【作者】 孟博；

【导师】 吕伟杰； 高南珪；

【作者基本信息】 天津大学 ， 控制工程， 2018， 硕士

【摘要】 随着信息技术网络时代的潮流发展,网络信道中多媒体信息的安全性受到各方面的挑战,数字图像作为人们日常生活中常用表达方式,数字图像安全成为焦点关注问题,各种加密手段得到发展进步。混沌理论作为近年来的伟大发现,其高敏感性、伪随机轨道特点为密码学的结合提供了可能性,本文结合现阶段数字图像加密的发展现状,根据现有的先验混沌模型,分析了一维到高维的混沌轨迹特性,针对混沌理论和加密算法做了以下工作:1、首先阐述了密码学与混沌理论各自的理论基础,介绍了混沌的特性以及工程判定准则,并着重分析了常用的几种一维至高维混沌模型,给出了图像加密的指标分析。2、其次提出一种基于复合混沌和DNA序列编码的图像加密算法,针对一维混沌映射控制参数变化范围不连续、混沌序列分布不均匀等缺陷,给出了复合混沌改进方案,作了详细的映射分岔图以及Lyapunov指数分析;并引用了DNA序列编码计算方法,提出了改进的加密方法,设计了基于复合混沌及DNA异或计算的加密反馈机制。通过实验表明提出的算法加密效果良好,扩充了密钥空间,加大攻击破译难度,并客观上从各种指标分析验证了算法具有很好的抗攻击能力。3、最后提出一种基于超混沌系统的ART加密改进算法,文中详细阐述了二维相位掩膜Arnold系统置乱加密的模型,针对ART加密所表现出的加密效果和效率均欠佳以及不适于非方形图像加密的缺陷,本文引入了超混沌Lorenz系统进行改进,结合ART置乱的加密特点以及超混沌序列均匀分布的特征,采用分块加密方式和置乱扩散的加密思想。通过各方面的仿真实验分析表明,改进算法有着很好的统计特性和加密效果。更多还原

【Abstract】 With the development of information technology,the network channel security in the multimedia information is faced with all aspects of challenge.Digital image is a common expression used in people’s daily life,and its encryption becomes the focus problem.All kinds of encryption algorithm make great progress.Chaos theory is a great discovery in recent years,whose high sensitivity and pseudo random orbit characteristics provide the possibility for combination of cryptography.Based on the present development status of digital image encryption and existing prior chaos model,the thesis analyzes the characteristics of one dimension to high dimensional chaotic trajectory and does the following work.At first,the thesis expounds the cryptography and chaos theory to their respective theoretical foundation,and introduces the characteristic of chaos and engineering criterion.It analyzes the commonly used several kinds of one-dimensional to high-dimensional chaos model,and gives the index analysis of image encryption.Secondly,we put forward a novel image encryption algorithm based on compound chaotic system and Deoxyribonucleic Acid(DNA)sequence coding.Due to the fact that one-dimensional chaotic map has defects of discontinue control parameter range and uneven distribution of chaotic sequence,the thesis gives the compound chaotic improvement program,and makes the detailed mapping of the bifurcation diagram and Lyapunov index analysis.Then the calculating method of DNA sequence coding improved encryption method is proposed,which designs encryption feedback mechanism based on compound chaos and DNA exclusive or computing.The experiments show that the proposed algorithm has good encryption effect,expands the key space,and increases the difficulty of deciphering attack.The simulation results verify that the algorithm has good performance against the attack via various index analysis.Finally,we put forward an improved ART encryption algorithm combined with hyper chaos system.The thesis expounds on the two-dimensional phase mask Arnold system scrambling encryption model.Due to the fact that the ART encryption effect and efficiency are poor,which is not suitable for the square image encryption,the thesis introduces the hyper chaotic Lorenz system.It combines with the characteristics of ART scrambling encryption and uniform distribution of hyper-chaos sequence characteristics,and uses the block encryption and spread confusion encryption methods.All aspects of the simulation analysis indicate that the improved algorithm has good statistical properties and encryption effect.更多还原