Abstract

In this article, we propose a novel approach to digital watermarking for Vietnamese documents. The target documents need to be converted to PostScript format files before embedding information. Security information is embedded into the documents by shifting up or down a small gap of Vietnamese signs, which are special to Vietnamese documents. This embedded information can be used for copyright protection or tampering detection. The watermarked document will be converted to PDF format, containing only images instead of texts, before being published. During the detection phase, our approach does not need original documents in order to recover the watermarks. Theoretical analysis and empirical experiments show the efficiency and effectiveness of our proposed solution.