Exploiting self-similarities to defeat digital watermarking systems - A case study on still images

Unauthorized digital copying is a major concern for multimedia content providers. Since copyright owners lose control over content distribution as soon as data is decrypted or unscrambled, digital watermarking has been introduced as a complementary protection technology. In an e?ort to anticipate hostile behaviours of adversaries, the research community is constantly introducing novel attacks to benchmark watermarking systems. In this paper, a generic block replacement attack will be presented. The underlying assumption is that multimedia content is highly repetitive. It should consequently be possible to exploit the self-similarities of the signal to replace each signal block with another perceptually similar one. Alternative methods to compute such a valid replacement block will be surveyed in this paper. Then, experimental results on still images will be presented to demonstrate the e?ciency of the presented attack in comparison with other reference image processing operations. Finally, a discussion will be conducted to exhibit the properties that a watermark should have to resist to this attack.