I need help - I can help - How do I detect that a PDF has a digital signature

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How do I detect that a PDF has a digital signature

Printed From: Debenu Quick PDF Library - PDF SDK Community Forum
Category: For Users of the Library
Forum Name: I need help - I can help
Forum Description: Problems and solutions while programming with the Debenu Quick PDF Library and Debenu PDF Viewer SDK
URL: http://www.quickpdf.org/forum/forum_posts.asp?TID=2529
Printed Date: 08 Jan 26 at 5:11AM
Software Version: Web Wiz Forums 11.01 - http://www.webwizforums.com

Topic: How do I detect that a PDF has a digital signature

Posted By: AnnD
Subject: How do I detect that a PDF has a digital signature
Date Posted: 11 Feb 13 at 9:28PM

In my application I am adding some modifications to a PDF file. I don't want to invalidate the digital signature, so I want to skip the modification if a file has a digital signature. How do I determine if the file has a digital signature using the QuickPDF api?

Replies:

Posted By: Ingo
Date Posted: 12 Feb 13 at 10:14AM

Hi Ann!

That's not possible with QuickPDF-functionality:

http://www.quickpdflibrary.com/faq/verify-a-signature.php - http://www.quickpdflibrary.com/faq/verify-a-signature.php

What i can imagine is ...

Read the complete pdf-content into a string and check for

special tags having to do with signatures.

Before you should have a look (with notepad) into a pdf

without and with signature to see the differences.

Only an idea ... perhaps it works ;-)

Cheers and welcome here,

Ingo

Posted By: AndrewC
Date Posted: 18 Feb 13 at 7:10AM

You may want to try the following code

bool hasSig = false;

for (int i = 1; i <= QP.FormFieldCount(); i++)

if (QP.GetFormFieldType(i) == 6) // FormFieldType = Signature

hasSig = true;

Posted By: Ingo
Date Posted: 18 Feb 13 at 1:41PM

Good to know.

Should be something for the guides or samples?

Nobody will have the idea to check the formfield-types ;-)

Cheers, Ingo