AHierarchical ExtractionPolicy for content extraction signatures Selectively handling verifiable digital content

Content extraction signatures (CES) enable the selective disclosure of verifiable content from signed documents. We have previously demonstrated a CES Extraction Policy for fragment grouping to allow the document signer to designate which subsets of the original document are valid subdocuments. Extending this ability, we introduce a newHierarchical Grouping Extraction Policy that is more powerful, and for which the encoding is dramatically smaller, than the existing Grouping Extraction Policy. This new Extraction Policy maps naturally onto the hierarchically structured documents commonly found in digital libraries. After giving a motivating example involving digital libraries we then conjecture as to how to enrich their functionality through the use of CESs. We also show how to implement the new extraction policy using XML signatures with a custom transform along with an improved design for the XML signature structure in order to achieve CES functionality.