Reverse-engineering a watermark detector using an Oracle

Abstract

The Break Our Watermarking System (BOWS) contest gave researchers three months to defeat an unknown watermark, given three marked images and online access to a watermark detector. The authors participated in the first phase of the contest, defeatingthe mark while retaining the highest average quality among attacked images. The techniques developed in this contest led to general methods for reverse-engineering a watermark algorithmvia experimental images fed to its detector. The techniques exploit the tendency of watermarkalgorithms to admit characteristic false positives, which can be used to identify an algorithm or estimatecertain parameters.