Research On Image Compressive Sensing Reconstruction And Encryption Algorithm Based On Chaotic Sequence

As the digital image can express the information intuitively,it is widely used in various industries as the most important information carrier.However,digital images generally have a large amount of data,and they will face many security problems when they are stored or transmitted.Therefore,in order to improve the security and efficiency of digital image storage or transmission,it is necessary to compress and encrypt image data.According to the special sampling model of compressed sensing(CS)theory,CS compression sampling process can be used as a symmetric encryption scheme,and can achieve compression and encryption at the same time.However,the CS measurement matrix can not resist the chosen plaintext attack if it is used as a key and reused;in addition,the measured value after CS sampling contains the energy information of the original image,and there is a risk of leaking energy information if the measured value is stored or transmitted directly.Chaotic system has good cryptographic characteristics such as sensitivity to initial values and parameters,internal randomness and long-term unpredictability,so this paper introduces chaotic system into CS encryption framework to solve the security problem of CS encryption.In addition,the commonly used classical CS reconstruction algorithm has the problem of poor reconstruction effect or long reconstruction time when dealing with large sparse image signals,which reduces the overall efficiency of CS encryption.Aimed at the security and efficiency of digital image storage or transmission,this paper takes the traditional CS image encryption framework as the core,and combined with hyperchaotic system,carries out in-depth research on the problems existing in the process of CS image encryption,in order to improve the security and overall efficiency of image compression and encryption.The main contents are as follows:(1)An image compression and encryption algorithm based on six-dimensional nondegenerate discrete hyperchaos and plaintext-related scrambling is proposed.Firstly,a six-dimensional non-degenerate discrete hyperchaotic system with six positive Lyapunov exponents is designed,which is introduced into the CS image encryption framework and used to construct the measurement matrix and generate the cryptographic matrix of the subsequent encryption process.Secondly,for the problem that the traditional CS image encryption framework can not resist known and chosen plaintext attacks,the SHA-256 value of the original image is used as the key of the chaotic system to generate the cryptographic matrix,and the plaintext-related scrambling and two-way diffusion algorithms are designed to encrypt the measured values.Finally,simulation experiments are carried out on the proposed compression encryption algorithm to analyze and verify the high security and reconstruction performance of the proposed algorithm under low compression ratio.(2)A compression encryption algorithm based on AS-DSVSBMP is proposed.First of all,an adaptive threshold sparse algorithm of image is designed to improve the sparse degree of the original image.Secondly,in order to solve the problems of greedy reconstruction algorithm commonly used in compressed sensing,such as too long reconstruction time and poor adaptive ability in the case of unknown sparsity,a double selection variable step-size backtracking matching pursuit is designed,which significantly reduces the reconstruction time of the algorithm and improves the adaptive ability of the algorithm when the sparsity is unknown.Then,in order to improve the security of the AS-DSVSBMP compression encryption algorithm,the measured values are scrambled and diffusion.Finally,simulation experiments are carried out on the proposed compression encryption algorithm to analyze and verify the adaptive ability,reconstruction efficiency and reconstruction performance of the proposed algorithm when the sparsity is unknown.