【作者】 林俊晓；

【导师】 沈民奋；

【作者基本信息】 汕头大学 ， 信号与信息处理， 2009， 硕士

【摘要】 随着网络技术的发展和信息交换的日益频繁,信息安全问题日益突出。信息技术的发展对信息安全提出了越来越高的要求,迫切需要发展新的理论和先进的技术。而数字图像作为多媒体信息中最重要一种表达形式,具有形象、直观和生动的优点,它已经成为当今乃至今后信息表达方式的主流,在带给人们生活便利的同时,也存在着诸多的安全隐患,因其数据量大、冗余度高,已给传统加密方法提出了挑战,混沌理论在图像信息的加密上应运而生,体现了强大的生命力。本文详细的介绍了密码学的现状,对各种数字图像加密技术进行分析,并对比各类图像加密方法的性能优缺点。研究了两种基本的混沌图像加密方法,并引出复合混沌理论的概念、原理和性质,复合混沌系统在图像加密领域中的应用,再介绍图像置乱技术的原理与应用。最后结合复合混沌技术和图像置乱技术设计了一种新的基于复合混沌的数字图像加密算法。本文方案中采用的复合混沌运算掩盖了混沌子序列的分布特征,改变了原混沌系统的动力学行为,从而使其保密性能得到提高,其保密性要优于普通的低维混沌序列。而且置换加密放在置乱加密之前,增强了置乱加密的抗攻击能力,靠收集图像特征的置乱加密破解方法是不可行的。实验结果表明:本文设计的方案具有初始值敏感性,密文直方图分布均匀,密文相邻像素点之间的相关性性能得到很大提高,在受到剪切攻击之后能够很多好的恢复出明文信息,总体来说,本文方案具有良好的抗统计分析能力和强的抗剪切攻击的特性。更多还原

【Abstract】 With the development of network technology and the increasingly information exchange, information security issues have become increasingly prominent. Because of the rapid development of information technology, increasing information security and new information security theory and advanced technologies are required urgently. With the advantages of intuitive and vivid, digital image which is the most important expression of multi-media information,has been referred to as the current expression as well as the future mainstream of information. While it brings convenience to people’s lives, and in the same time there are many security risks. Traditional encryption methods have been put forward to the challenge because of its large amount of data, and high redundancy. Chaos Theory in the image information of encryption came into being, reflecting the strong vitality.This paper introduces the status of cryptography in detail,analyses a variety of digital image encryption technology,compares to vrious encryption methods and the performance of the advantages and disadvantage.Then,presents two basic chaotic image encryption methods,thus to the composite chaotic concepts, principles and characteristics,and the application in the field of image encryption with composite chaotic system.Also introduces the principle and application of the image scrambling technology.Finally,this paper propose a new digital image encryption algorithm based on composite chaotic by integrate the composite chaotic and image scrambling technology.In this paper, the program uses in the composite chaotic operation cover up the characteristics of the original sequence of chaotic, changes the dynamic behavior of chaotic systems in order to improve the performance of its secrecy, the confidentiality is superior to an ordinary low-dimensional chaotic sequence. And encryption on the replacement before scrambling encryption, has enhanced the anti-attack capability of scrambling encryption. That breaking solves method depending on collecting the image characteristic is no feasible. The experimental results show that: In this paper, the design of the program with the initial value of the sensitivity, the histogram distribution ciphertext, correlation between adjacent pixel performance greatly improved. It could restore the explicit information greatly after the shearing-attack. Overall program in this article has a good capacity of anti-statistical analysis and strong anti-shear characteristics of the attack.更多还原