Abstract
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 watermarking process we propose.
We show how our approach makes use of these two value facets, structural and
node-content.
