![]() non-repudiation- we want assurance that the author can’t deny his or her authorship.the authenticity of the document- we want assurance that the author of the document is who we think it is (and not somebody else),.the integrity of the document- we want assurance that the document hasn’t been changed somewhere in the workflow,. ![]() Nowadays, we can use digital signatures to ensure: On different places in the workflow, at different moments in time, the document can be altered, be it voluntary, for instance to add an extra signature, involuntary, for example due to a transmission error, or deliberately, if somebody wants to create a forgery from the original document.įor centuries, we’ve tried to solve this problem by putting a so-called ‘wet ink signature’ on paper. Furthermore, this document probably has to be mailed to, viewed and stored by different parties. You don’t want people to deny the commitments they’ve written down. Such a document may contain important information about rights and obligations, in which case you need to ensure its authenticity. In this paper we’ll focus on one specific aspect of PDF files that makes the choice for PDF over any other document format a no-brainer: digital signatures. Because of this, PDF has become the preferred document format of choice in many professional sectors and industries. Plenty of functionality has been added to the PDF format over the years. In the years that followed, an abundance of new tools from Adobe as well as from third party software vendors emerged, and the PDF specification was -and still is- very much alive. PDF became renowned as the format that could be trusted to ensure a consistent output, be it on screen or in print. This mission was set forth in the Camelot paper, and it was accomplished with the first publication of the Portable Document Format Reference (Adobe, 1993) and the availability of the first PDF software products created by Adobe. ![]() The technology was conceived with the goal “to provide a collection of utilities, applications, and system software so that a corporation can effectively capture documents from any application, send electronic versions of these documents anywhere, and view and print these documents on any machines.” (Warnock, 1991) Why we need PDF The main rationale for PDF used to be viewing and printing documents in a reliable way. Both Java and .NET (C#) examples can be found in the following addendum to the Digital Signatures eBook. However, we have updated the digital signature examples to apply to the latest releases of iText 7. NOTE: The following Digital Signatures eBook was originally written for iText 5/iTextSharp and although many of the described concepts and operations are still relevant and transferable to iText 7, the included code examples are outdated. ![]()
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