Homogenization Of Chaotic Sequences And Its Application In Image Encryption

Since the introduction of chaos theory into cryptography,chaotic cryptography has received the attention of many researchers.The application of chaotic-based cryptography has multiple aspects such as chaotic stream cipher,chaotic hash function,chaotic s-box and chaotic image encryption,etc.While the application of chaotic cryptography encounters the basic of a large enough key space,many other indicators that determine the security performance of the application still need to be considered.The high chaotic security performance is of vital importance.A uniformly distributed chaotic sequence can effectively hide the potential characteristics of the chaotic system,making it more difficult for attackers to find the rule to crack the chaotic system from the probability distribution characteristics of the chaotic sequence.On the reason that the chaotic system is difficult to produce a chaotic sequence with uniform distribution probability density,how to construct a chaotic sequence into a uniform random sequence effectively has become a major breakthrough.The universal algorithm for the homogenization of chaotic sequences proved by the existing theory.After the uniformly distributed chaotic transformation sequence can be produced,it is applied to two application scenarios,chaotic stream cipher,namely the construction of the pseudo-random number generator algorithm and the image encryption algorithm.1.This thesis introduces the specific details of bit transformation of the universal algorithm for homogenization of chaotic sequences.And explains the algorithm improvement based on the theory of bit transformation,the standard first type transient transformation.The standard second type transient transformation is proposed to keep the phase space equally.2.This thesis proposes a kind of integerized piecewise chaotic systems,using the standard second type transient transformation in the integer domain to obtain uniformly distributed integer chaotic sequences.It is used to design image encryption algorithm based on homogenized integer chaotic sequence.3.A chaotic image encryption algorithm is raised based on the chaotic sequence.Adopting the matrix elementary transformation method in the permutation stage of image encryption,and the state value of the model is adjusted by plaintext feedback in the diffusion stage.