Research Of Electronic Seal System Based On PDF

The paper introduces the concept and significance of electronic seal system at first and then illustrates the situation of this research field at home and abroad. It puts forward the directions this case focuses on according to the blank and defect of electronic seal system at present. The frame of electronic seal system based on PDF is designed on the basis of the academic study and analysis on technology of cryptology, digital signature and digital watermark. According to the demand of document transmission in E-government in China, it chooses the suitable algorithms of encryption, signature and watermark, and then devises the demonstration of the system.This system is based on Portable Document Format which has developed into the major document format in the Internet information transmission. The article also describes the ideas and the whole process of implementing every module in the system in detail. It can add digital signature and electronic seal to a file of PDF, and then encrypt or decrypt this file by operating the demonstration of this application. The information concerned about signature which is integrated as watermark is embedded in the image of seal instead of being attached with the file. This method can avoid fabricating the seal illegally or juggling the content of the file. The receiver compares the digest in the seal and another digest which is the result of computing the file received. If the two digests are different, it means the file is changed during the transmission. The integrity and non-repudiation of the file is guaranteed in this way. Test results of the application which are provided at the end of the paper demonstrate that this system can not only operate files of PDF successfully but also guarantee security of document transmission.This system is designed based on modular programming and each module connects with each other through interface. Using this design pattern, the system can easily be upgraded and maintained. Friendly interface simplifies the operations, while timestamp is added to enhance security of file transmission. The design of this system fills the blank of electronic seal system based on PDF and realizes the real automation office without paper.