Research On The Construction Of Chaotic Sequence And Its Image Encryption

At present,the design of image encryption algorithm based on chaotic system is mainly from two aspects:key system and encryption algorithm.Among them,the choice of key system usually comes from conventional chaotic system,improved chaotic system and constructed hyperchaotic system,and the confusion and diffusion algorithms in encryption algorithms are mostly similar.With the development of research,these algorithms also gradually exposed the existing security problems.In this paper,after studying the characteristics of chaotic sequences and the structure of encryption algorithm,several new key sequence construction methods are proposed to solve some security problems existing in the current algorithm,which are combined with the improved image encryption algorithm and applied to image encryption.The main research work of this paper includes the following three aspects:(1)An image encryption algorithm based on chaotic sequences with quantum keys is proposedThe algorithm first improves the one-dimensional Logistic chaotic system to improve the performance of the key sequence,and enables the chaotic system to generate system parameters and initial values along with the plaintext image.Then a nonlinear algorithm is used to mix the quantum key sequences into chaotic sequences to generate the mixed key sequences.The algorithm randomly selects the input values and parameters of the neural network from a.set of mixed key sequences,generates the image pixel replacement matrix,and achieves pixel confusion through coordinate index.Two different key sequences are used to make the plaintext pixel into ciphertext after two rounds of diffusion.(2)An image encryption algorithm based on dynamic self-feedback chaotic system is proposedThis algorithm constructs a dynamic self-feedback chaotic system,which is a cascade of one-dimensional Logistic chaos,chebyshev chaos and custom m(x)operations.The algorithm homogenizes the key sequences of the dynamic self-feedback chaotic system,and proves the homogeneity through sequence distribution diagram,expectation and variance.The key of the algorithm is generated by the characteristic association of the plaintext image itself.In the process of encryption,the neural network is still used to obfuscate the image,but on the basis of the initial confusion,the bit confusion operation is added,and finally two rounds of pixel-level diffusion operation are adopted to enhance the ability to resist the selective plaintext attack.(3)An image encryption algorithm based on Henon chaotic system with nonlinear terms is proposedThe algorithm uses the two-dimensional Henon chaotic system as the secret key generation source to avoid the problems that the one-dimensional chaotic system is easy to be cracked and the high-dimensional chaotic system has high complexity and low efficiency.In order to improve the security of the key system,the linear term y(n)in the system is replaced by the nonlinear term ey(n)to form a new chaotic system.The algorithm first selects X sequence with better performance as the secret key source,and then construct a pixel replacement table by a set of chaotic sequences to complete the global confusion of pixels.Then,by making full use of the destructive power of non-linear operation to pixel correlation,the scrambling matrix is expanded by 8 times,and the bit-level replacement table of all pixels is constructed by another set of chaotic sequences to complete the bit-recombination step.Finally,another set of chaotic sequences and the secret key parameters Co and m are introduced to complete the diffusion operation of single pixel value.At last,the thesis summarizes the research work and points out the next research direction.Figure[44]Table[23]Reference[83].