论文标题:混沌在网络信息安全中的应用研究
Research on Applications of Chaos to Network Information Security
论文作者 彭军
论文导师 吴中福；廖晓峰,论文学位 博士,论文专业 计算机软件与理论
论文单位 重庆大学,点击次数 115,论文页数 115页File Size1485k
2003-04-02论文网 http://www.lw23.com/lunwen_79578697/ 混沌;时滞;稳定性;同步;信息安全;保密通信;混沌密码;数字水印
Chaos; Time Delay; Stability; Synchronization; Information Security;Privacy Communication; Chaotic Cipher; Digital Watermark
随着计算机技术、网络技术和通信技术的高速发展和广泛应用，特别是Internet的迅猛发展，网络信息的安全与保护问题日益成为亟待解决的关键问题。将混沌理论应用于保密通信和信息加密已成为国际非线性科学和信息科学两个领域交叉融合的热门前沿课题之一，也是国际上高科技研究的一个新领域。本论文主要内容涉及混沌同步理论研究和混沌序列在信息安全中的应用研究。主要研究内容及创新之处：1．对混沌理论在保密通信和信息加密中的应用研究现状进行了分析与概述，提出了目前存在的一些需要解决的关键问题。2．在介绍了几类主要的混沌同步方法的基础上；利用Lyapunov泛函方法，对一类具有混沌现象的时滞神经元系统的藕合同步问题进行了详细的研究，从理论上给出了同步的解析条件，从而避免了条件Lyapunov指数计算的复杂问题。其仿真实验结果证实了同步理论的正确性。由于时滞动力学混沌系统具有无穷维同步吸引子，因而产生的混沌信号更加复杂且难以破译，可望提高加密系统的保密能。3．讨论了传统线性移位反馈寄存器序列如序列等性能上存在的不足；在此基础上，从理论上分析了Logistic-map和Chebyshev-map混沌序列的特性，并作了大量的对比分析实验，包括混沌序列的随机性、平衡性、游程特性、自相关和互相关函数、奇/偶自相关和互相关函数、相关旁瓣均方值以及线性复杂度等多项指标。并研究了这些指标与初值、系统参数、序列长度等之间的关系。4．研究了如何利用混沌序列进行保密通信的问题，提出了两种可行的保密通信方案。第一种方案实现了载波的自同步，即可以从接收信号直接提取出同步信号，不存在同步误差传播问题，它特别适合于理想信道或信噪比高的信道。第二种方案则利用混沌序列的理想相关性能，实现了扩频保密通信，并给出了误比特率与扩频因子之间关系的近似公式；仿真实验证明两种方案的保密性好，有一定抗噪能力。5．在混沌理论与传统密码学的结合应用方面作了一些有意义的探讨。对传统密码学加密原理理解的基础上，对比分析了混沌系统具备的如扩散、扰乱等密码学特性。针对一类混沌加密系统存在的不足，提出了一种改进的多级混沌加密系统，详细地描述了系统的加解密算法，并对该系统的安全性能进行了深入分析，如扩散扰乱特性、密钥空间、弱密钥问题和抗密码学分析等。由于该系统采用了两级混沌系统，并使用了置换器，使得密码分析更加困难，较原系统进一步提高了安全性。从工程的角度考虑了加密速度的提高问题，并给出了该加密系统软件实现的主要关键技术。6．在介绍了数字水印技术的概念、研究现状、特点和应用情况下，提出了一种新颖的基于模糊C均值聚类（FCM）和DCT变换的混沌数字水印自适应算法。其创新之处在于应用基于人类视觉系统（HVS）的FCM聚类结果，将隶属度作为混沌水印信号的嵌入强度，从而实现了水印的自适应嵌入，这使得水印图像更具透明性。实验结果也验证了该算法具有的较强透明性，同时也表明算法对图象增强、滤波等几类攻击方式具有抵抗力。由于引进了混沌信号，使得水印产品的安全性得到了很大的提高。并且混沌信号数量众多、容易产生和控制，可以大批量地对数字化产品进行版权保护。7．最后论文对研究工作进行了全面的总结，并对今后的研究方向进行了展望。
With the rapid development and extensive applications of computer technology, network technology, communication technology, and Internet in particular, the security of network information is becoming increasingly a key problem that must be solved urgently.That applying chaos theory to secure communication and information encryption has already become one of the hot research projects on the combination of nonlinear science and information science, and it is a novel branch of high-tech research fields. The main contents of this paper include the research on chaos synchronization theory and chaotic sequences application in information security.The main research contents and originality of this paper can be summarized as following:1．The author has summarized the current situation of application research on privacy communication and information encryption by using chaos, and pointed out that several existing problems should be solved at present.2．Several main chaotic synchronization techniques are introduced in this paper, and synchronization of a coupled time-delay chaotic neural system is studied, then the general synchronization condition in analytic is obtained by using Lyapunov functional method, consequently the complexity for calculating of the condition Lyapunov exponents is avoided. The computer stimulation result of private communication has illustrated that the theoretical analysis is correct. As the time-delay dynamics have infinite high-dimensional synchronal attractors, and the chaotic signals cannot be cracked easily due to their complexity, thus it is especially expected that the encryption system employing the time-delay dynamic possesses higher security performance.3．The author has discussed that the correlation performance of traditional linear shift feedback register (LSFR) sequences, such as m-sequence is not very ideal. The performances of Logistic-map and Chebyshev-map chaotic sequences are analyzed theoretically, and a lot of analyses and comparison experimentations have been done, including several properties such as randomicity, balance, run length, correlation function, odd/even correlation function, correlation side lobe normal error and linear complexity. The relationships of these properties versus initial value, system parameter and sequence length are studied in detailed.4．The author studied how to utilize chaotic signals to realize secure communication, and two feasible image secure communication schemes proposed based on chebyshev map chaotic sequences. In the first scheme, the chaotic self-synchronization is realized, i.e. the chaotic carrier can be retrieved directly from received signals. Furthermore, the synchronization error cannot be propagated. Hence, the first scheme is very suitable to an ideal channel or a high-SNR (signal to noise ratio) channel. The second scheme makes best use of excellent correlation features of chaotic sequences to realize a direct-sequence spread-spectrum (DS/SS) communication system. The approximate relationship function of BER (bits error ratio) versus spread-spectrum factor is also obtained. The stimulation results demonstrate that both schemes have higher security performances even under the situation of a noisy channel.5．The author has done some meaningful research in the aspect of the application of integrating chaos theory and traditional cryptography. The cryptography properties, such as confusion and diffusion, that chaotic systems possess are analyzed based on understanding of traditional cryptography principle. In order to cope with some shortages that belong to one type of chaotic encryption system, an improved multistage chaotic encryption system is proposed, the encryption/decryption algorithm is given in detail, and makes in-depth analysis of the security performances of the system, such as properties of confusion and diffusion, key space, weak key and capability against cryptanalysis, etc. Because the encryption system exploits two-stage chaotic system, and uses a permutator, it makes cryptanalysis more
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