Security Analysis Of A Class Of Image Chaos Encryption Algorithms

Chaos cryptography is a cross-discipline that combines cryptography and chaos theory.It has attracted the attention of scholars from all over the world as early as the late 1980 s.Especially in the context of the current era of big data,digital images have become the main method of information exchange.Therefore,researchers from all walks of life pay more attention to the practicability and security of image encryption systems in the process of using chaotic cryptography for digital image encryption.Sex.Therefore,it is of great practical significance for scholars from various parties to carry out the cryptanalysis of the image chaotic encryption algorithm.This paper analyzes the security of two image chaotic encryption algorithms and finds the possible security flaws in the algorithms.Then,based on the analysis results,the two encryption algorithms are successfully deciphered by selecting the plaintext attack method,and specific details are proposed for the second encryption algorithm.Improve the steps to increase the complexity of the algorithm to resist multiple attack methods including selected plaintext attacks and selected ciphertext attacks.The focus of this article is as follows:(1)The cryptanalysis of an image chaotic encryption algorithm proposed in 2014 with pixel position and bit double reset.The algorithm is a new type of scrambling-replacement structure.The specific encryption steps have two major steps: firstly,perform global scrambling of the pixel position of the plaintext image to obtain the scrambled image;secondly,perform pixel value replacement based on bit scrambling Encryption operation to get the final encrypted image.In order to test the overall performance of the algorithm,the original algorithm performed experimental simulation and statistical analysis on the proposed encryption algorithm,and found from the simulation results and statistical analysis data that the algorithm not only has the performance of a general encryption method with a "scrambling-replacement" structure In addition,the protection against selected plaintext attacks and selected ciphertext attacks is significantly stronger than the existing "scrambling-substitution" encryption method.In addition,the encryption algorithm also improves the performance index of the algorithm in other aspects,so it is compared with the original Some "scrambling-replacement" encryption algorithms have been greatly improved in terms of security and practicability.However,through simulation,it is found that although the scrambling process of the algorithm is related to the plaintext,the statistical characteristics of the image before and after the scrambling have not fundamentally changed,indicating that the algorithm cannot resist the plaintext selection attack.The attacker can still use the selective plaintext attack to decipher.By constructing multiple special plaintext images and inputting them into the encryption algorithm,they can obtain the equivalent encryption key required by the decryption algorithm step by step,and use the equivalent encryption key to successfully restore the plaintext image.(2)The security analysis of the image encryption algorithm based on cyclic shift and chaos system proposed in 2020.The original algorithm includes two parts of cyclic shift position chaos and XOR diffusion.The main feature is to determine the number of cyclic shift bits according to the statistical characteristics of the plaintext image.The original author obtained the encrypted image through the encryption algorithm,and carried out a security analysis on the algorithm.According to the analysis results,the original algorithm was cryptanalyzed by selecting the plaintext attack method,and it was found that the equivalent key can be cracked regardless of the cyclic shift in the encryption process or the XOR diffusion operation,and then successfully obtained the equivalent of the original algorithm Key and restore the plaintext image,and finally propose specific improvements to the original algorithm.In the security performance test part,the data comparison results of the improved encryption algorithm and the original encryption algorithm are also listed.According to the data comparison results,it is found that the security performance of the improved encryption algorithm is higher than that of the original encryption algorithm,and the key space It is also larger enough to resist all kinds of attacks.From the comparison of the data before and after and the theoretical analysis,it is not difficult to find that the original algorithm cannot resist the selected plaintext attack,but the security of the improved algorithm is greatly improved.