Collusion-resilient fingerprinting by random pre-warping

Fingerprinting of audio-visual content using digital watermarks is an effective means of determining originators of unauthorized/pirated copies. Watermarks embedded in content can trace the traitor responsible for piracy. Multiple users may, however, collude and collectively escape identification by creating an average of their individually watermarked copies that appears unwatermarked. We propose a novel collusion-resilience mechanism, wherein the host signal is warped randomly prior to watermarking. As each copy undergoes a distinctive warp, collusion through averaging either yields low-quality results or requires substantial computational resources to undo random warps. The method is independent of the watermarking scheme used and imposes no restrictions on the watermark signal. We demonstrate the effectiveness of this approach on digital images.