Dynamic Multi-image Encryption Based On Parallel Compression And Fifth-order Hyperchaotic System

It is more and more convenient to share,publish,distribute and transmit images via public networks.Image encryption provides protection to the confidential contents.Traditional image encryption schemes require multiple processing and transmission if they are employed for multiple images encryption,and it is un-efficient.Therefore,the simultaneous encryption of multiple plaintext images and the completion of information exchange in a single transmission can improve the efficiency of encryption and transmission.It has theoretical value and practical significance.This paper analyzes the security risks of image transmission and considers the low efficiency of encryption and decryption caused by the huge amount of data.,two new multiimage encryption schemes are proposed combining chaotic system,discrete wavelet transform and compressed sensing technology.The details are as follows:(1)A multi-image encryption algorithm based on discrete wavelet transform and chaotic system is proposed.The low frequency sub-images of multiple images are extracted by discrete wavelet transform.The high frequency regions without important information are discarded.This operation reduces the amount of data to be encrypted and speeds up the operation efficiency of the algorithm.The combination of two low-dimensional chaotic systems is used to generate a new two-dimensional chaotic mapping,which produces a more random and ergodic pseudo-random sequence.The initial value of the chaotic system is composed of plaintext related information and user input,so that the whole encryption system is related to the plaintext,realizing "one map and one cipher".Two encryption processes constitute the key part of the whole encryption scheme to make sure the safety of the algorithm.The security and effectivity of the algorithm are analyzed by way of simulation experiments,and the effectiveness of the algorithm is verified.(2)A dynamic multi-image encryption algorithm based on parallel compression and fifthorder hyperchaotic system is proposed,which can improve decrypted image quality,increase encryption rate and save storage space.The compression sensing technology and piecewise weak orthogonal matching tracking algorithm were used to compress and reconstruct the data of multiple images,which can improve the encryption rate.A dynamic double-layer step scrambling is designed to evenly scramble the sparse coefficient matrix before measuring the image,forming a "sparse-scramber-measure" compression structure,which effectively improves the reconstruction performance of the encryption scheme.The hashing algorithm and random number are used to generate the initial value of the fifth-order hyperchaotic system,and the resulting pseudo-random sequence is used for encryption operation to realize "one graph,one cipher".The new encryption method is simulated to verify its security.