On the need for signal-coherent watermarks

Digital watermarking has been introduced in the 90?s as a complementary technology for copyright protection. In an effort to anticipate hostile behavior of adversaries, the research community is constantly introducing new attacks to benchmark watermarking systems. In this paper, we present a generic attack strategy based on block replacement. As multimedia content is often highly repetitive, the attack exploits signal?s self-similarities to replace each signal block with another, perceptually similar one. Guided by the principles of the proposed attack framework, we implemented three attack algorithms for different types of multimedia content: video shots, audio tracks and still images. Finally, considering the effectiveness of the proposed algorithms, we identify the properties that a watermark should have to counter this attacking strategy.