Medical Image Encryption Algorithms Based On Chaotic System

Nowadays,we are living in the era of information explosion,it is very important to transmit information securely in the complicated network environment.As a common carrier of information transmission in daily life,image security transmission has attracted the attention of many scholars.The development of telemedicine needs to transmit a large number of medical images containing private information through open networks.In order to protect the security of these private information,researchers generally use image encryption technology to process medical images.In this study,a secure and robust encryption scheme is designed by combining hyperchaotic Lorenz system with Josephus scrambling.The scrambling factor is added to the hyperchaotic system,and another efficient encryption scheme is designed.The main contents are as follows:(1)A new medical image encryption scheme based on Josephus traversing and hyperchaotic Lorenz system is proposed.Firstly,a hyperchaotic system is used to generate a chaotic sequence for the scrambling and diffusion stages of the algorithm.Secondly,in the process of scrambling,Josephus algorithm is used to scramble the image,and the cat map algorithm is used to scramble the image again.Finally,the generated hyperchaotic sequence is used for the forward and reverse diffusion of the encryption scheme to further hide the effective information of the image.In addition,the plaintext is preprocessed,and then SHA-512 is used to compute with it to generate the key,which improves the scheme’s sensitivity to plaintext and increases the key space to some extent.The simulation results show that the scheme can effectively hide the plaintext image information according to the characteristics of medical images,and can resist common types of attacks.In addition,the scheme performs well in the robust experiment,which shows that the scheme can solve the problem of images susceptible to interference in telemedicine.(2)In order to improve the transmission rate and the capability of anti-differential attack,a medical image encryption scheme based on Zigzag scrambling and new 4D hyperchaotic system is proposed.Firstly,the Zigzag algorithm is used to scramble the image once to hide the obvious contour of the image,and the improved cat mapping system is used to scramble the image to remove the obvious texture features again.Finally,the scrambling factor generated by the plaintext image is applied to the process of generating the initial value of the hyperchaotic system,and then the generated hyperchaotic sequence is used to the subsequent diffusion process of the encryption scheme,the high sensitivity of the chaotic system to the initial value is used to improve the anti-difference attack ability of the whole scheme.The simulation results show that the running time of the scheme is greatly reduced,and its anti-differential attack ability is enhanced.