基于PDF文档结构的数字水印算法

在数字产品日益普及的今天,PDF文档的版权保护问题已成为信息安全领域研究的热点。通过分析PDF文档的结构及相关数字水印算法,针对当前一些大容量文本水印算法存在增加文档大小的缺陷,提出了一种基于PDF文档结构的数字水印算法。该算法利用行末标识符不会在文档中显示的特性,通过等量替换PDF文档中具有固定格式的交叉引用表的行末标识符,来实现水印信息的间接嵌入。实验结果表明,该算法水印容量能满足数字版权保护的要求,隐蔽性好,能抵抗统计等攻击。

Digital watermarking algorithm based on structure of PDF document

With the rapid development of digital product,the copyright protection of PDF documents has become a crucial research topic in the information security field.This paper analyzed the structure of PDF documents and the relative digital watermarking algorithms.In order to solve the problem that some large capacity text watermarking algorithms increase the size of the document,the authors proposed a digital watermarking algorithm based on the structure of PDF document.Considering the characteristics that end-of-line marker cannot be shown in the document,this algorithm managed to embed watermark through replacing end-of-line markers of the cross-reference table with a fixed format.The experimental results show that,the proposed algorithm can not only reach the standard of watermark capacity required by digital copyright protection,but also has good concealment and can resist statistics attack as well.