【作者】 李欣；

【导师】 袁东风；

【作者基本信息】 北京邮电大学 ， 信息安全， 2012， 博士

【摘要】 作为信息安全领域的一个重要分支,信息隐藏理论及其相关技术近年来在数字版权保护、签名认证、篡改检测、保密通信等领域得到了快速的发展。与此同时,这些技术逐步开始依赖于载体和嵌入式的数学方法,这使其发展受到了一定的限制。众所周知,信息隐藏的目的在于“隐藏信息的存在”,并不关注隐藏的手段和方法。因此,从这一目的出发,研究信息隐藏实现机理、隐藏模型及其安全性等基础理论,打破载体和嵌入式算法的限制,对信息隐藏的发展具有重要意义。信息隐藏的实现离不开攻防双方,本文从攻防双方的角度就信息隐藏的实现模型及其安全性问题进行了讨论。主要完成了以下工作：(1)建立了信息隐藏实现空间模型,将信息空间划分为4个部分。论文从攻防双方的角度分析,以“信息不对称是实现信息隐藏的基础”为主要观点,定义了不对称信息空间：感知差值空间和记录差值空间。在此基础上,从攻击者的角度将信息空间划分为：记录可感知空间Ao、感知未记录空间A1、记录不可感知空间A2、未记录不可感知空间A3等4个部分。其中,除A0外,其他3个空间均可以被利用实现信息隐藏。(2)提出了基于行为的信息隐藏安全性分析方法。根据攻防双方的行为特点,从攻击者的角度将信息空间划分为4个部分,分析表明该划分与隐藏空间模型的划分具有一致性。进一步地,利用攻防双方行为的不确定性定义了信息的内容安全和存在安全、信息隐藏行为的内容安全和存在安全等被动安全条件,分析和讨论了不同空间内的安全性。(3)给出了在“感知未记录”空间内实现信息隐藏的算法实例。指出感知未记录空间内实现信息隐藏的可能方式：利用“不记录”的行为或“不记录”的信息内容进行信息隐藏。特别地,给出了在“会议记录”,“招聘启事”等常用文体上利用“不记录”行为实现的信息隐藏实例。此外,还阐述了利用题库中的答案信息和网站中的隐藏链接信息等作为携密信息的算法思想,并总结了该类算法的一般特点。(4)给出了在“记录不可感知”空间内实现信息隐藏的算法实例。根据waV音频文件在经过AMR编解码后分段能量比值的分布特性,设计了三分段能量比音频信息隐藏算法。性能测试显示：在相同分段长度下,新算法的峰值信噪比要大于原有的三分段能量调节算法,同时其针对AMR语音编码的鲁棒性也要优于现有一般算法。(5)给出了在“未记录不可感知”空间内实现信息隐藏的算法实例。尝试利用信息分存和零水印相结合的方式设计了3种图像信息隐藏算法。算法均选择两幅图像作为分存载体,利用多项式算法设计分存方案,分存时只对一幅图像进行修改。其中,前两种算法采用本文提出的模逆特征函数作为主要特征设计零水印,后一种算法以图像的最高两位和最两位低位作为主要特征,通过联合编码设计零水印。性能分析和测试显示：3种算法在性能上具有类似的特点,可应用于隐蔽通信和图像的篡改检测。(6)从攻防双方的角度,对其他信息隐藏问题进行了初步探讨,提出有关信息隐藏的一些设想和疑问。更多还原

【Abstract】 As a branch of the information security, the theory of information hiding and its technology are developed rapidly in digital copyright protection, authentications, tamper detection, secure communication and other fields. However, the technolgy gradually began to rely on the carriers and the embedded method of mathematic. As it is known, the key purpose of information hiding is to "hide the existence of information" without any attentions to the means and methods. Therefore, inorder to break the limitations of the carriers and embedded algorithms, it is necessary to study the basic theories such as the implementation mechanism, the models and security of information hiding. And it will be of much significance for the development of information hiding.The attacker and defender are the essential role in information hiding. The implementation mechanism and the security of it were discussed in this dissertation basing on the angle of the two sides. And the main efforts are as bellow:(1) Established the implementation space model of information hiding, and divided the information space into four parts.A number of information hiding cases showed that the "information asymmetric is the basis for achieving information hiding", and then the asymmetric information in both record and perception space were defined. According to the definitions, the information space was divided into four parts:recorded-perceivable space A0; perceivable-unrecorded space A1; recorded-unperceivable space A2; unrecorded-unperceivable space A3.Here, except space Ao, all the other spaces can be used to hide information.(2) Proposed a method based on the behaviors to analyze the security of information hiding.Firstly, the information space was divided after analyzing the behaviors of the attacker and defenser. And the result shows that the divisions are the same as the implementation space model.Finally, according to the uncertainty of information hiding behavior, the content security and existence security of information, content security and existence security of behaviors were defined to discuss the security issues in the different spaces.(3) Given algorithm instances of information hiding in unrecorded-perceive space.Firstly, possible ways to achieve information hiding in unrecorded-perception space were pointed out:using the content of "unrecorded" information or using the behavior of "unrecording".After that, the algorithm based on the behavior of "unrecording" was designed and the examples were given based on the "meeting records" and "recruitment notices".Besides, the algorithm ideas using the "answers" of the question database as while as using the hidden link of the website were proposed.(4) Given algorithm instances of information hiding in recorded-unperceivable space.According to the characteristics of the wav file after AMR encoding and decoding, a new audio information hiding algorithm based on amplitude modification was proposed. Tests show that the new algorithm is better in capacity, SNR and the robustness in resisting AMR compression at the same length of the group.(5) Given algorithm instances of information hiding in unrecorded-unperceivable space.Three algorithms were designed based on the information sharing and zero-watermark. The basic idea of each algorithm is:choosing two pictures as the sharing carriers and only modifying one of them, and then using the polynomial algorithm to hide the secrets. The former two algorithms used the module inverse function as the main characters to design zero-watermark and the other one encode the highest two bits and last two bits of the pictures to design zero-watermark. Tests show that all the three algorithms have the similar characteristics in performance. Due to the fragility and transparency of zero-watermark, the algorithm can be applied to the image tamper detection and covert communications.(6) Discussed the other problems of information hiding.From the angle of the two sides, some ideas and issues of information hiding were proposed and discussed.更多还原