On Zero-watermarking Algorithms For Digital Document Copyright Protection

With the rapid development of network and multimedia technology, the copyrightprotection of document becomes more and more important. As an effective method ofprotection and tamper proofing for important document, digital document watermarkingtechnology has been a hotspot in academic field. This thesis mainly studies digital documentwatermarking algorithms. It introduces the origin, conception, characteristics, and applicationfields of digital watermarking for document. After the analysis of existing digital documentwatermarking algorithms, a new classification is given. The main contributions of this thesisare two novel digital watermarking algorithms for digital documents.A zero-watermarking algorithm is proposed based on Unicode and SHA512transformation for document text content in this thesis. Simulation results indicate that theproposed algorithm is completely robust against attacks irrelevant to document contents,effectively robust against deleting, substitution and tampering. Based on above algorithm, forprotecting non-text elements in documents, a novel image zero-watermark algorithm isproposed by SIFT and SHA512to image in documents. Experimental results show that theproposed scheme can resist both traditional signal processing attacks and geometric attacks,especially cropping and rescaling. Two proposed algorithm are compatible with each other.