenz chaotic system,compared the discretization methods for continuous Lorenz chaotic system,and finally selected the Euler discretization method for this chaotic syetem.Based on one dimension and two dimension chaotic system,listed some typicalquantization methods.We found that they are not suitable for the quantification of three-dimensional Lorenz chaotic system after the analysis,so the quantization method of Lorenz chaotic system is proposed.We compared the properties of the pseudo random sequences generated by the Lorenz chaotic system and the previous one and two dimensional chaotic systems.Through the methods of autocorrelation test,NIST international standard test and BSPD local periodic test,we selected the chaotic pseudo-random sequence with the highest randomness,used this sequence for image encryption and carried out a comprehensive security test for image encryption results,proposed an image encryption algorithm based on K-L transform and Lorenz optimal sequence to change the deficiency of pixel correlation.Finally,we designed an image encryption interface based on embedded QT in the embedded ARM platform,and realized the image encryption algorithm based on Lorenz chaotic system on the embedded ARM platform by transplanting the embedded QT library and embedded OpenCV image processing library.