基于纠错码的PDF文档数字水印算法

针对PDF文档的结构特点，研究并提出一种新的大容量高鲁棒性的文本数字水印算法。在不改变原PDF文档任何可见属性的前提下。利用PDF文档自身的语法和结构特征嵌入水印信息。算法采用提取文档字符特征码的方法形成的水印，具有较好的唯一性和随机性。同时结合纠错编码和公钥密码算法提高水印的鲁棒性和安全性。实验表明，该数字水印算法具有良好的不可感知性，在确保较大容量的同时仍具有较强的鲁棒性，很好的协调不可感知性、数据容量和鲁棒性三者之间的矛盾。

A New Watermarking Algorithm of PDF Document Based on Correct Coding

Considering the structural feature of PDF document, we present a new high capacity and robust text watermarking algorithm. This algorithm makes use of the syntax and structural feature of PDF document to hide information and does not change any visual attributes of former document. TO insure the exclusiveness and randomicity of watermark, we extract the character eigenvectors of the document to create watermark. Futhermore, oorrect coding and cryptography can advance the robustness and security of watermark. Experiment indicates that this watermarking algorithm realizes perceptual transparency property, high capacity and robusmess at the same time, harmonizing the inconsistency among perceptual transparency property, capacity and robustness.