通过对PDF文档逻辑结构的分析,在不改变原始PDF文档任何显示属性的基础上,提出并设计了一种针对PDF文档的可同时完成完整性验证和版权认证的数字水印算法。该算法根据PDF结构的特点,将各个页面信息流的MD5摘要信息与版权声明信息整合后经AEs加密处理生成密文水印信息,密文水印信息最终通过伪装成PDF文档对象的形式,随机嵌入载体文件中。理论分析及实验结果都证明,该算法具有安全、高效和高冗余空间的优点,并且可同时完成载体的完整性验证与版权认证。
Based on analysis of the logic structure of PDF-type files, a novel digital watermarking algorithm(DWA) is proposed, which could be applied to PDF files' Integrity & Copyright Authorization without any change on visible property of the original PDF file. According to this algorithm, MD5 digest of the data stream in every PDF pages, together with copyright declaration information, is encrypted via AES to get the encrypted watermark information(EWI). Finally, by disguising as a PDF object, EWI is randomly embedded into the carrier file. Theoretical analysis and experiment results show that DWA with advantages of superior security, high efficiency and large redundancy space, could simultaneously accomplish the integrity & copyright authorization.