【作者】 韦军；

【导师】 廖晓峰；

【作者基本信息】 重庆大学 ， 计算机应用技术， 2006， 博士

【摘要】 计算机和互联网技术的飞速发展,将我们的社会带入了信息化时代,使得信息系统的建立己逐渐成为社会各个领域不可或缺的基础设施。任何机构都有需要保密的信息,使得信息的安全成为各界所共同关注的热点。密码系统是解决信息安全问题的最基本的手段。混沌理论和密码学之间有着天然的联系:混沌系统的一些动力学特性大致对应着密码系统的某些安全特征,而具有良好混合性的传统密码系统又暗示着拟混沌现象。从1989年Matthews和Pecora与Carroll分别提出混沌密码学中的两种方案之后,混沌密码的研究进入了繁荣时期,发表了大量的研究结果,尽管相当数量新提出的混沌密码被攻破了,但是仍有很多混沌密码算法直到目前尚未遇到真正有效的攻击。本论文主要研究的是混沌理论在信息安全技术特别是序列密码学方面的应用。具体包括以下工作:1)从多个方面对混沌理论基础作了详细的论述。给出了混沌的定义,描述了混沌运动的特征,并介绍了各种常见的混沌模型和混沌研究所需的判据与准则。2)对当前混沌密码学的发展状况进行了详细的分析、归纳和总结,特别是混沌序列密码的分析和设计方法。。3)成功地分析了印度学者N.K.Pareek等提出的基于多个一维混沌映射的加密算法。首先指出它实际上是一种密钥流独立于明文的序列密码,因而在明文攻击下是脆弱的。随后通过引入两个方程,使用于加密的映射函数由明文决定来克服了密钥流独立于明文这一安全漏洞。4)对Baptista类型的混沌加密算法进行了安全和效率分析。指出了它们性能低下的原因,并通过用一个分布均匀的参数集代替一个固定的参数控制混沌映射来极大地克服了这些缺陷。5)通过总结已经发表的混沌密码学方面的研究成果,提出了一种新的混沌序列密码算法,并且用实验、相关流密码和信息论知识证明它安全和更加高效。6)在分析了已有的流密码设计和相关攻击方法后,总结出一个混沌流密码模型,在信息论和流密码相关理论基础上对它的安全性进行了较彻底的讨论,从而为将来设计新的混沌序列密码算法提供了一种系统的检测安全陷阱的方法,并且说明了要使混沌流密码获得更大的发展,必须将传统的序列密码和信息论知识和混沌理论更加紧密地联系起来。7)最后对论文工作进行了全面的总结,并对今后的研究方向进行了展望。更多还原

【Abstract】 With the rapid development and extensive applications of computer and communication technologies, our society goes into information time. The establishment of information system has gradually become an essential foundation for nearly all fields of our society. As there exists confidential information in any organization, the security problem about this information has become the common focus of both academia and enterprises.Cryptograph provides the most basic method to solve the information security problem. There is natural relationship between chaos and cryptography: strong dynamical properties of chaotic system imply strong cryptographical properties, and the basic approach to design strong cryptosystem implies quasi-chaos. The boom of research on chaotic ciphers occurred from 1989, two chaotic ciphers schemes proposed by Matthews, Pecora and Carroll, and much more contributions are made to get many promising achievements. Although a number of recently proposed chaotic ciphers have been cryptanalyzed, many others have not been effectively attacked yet.This dissertation focuses on the analysis and design of chaotic stream algorithm. The main achievements and originality contained in this dissertation are as follows: Chaos theory is introduced in detail from different aspects and views, the definition of chaos is presented, the characteristics of chaotic dynamics are described, and the criterion and rule of chaos are given.The research status and advances of chaotic ciphers have been summarized, analyzed and overviewed. The analysis and design method of chaotic stream cipher have been expatiated in detail.A chaotic stream cipher by using external 128-bit key and multiple chaotic maps has been discussed. A fundamental defect of this cryptosystem is pointed out and a known plaintext attack is presented. Furthermore, a remedial modification is suggested, which avoids the flaw while keeping all the merits of the original cryptosystem.Based on Baptista’s chaotic cryptosystem, we propose a secure and robust chaotic cryptographic scheme after investigating the problems found in this cryptosystem as well as its variants. A subkey array generated from the key and the plaintext is adopted to enhance the security. Some methods are introduced to increase the efficiency.更多还原