Research Of Compressed Sensing-based Chaotic Image Encryption Algorithm And Its FPGA Implemention

Compared with the text data,image data is not suitable for the traditional text-based cryptosystem because of its strong correlation,large amount of redundant information and huge amount of data.The pseudo-random sequence generated by chaotic system has a very complex structure,which is difficult to analyze,so it has a broad research value in digital image encryption.Therefore,a new simple four-dimensional hyperchaotic system is constructed,and a new fast,safe and practical hyperchaotic image encryption algorithm is designed in this thesis.The main research works are as follows:1.A new simple four-dimensional hyperchaotic system with only three quadratic terms and five parameters is constructed,and the circuit implementation of the system is designed by FPGA to verify the hardware realizability.Then a pseudo-random sequence construction method is designed based on the hyperchaotic system.The dynamic characteristics of the system are analyzed by phase diagram,bifurcation diagram and Lyapunov exponent spectrum,and the feasibility of the designed circuit is proved by simulation software and board level verification.The analysis results show that:(1)the system can maintain the hyperchaotic dynamic behavior stably under the large fluctuation of multiple parameters;(2)in the system with the same computational complexity,the system has a larger Lyapunov exponent;(3)the pseudo-random sequence generated by pseudo-random sequence construction method has high randomness;(4)the FPGA implementation has stable implementation eddect and can keep the hyperchaotic dynamic behavior for a long time.2.Based on compressed sensing and four-dimensional hyperchaotic system,a fast and secure hyperchaotic image encryption algorithm is designed,and a FPGA implementation scheme of Hyperchaotic image encryption is designed based on the algorithm framework.First of all,considering the selective plaintext attack,a hierarchical key mechanism related to plaintext which is based on the Hash function is designed in order to enhance the sensitivity of ciphertext key and plaintext.Second,the measurement matrix generated by chaotic sequence is used to compress and sample the plaintext image,which reduces the amount of encrypted data.Third,a scrambling algorithm based on the numerical value of pseudo-random sequence and a closed-loop diffusion algorithm combining XOR operation and add modulus operation are designed.Finally,the FPGA implementation scheme of Hyperchaotic image encryption algorithm is designed,which proves the hardware realizability of the algorithm.The encryption algorithm has the advantages of short encryption time,large key space,strong key sensitivity and high security.