关键词: PDF, 渲染模式, 字体饱和度, 版权归属, 真伪鉴定

Abstract:

In order to solve the problems like document tampering that is leaded by multi-channel information dissemination on the Internet and the copyright of documents,this paper proposes a new algorithm that is based on the text format by analyzing the structure and content flow characteristics of PDF (Portable Document Format).The Kerckhoffs safety criteria and the digital signature algorithm are adopted to solve the problem of the copyright and to identify document tampering effectively.The author put the invisible watermark in the PDF document as a portable digital signature,thus modifying the properties of saturation without damage to the structure of the document through selective modification and adding related attributes to achieve the purpose of putting watermark in the document.Checking the watermark from the PDF document and the comparison with the original watermark can identify both the authenticity of a document and the copyright.The experimental result shows that the algorithm has good transparency and robustness,and has a larger capacity of watermark,which helps identify if the document has been tampered.

Key words: PDF;rendering mode;saturation characteristics;original;check the consistency