扩频水印的安全分级理论及其在算法设计中的应用

Spread-spectrum (SS) has become mainstream in digital watermarking due to its advantages of high confidentiality and high interference-free. However, the security problem with the SS watermarking prevents its application in a wide variety of fields. Recently, the concept of security levels was proposed and has quickly received much attention. This proposal focuses on the theory of security levels of SS watermarking and its application in algorithm design. In terms of the theory of security levels, the equivalency of secret carriers is formulated for the first time. Moreover, we study the constant secret carriers and the probabilistic model that can effectively characterize the statistic of host signals. Based on the above studies, the theory of security levels is normalized. Meanwhile, the orthogonal decomposition theory of host signals is proposed to analyze the security levels of several typical algorithms. In terms of the algorithm design, based on the spherical distribution theory, we define a new class of key-secure SS watermarking methods. Further we use Transportation theory and Recursion technique to optimize the proposed method. According to the above two-fold studies, a complete theory of security of SS watermarking will be built, and the secure and robust SS watermarking algorithm will be developed as well. The proposal is expected to provide a technological guarantee for the copyright protection of digital media contents.

扩频水印因充分利用扩频通信技术的高机密性和高抗干扰能力而获得广泛应用。然而扩频水印的安全性问题日渐成为其全面推广应用的技术瓶颈。近年，国际上为扩频水印提出了安全分级的概念，很快受到关注。本项目研究扩频水印的安全分级理论及其在算法设计中的应用。在安全分级理论方面，首次公式化秘密载波的等价性概念；在研究常量秘密载波和有效表达载体信号的概率模型的基础上完善安全分级理论；并提出载体信号正交分解理论来分析若干典型算法中的安全分级。在算法设计方面，基于球分布理论，定义一类新的密钥安全的扩频水印方法；提出利用Transportation理论来递归优化算法。通过上述研究，进一步发展扩频水印的安全性理论，开发鲁棒的安全扩频水印算法，为媒体内容版权保护提供安全可靠的技术保障。

网络对抗环境下，多媒体数字作品面临着严重的盗版、非法传播等威胁。数字水印成为版权保护唯一有效的技术手段。然而，扩频水印因充分利用扩频通信技术的高机密性和高抗干扰能力成为水印技术中最重要的方法，并获得了最广泛研究。但是，扩频水印的安全性问题成为其全面推广应用的技术瓶颈。本项目研究扩频水印的安全分级理论及其在算法设计中的应用。在安全分级理论方面，首次提出了公式化秘密载波的等价性概念；在研究常量秘密载波和有效表达载体信号的概率模型的基础上完善了安全分级理论；并提出了载体信号正交分解理论来分析若干典型算法中的安全分级。在算法设计方面，基于球分布理论，定义了一类新的密钥安全的扩频水印方法；提出了一种利用Transportation理论来递归优化算法。在该项目的研究基础上，已发表SCI 论文4篇，其中包括2篇顶级的 IEEE Trans. 论文，并申请了国家发明专利2项。该项目研究成果进一步发展了扩频水印的安全性理论，为媒体内容版权保护提供安全可靠的技术保障。