Desynchronization Attacks on Digital Watermarks and Their Countermeasures
数字水印的去同步攻击及其对策

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.