Randomizing the replacement attack

Billions of dollars allegedly lost to piracy of multimedia have recently triggered the industry to rethink the way music and movies are distributed. As encryption is vulnerable to re-recording, currently all copyright protection mechanisms tend to rely on watermarking. In order to analyze the security of such systems, a new breed of replacement attacks has recently been proposed that strongly affects most modern watermarking systems. A typical replacement attack relies upon the observation that multimedia content is often highly repetitive. Thus, the attack procedure replaces each signal block with another, perceptually similar block computed as a combination of other similar blocks found either within the same media clip or within a library of media clips. We demonstrate that by randomizing the attack algorithm, its performance can be improved in almost all aspects - attack efficacy, distortion, speed, and size of the look-up media library. We describe the logistics of the new attack and an exemplary implementation against a spread-spectrum data hiding technology for audio signals.