Secure detection of public watermarks with fractal decision boundaries

In this paper we will address the problem of constructing a nonparameteric decision boundary for watermark detection. Most current watermarking algorithms have a parametric decision boundary that can be estimated if the pirate has unlimited access to the detector. In this work we propose a fractal decision boundary which can not be estimated. That boundary is obtained by processing the decision boundary corresponding to the underlying watermarking algorithm. The performance of the new technique is essentially similar to any watermarking algorithm from which it is derived.