数字水印的去同步攻击及其对策

有望解决数字媒体版权纠纷的数字水印技术日渐成熟，新算法不断涌现，面临的攻击也与日俱增。去同步攻击通过几何变形使得相关检测器失效，是一个很难应付的攻击。该攻击主要包括全局仿射变换攻击和局域任意扭曲攻击两种。有很多算法能很好对付前者，但后者几乎使现存的所有算法失效。本文对各种对付去同步攻击的对策分类加以综述，并分析了各自的不足，最后指出如何有效地抵御局域任意扭曲攻击依然是一个悬而未决的课题，尚值得深入研究。

Desynchronization Attacks on Digital Watermarks and Their Countermeasures

As a promising means to ascertain the copyright infringement of digital media, digital watermarking technique is getting more and more mature and new algorithms have been emerging. In the meantime, more and more attacks are confronting with it. This paper discusses desynchronization attack in detail, which disables the correlator through geometrical distortions and is very difficult to tackle. It mainly comprises global affine transformation attack and local random bending attack. Many algorithms can well withstand the former, but the latter almost defeats all existing algorithms. We categorize and summarize the countermeasures in detail, and analyze their deficiencies respectively. Finally we point out that how to effectively cope with desynchronization attack is still an open question and deserves a thorough research.