Research And Implementation Of Digital Image Encryption Algorithm Based On Chaos Theory

With the development of Internet,5G mobile communication technology and the widespread application of various mobile terminal devices,digital image has become an important carrier of multimedia communication.Image information is stored and transmitted in the public network,how to protect information security becomes particularly important.Due to the high redundancy of image data and the high correlation of adjacent pixels,the traditional encryption scheme is no longer suitable for image encryption.As a deterministic nonlinear system,chaotic system has many excellent characteristics,which makes it very suitable for image encryption.In this paper,two image encryption algorithms are proposed by combining chaotic system with DNA coding and compressed sensing(1)A color image encryption algorithm based on SHA-256,chaotic system and DNA coding is proposed.SHA-256 is introduced into the algorithm to generate the initial value of the chaotic system,so that the key is associated with the image to achieve one secret at a time.The color image is decomposed into three gray images.two dimensional Logistic-adjusted-Sine map is used to scramble the gray matrix and construct a pseudo-random matrix,and then the matrix is partitioned.Using eight DNA coding rules and four DNA computing methods,the bit level diffusion operation of color image is realized,which improves the security performance of the algorithm and enhances the ability to resist attacks.Finally,Arnold transform is used to fold and stretch the gray image repeatedly.Simulation results and performance analysis show that the algorithm has large key space and high security.(2)An image compression encryption algorithm based on SHA-256,chaotic system and compressed sensing is proposed.The algorithm takes plaintext image as SHA-256 input,and obtains the initial value of Hyper-chaotic Lorenz system through calculation,which is used to generate chaotic sequence closely related to image.The image is sparsely represented by three-level discrete wavelet transform,and the wavelet coefficient matrix is obtained.The chaotic measurement matrix is designed by using chaotic sequence,and the wavelet coefficient matrix is compressed to get the measured value.Then,the ciphertext image is obtained by quantizing the measured values,scrambling the rows and columns and bidirectional diffusion.The decryption steps include: inverse bidirectional diffusion,retrograde column scrambling,inverse quantization,compressed sampling matching pursuit algorithm for image reconstruction and inverse discrete wavelet transform.Simulation results and performance analysis show that the algorithm can reduce the amount of data transmission,improve channel utilization,and has good security.