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Topic: Validating Digital Signatures from a FORM submit to a Web Server
Conf: (P-PDF) Developers, Msg: 79335
From: mwahaj
Date: 1/11/2003 12:26 AM

Hi All,

How can I verify the Digital Signature present on an E-Form containing submitted by a user over internet using FDF toolkit.

I am trying to extract signatures which are submitted using FDF. I have a web server containing a PDF form, user fills the form, apply digital signature and press submit button. On the server ExtractAppendSaves(file) function is called which extract the changes made in the form and saves in a File. In order to create the PDF document, I appended the File Contents (containing the signature and other entries) to the template PDF thus populating the items. If I open this PDF and try to verify the signature using Adobe Acrobat, I get an error “Signature is Invalid. The document has been altered since it was signed”, which I think is not right. How can I check that whether the contents submitted by the user have been changed or not. I am also using a third party Java toolkit which can extract Certificates and digital signatures out of a PDF doc and it is also specifying that signature is not valid where as no one has modified it during transit. I am using Adobe Acrobat 5.0 (5.0.5) and I am submitting while I am viewing the form inside IE

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