Chaotic System Based Image Encryption And Its Cryptanalysis

In today's information age,image data are extremely widely used.And how to transmit and use image data more securely has become a research hotspot.Chaotic systems have many characteristics which are very suitable for the design of cryptographic systems.Therefore,more and more chaotic image encryption algorithms have been proposed.Due to the inherent characteristics of image data such as high information redundancy,compared with traditional encryption algorithms,chaotic image encryption algorithms have advantages in terms of efficiency,security and so on.However,some of the latest chaotic image encryption algorithms still have drawbacks in terms of rationality,practicality,and security.In this dissertation,three latest chaotic image encryption algorithms are investigated.The problems existing in these encryption algorithms are pointed out,and the corresponding chosen plaintext attack algorithms are also proposed.In order to improve the practicability and security of chaotic image encryption,an image encryption algorithm based on the memristive chaotic system and discrete logarithm is designed.Finally,in view of the problems still existing in the latest chaotic image encryption algorithms,this dissertation proposes another efficient chaotic image encryption algorithm that can effectively resist attacks.The following are the main research contents and innovative achievements of this dissertation:(1)The image encryption algorithm based on the integrated chaotic systems is studied in this dissertation.And the problems of the algorithm exsiting in the conversions of integer sequences and the permutations of rows/columns etc.are determined and then improved.This dissertation also cryptanalyzes the algorithm and proposes the corresponding attack algorithm.At last,some improvement suggestions are put forward on the uses of chaotic sequences,the ability to resist attacks and so on.(2)The hyperchaotic image encryption algorithm based on Deoxyribo-Nucleic Acid(DNA)encoding and scrambling is investigated in this dissertation.And the problems of the algorithm exsiting in the conversions of chaotic sequences,the calculations of permutation subscripts,and the uses of chaotic sequences are pointed out.Finally,some suggestions for further improvements are presented in this dissertation from the generations of initial values and the uses of chaotic sequences etc.(3)The image encryption algorithm based on two-dimensional combined maps is studied in this dissertation.The problems of the algorithm existing in the generations of system parameters,the design of secret key and so on are pointed out.In this dissertation,the algorithm is also cryptanalyzed,and an attack algorithm for constructing and solving the XOR equation group by the chosen plaintext attack is proposed.At last,some suggestions for further improvements are put forward.(4)An image encryption algorithm based on discrete logarithm and the memristive chaotic system are proposed in this dissertation.The algorithm adopts memristive chaotic sequences,discrete logarithm,and plain image hash values to enhance the permutation and diffusion process,and utilizes the generators to expand the key space and enhance the ability to resist the chosen plaintext attack.At last,this dissertation verifies the practicality and security of the algorithm by theoretical analyses,simulation tests,and comparative analyses.(5)Aiming at the problems existing in the latest chaotic image encryption algorithms,this dissertation designs a plaintext-related chaotic image encryption algorithm based on discrete logarithm and DNA sequence operation.The proposed algorithm introduces discrete logarithm and plain image hash values in each encryption step,which can effectively resist the chosen plaintext attack.In addition,by introducing DNA sequence operation with high parallelism,and changing the usage strategy of the plain image hash values,the encryption efficiency is also significantly improved.Finally,relevant theoretical analyses,simulation tests,and comparative analyses confirm the practicability and security of the algorithm.