Research Of The PDF Document's Building And The Originality Identify

PDF format document currently has become numeral to turn an information in fact of an industry standard, it of across medium, cross-platform, safety to make it an application in the network more and more extensive, as to it's study to seem to be day by day important.How born PDF document's less in local research is, this text inquiried into the born method of PDF document, introduced a PDF document a format in detail, characteristics and application of PDF document, passed a PDF document a solid example analysis it to constitute structure;Pass experiment elucidation how to make use of to open the source software born PDF document of the iTextSharp.In the actual usage PDF the process of the document, how prevent°from a PDF document being distort is also a count for much research topic, this text we can add a marking on the PDF document, if the value of this marking took place variety and then explain this text file is distorted, but this document wasn't the most original document.This text passes to make use of MD5 valueses to carry on an original sex verification to the PDF text file, MD5's values' biggest characteristics is to take MD5 codeses to a document, and it this code be unique, if the document is change to move, it the MD5 codeses will also take place variety, so we as long as check the MD5 codeses of PDF document can prove whether the PDF document use is true and original or not.The concrete method contains 2 kinds, 1 kind is compute its MD5 values towards release of PDF document, then direct MD5 codes also together with the PDF document together releases, so other customers can pass to compute its MD5 codeseses to confirm the reliability of text file at the time of getting a PDF document.Because the PDF document release of increase, need to build up a website and database to exclusively release and deposit PDF document and MD5 codeses, so carry out still very easy of.Being like to face to public organization can adopt this kind of way, like government agency, court, listed company...etc..The second is the way of thinking which uses numerical watermark, we can write this MD5 to 1 of document to conceal area, the general binary system document format has document head and document body part, document tail three parts, and the document head, tail'be what customer could not see, generally will also reserve a part of words to reduce expenses in hereafter expand, or can at document head the data which write in special marking.Pass the analysis to the front PDF document format, this MD5 write in the document tail.Hence flow the calculation MD5 values to the PDF document, then flow that document and MD5 to be worth to write hard drive together, become a PDF document which added MD5 values.The document can normally open with usage, and the other people can't see add, either of this MD5 values., Observed operation PDF a document through an experiment as to it's under the different environment the influence of the MD5 codeses.Pass an experiment conclusion:The exploitation opens source software iTtextSharp can very expediently born PDF document, can also nicely support Chinese.Make use of the MD5 codeses can verify originality and reliability of a PDF document, but PDF document as long as don't change it, it of the MD5 codeses list in the experiment of operation environment's being next will not change.Put forward on this foundation how to use the strategy of this text method, so this text lowers to transact cost to have actual meaning to the our country usage PDF document.