【作者】 邓雁城；

【导师】 牛少彰；

【作者基本信息】 北京邮电大学 ， 应用数学， 2006， 硕士

【摘要】 数字水印是一种比较新颖的信息安全技术。它将创作者的创作信息和个人标志通过嵌入系统以人所不可感知的形式嵌入多媒体宿主之中。这个功能使数字水印在安全保护和版权处理等领域有着多方面的用途，比如广播监控、所有者鉴别、所有权验证、操作跟踪、内容认证、拷贝控制和设备控制等。 数字水印研究一直都被“加强水印鲁棒性”的目的所推动，许多关于水印的文章都是在处理鲁棒性这个标准，因而，在鲁棒性方面已经获得了大量有价值的结果。 但是数字水印的另外一个重要特性——安全性却很少受到关注。这首先是因为安全性和鲁棒性这两个概念有点相近，对水印理论一般的、初步的了解很难发觉它们的不同。事实上，隐藏在攻击后面的目的是不足以区分安全性和鲁棒性的。比如，数字图像的压缩对于鲁棒性来说显然是一种攻击，但是，它可能不是故意的，也有可能是故意的(比如，攻击者蓄谋要移除水印)，而后一种情况并不适合归为鲁棒性应对付的范畴。一般来说，鲁棒水印相当于在媒体内容中以不可感知的方式增加了一条很难去除的通信信道，这个信道的容量越大，宿主媒体的降质会越明显。另外，在常规的传输过程中，也有可能产生降质(压缩，低通滤波器、噪声、几何攻击等)。总之，对于鲁棒性，攻击者无非有三个策略：去掉足够多的水印信号能量；介入水印信道；将水印和原始作品分离。 安全性却与此不同。安全性要对付的攻击绝不止是移除水印之类，事实上它已经排除了上面属于鲁棒性范畴的攻击，因为谈安全性先要假设水印体制具有鲁棒性。 在本论文的第三章和第四章中，作者基于通常水印要用于版权和版本保护的事实，说明了数字水印体系对安全性的具体需求，因为有相当大比例的数字水印都会把这种功能需要作为它语义学上的主题。在这两章中，作者对水印安全性的预实施方案进行了细致的分析(分为无密钥和有密钥两种情况)，其目的就是探讨安全性这一概念在水印中的准确内涵。文中严谨地说明密码学和数字水印的关联以及密码技术在水印安全中的重要性。更多还原

【Abstract】 Digital watermarking consists of hiding subliminal information into digital media content, also called host data. It can be the basis of many applications, including security and media asset management.Digital watermarking studies have always been driven by the improvement of robustness. Most of articles of this field deal with this criterion, presenting increasingly more impressive experimental assessments.On the contrary, security has received little attention in the watermarking community. The first difficulty is that security and robustness are neighboring concepts, which are hardly perceived as different. The intentionality behind the attack is not enough to make a clear cut between these two concepts. An image compression is clearly an attack related to robustness, but it might happen intentionally, i.e., with the purpose of removing the watermark, or not. Robust watermarking is defined as a communication channel multiplexed into original content whose "capacity degrades as a smooth function of the degradation of the marked content" in a nonperceptible way. We add that the degradation is due to a classical content processing (compression, lowpass filtering, noise addition, geometric attack ...). The attacker has three known strategies to defeat watermark robustness: to remove enough watermark signal energy, to jam the hidden communication channel, or to desynchronize the watermarked content.On the other hand, security deals with intentional attacks whose aims are not only the removal of the watermark signal, excluding those already encompassed in the robustness category since the watermarking technique is assumed to be robust.In the chapter 3 and chapter 4 of this paper, we address the usually更多还原