Research On Color Image Encryption Algorithm Based On Chaos Theory

Under the background of the era of network communication,digital images have become an important source for people to obtain information.Images in military,medical and other fields are confidential and private,and if they are intercepted by attackers during the transmission,it may cause unpredictable serious consequences.Therefore,ensuring the security of image transmission is an important and urgent task.Considering the adaptability of chaos and cryptography,in view of the security and reliability of digital images in network transmission,two chaotic system with excellent performance are constructed in this paper,and on this basis,two types of image encryption algorithms are proposed.The specific innovations and work are as follows:（1）Aiming at the problems of simple structure and easy prediction of output trajectories in one-dimensional chaotic maps,two two-dimensional chaotic systems,2D-CCSL and 2D-SLSM,are proposed.Perform a cosine operation on the coupled result of one-dimensional Sine map and one-dimensional Logistic map,and extend the phase plane from one-dimensional（1D）to two-dimensional（2D）to obtain 2D-CCLS;Multiply the one-dimensional Logistic map and the one-dimensional Sine map,then scale the result,use the mod operation to limit the result to 0～1,and extend the phase plane from 1D to 2D to obtain2D-SLSM.Compared with three existing chaotic systems,the constructed 2D-CCLS and2D-SLSM have good performance with more complex and unpredictable outputs.（2）An image encryption algorithm based on 2D-CCLS and DNA coding is proposed.Using the constructed two-dimensional chaotic system under the control of the key to generate several different chaotic matrices,after four rounds of scrambling-diffusion operations,the image pixel positions are completely scrambled,and the small difference is diffused to all pixels of the cipher-text,which ensures the validity and reliability of encryption,the image rotation is interspersed in the middle,and the pixel position is confused again.Finally,the DNA encoding and recombination are performed,so that the pixel value is subjected to another diffusion operation.The security analysis of the simulation results of the encryption algorithm is carried out from seven aspects,the key length is 256 with a large enough key space,the NBCR is maintained at 50%in the entire range,reflecting the strong sensitivity of the key,the detection results of NPCR and UACI are also within the range,and the ability to resist differential and noise attacks is strong,so the security and encryption speed of the entire encryption process are guaranteed to a certain extent.（3）A color image encryption algorithm based on 2D-SLSM and Arnold transform is proposed.First,the key is used to generate the initial state value to control the constructed two-dimensional chaotic system to generate a series of chaotic matrices,which assist the subsequent operations to transform the position and value of the image pixels;then perform Arnold transformation on each component of the color image,use a new scrambling-diffusion encryption algorithm processes the horizontally connected images,adding cyclic shift to increase the randomness of the algorithm.Finally,the pixel XOR operation can selectively change the pixel value to ensure the reliability of the system.The security of the algorithm is analyzed from seven aspects.The key space is larger than the standard 2¹⁰⁰,the NBCR is close to the standard 0.5,the NPCR and UACI values are within the specified range,and the correlation of adjacent pixels is close to 0.The experimental results show that the algorithm can resist certain attack methods and has high security performance.