Resilient information hiding for abstract semi-structures

Most work on watermarking has resulted in techniques for different types of data: image, audio, video, text/language, software, etc. In this paper we discuss the watermarking of abstract structured aggregates of multiple types of content, such as multi-type/media documents. These semi-structures can be usually represented as graphs and are characterized by value lying both in the structure and in the individual nodes. Example instances include XML documents, complex web content, workflow and planning descriptions, etc. We propose a scheme for watermarking abstract semi-structures and discuss its resilience with respect to attacks. While content specific watermarking deals with the issue of protecting the value in the structure's nodes, protecting the value pertaining to the structure itself is a new, distinct challenge. Nodes in semi-structures are value-carrying, thus a watermarking algorithm could make use of their encoding capacity by using traditional watermarking. For example if a node contains an image then image watermarking algorithms can be deployed for that node to encode parts of the global watermark. But, given the intrinsic value attached to it, the graph that "glues" these nodes together is in itself a central element of the water-marking process we propose. We show how our approach makes use of these two value facets, structural and node-content.