Research On Pixel Level And Bit Level Image Encryption Algorithm

Today in the 21 st century,with the continuous development of science and technology and the network field,more and more digital images need to be transmitted and saved through the network,and the transmitted image information is likely to contain the secret information of individuals,enterprises and countries.While enjoying the benefits of technology,we may have experienced or are experiencing its harms.For example,we encounter problems in the process of digital image transmission: image theft,the transmission of confidential information in the process of interception and disclosure,information tampering.Therefore,how to better enjoy the convenience,minimize the harm and prevent information disclosure has become the focus of personal and social concern.The research of information encryption technology provides security guarantee for these multimedia data.In the future development of science and technology,it has become a research hotspot for scholars to develop more secure,convenient and efficient image encryption methods to meet the requirements of The Times.This thesis is about the research of pixel-level and bit-level image encryption algorithm.Based on the unique characteristics of chaos,this paper studies and applies chaos theory and chaotic encryption technology.In the first algorithm,Logistic mapping is combined with the improved hyperchaotic system,and the image is encrypted by double chaotic system,which solves the problem that the digital image encrypted by single chaotic system is easy to be cracked.The image block scrambling and the whole row scrambling are combined to solve the problem that the low scrambling degree leads to the low security of ciphertext.The improved hyperchaos is used to solve the problem that the pseudo-randomness of chaotic sequences is not good enough.In the second algorithm,bit level image crossover control scrambling is combined with pixel level image block ring diffusion,which solves the problem that ciphertext security is not high enough due to the simple algorithm.The key space is enlarged by Henon mapping with perturbation factor and the new multi-wing unified chaotic system.BP neural network is introduced to generate more pseudo-random chaotic sequences,which enhances ciphertext's ability to resist attacks.The above two encryption algorithms have passed the image security test and have better encryption effect than the algorithms in the literature.The structure of the paper is divided into five parts:The first part is the introduction part,which introduces the research background and significance of this paper,the research status of chaos,hyperchaos and neural network application in image encryption at home and abroad,as well as the research ideas and research contents of this paper.The second part is the theory of chaos encryption.Firstly,it introduces the origin and definition of chaos.Secondly,it introduces the main characteristics of chaos,the conditions and criteria of chaos generation and several typical chaotic systems.Finally,the method of image encryption is introduced.The third part studies a kind of image encryption algorithm at pixel level.Based on the theoretical knowledge of chaotic and hyperchaotic systems,the image is firstly scrambled by block and row by whole by Logistic mapping.The key flow generated by the improved hyperchaos is used to diffuse the scrambled image three times to obtain the final ciphertext image.Finally,the feasibility and security of the algorithm are verified by experimental simulation.In the fourth part,an encryption algorithm combining bit-level image with pixel-level image is studied.First,Henon chaotic map is used to scramble the bit-level images.Secondly,the BP neural network is introduced,and the new multi-wing unified chaotic system is used to diffuse the scrambled pixel images in four different directions.Finally,through experiments and comparison with similar algorithms,it is found that the encryption effect of this algorithm is better.The fifth part is the summary and outlook.In this part,the main research content of the paper is summarized,and the deficiencies in the paper are explained.