On Digital Image Encryption Based On SBT Memristor-Induced Chaotic System

With the advent of big data and the internet of things era,massive amounts of information interact on the internet every day,and information security has become a hot issue.The images in many information carriers have the characteristics of being vivid and having large amount of information,which often become the object of being stolen and attacked in the network.Therefore,it is especially important to encrypt the image information to protect the rights and interests of the information owner.The image information has the characteristics of having large amount of data and uneven energy distribution,which makes the traditional encryption method less suitable for digital image encryption.While the memristor based chaotic system,having high sensitivity to the initial value,pseudo-randomness and ergodicity,is capable of generating enough random numerical sequences and a large enough key space.Therefore,it is ideal for encrypting digital images.The SBT memristor manufactured in the laboratory is a kind of nonlinear component with memory function.In this thesis,the chaotic sequences with good randomness,generated by a SBT-based memristor chaotic circuit,is combined with multiple encryption methods to carry out digital images encryption and decryption experiments.By analyzing and comparing the experimental results,a digital image encryption and decryption scheme based on SBT memristor chaotic system is further designed.Finally,the performance index of the encryption system is calculated and analyzed to verify the efficiency and security of the encryption system.The main research contents of this paper are as follows:(1)The concept and properties of memristor are explained and the mathematical model of SBT memristor is introduced;the definition and characteristics of chaos are described and the dynamic analysis method used in this paper is introduced;and the basic concepts,methods and performance indicators of digital image encryption are briefly analyzed through the examples of encryption.(2)The fifth-order SBT memristor chaotic circuit is designed and its mathematical model is established.Based on this mathematical model,the dynamics analysis of the system is carried out using Lyapunov exponent,phase trajectory,bifurcation diagram and Poincare section.(3)The chaotic sequence generated by the SBT chaotic system is randomly checked,and the chaotic sequences through the test are processed to obtain the ciphers used for image encryption.Then different encryption methods such as random scrambling,non-repetitive scrambling,one-dimensional vector scrambling,exclusive or diffusion and cumulative modular diffusion are combined to encrypt and decrypt the digital image and to analyze and evaluate the experimental results.(4)On the basis of the previous experiments,a digital image encryption scheme is designed by combining scrambling,diffusion and rotation,and the decryption method is given.After testing,the scheme can effectively encrypt and correctly decrypt the digital image.Finally,several performance indicators of cryptosystem are analyzed,including encryption and decryption speed,ciphertext statistical characteristics,information entropy,key sensitivity,key space and sensitivity of plaintext.The results show that the performance of each index is good,so the design of image cryptosystem based on SBT memristor-induced chaotic circuit in this thesis has the practical value.