Secure Embedding of Spread Spectrum Watermarks using Look-up-Tables

In an electronic content distribution system, it is preferable to embed forensic tracking watermarks at the client-side to limit bandwidth usage and server complexity. Embedding in these untrusted clients, however, requires secure embedding methods that do not leak unmarked contents or the watermarking secrets. In this work, we propose a look-up-table (LUT) based cipher, similar to Andersen´s Chameleon cipher, for securely embedding spread-spectrum watermarks, which are noise robust and detectable without the original content. We also develop fast detection mechanisms that make the watermark detection feasible for tracking systems with large number of clients. Our fast detection algorithm improves detection speed six orders of magnitude in a typical system.