Generate digital signature in PDF and verify the certificate

Savadamuthu Saravanan

Hi friends! How to generate digital signature in PDF and verify the certificate using private and public key authentication,I am tried 3 days two many ways but not clear explanation,if you know share me. Hopefully SavadaMuthu Saravanan

6 Replies

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Mohamed Abedallah8y ago
Accepted answer
You can use LEADTOOLS to both sign a PDF document using a certificate, and also verify an existing signature in a PDF file.
To sign a file, you can use the PDFFile.SignDocument method. The code looks like this:
PDFFile document = new PDFFile(sourceFileName);
document.SignDocument(destinationFileName, signatureFileName, signaturePassword);
Note that the “signatureFileName” is the file containing the digital signature. This should be a valid PFX file and cannot be null.

To check if there's a signature in an existing PDF file, the code will be similar to this:
private static bool ContainsSignature(string pdfFileName)
{
PDFDocument document = new PDFDocument(pdfFileName);
PDFParsePagesOptions options = PDFParsePagesOptions.Signatures;
document.ParsePages(options, 1, -1);

foreach (PDFDocumentPage page in document.Pages)
{
IList objects = page.Objects;
if (objects != null)
return true;
}
return false;
}
To verify a signature and see if it's valid, there are details in this help topic:
https://www.leadtools.com/help/leadtools/v19/dh/pdf/pdfsignature.html
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Usman Aziz6y ago
You may try the following code which is based on GroupDocs.Signature for .NET API.

Sign Document
using (Signature signature = new Signature("sample.pdf"))
{
    // initialize digital option with certificate file path
    DigitalSignOptions options = new DigitalSignOptions("certificate.pfx")
    {
        // optional: setup image file path
        ImageFilePath = "sample.jpg",

        // set signature position
        Left = 100,
        Top = 100,

        // set
        Password = "1234567890"
    };
    signature.Sign("sampleSigned.pdf", options);
}
Verify Signature
using (Signature signature = new Signature("sample.pdf"))
{
    DigitalVerifyOptions options = new DigitalVerifyOptions("certificate.pfx")
    {
        Comments = "Test comment"
    };
    // verify document signatures
    VerificationResult result = signature.Verify(options);
    if (result.IsValid)
    {
        Console.WriteLine("\nDocument was verified successfully!");
    }
    else
    {
        Console.WriteLine("\nDocument failed verification process.");
    }
}
0
Bharat Vasant7y ago
If you are looking for PDF Digital Signing, my company provides free component and sample web application integration source code working in VS 2015 or VS 2017 complete download and code logic explained:

http://help.signer.digital/digital_signing_and_authentication_from_web_browser.htm
+7
Savadamuthu Saravanan8y ago
How add a self-signed question mark in digital signature using spire dll
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Savadamuthu Saravanan8y ago
Hi sir,

Ths line PdfSignature signature = new PdfSignature(doc, page, digi, "demo"); doc,page run time type error will diplay

In this line signature.Certificated = true; Out of range error display.

If you know give me the solution.

Thank you & Regards
S.Savadamuthu.
0
Leon D8y ago
Generate and verify digital signature is straightforward with Spire.PDF library. You can reference its free version (free spire.pdf dll) from NuGet Package Manager and have a try.

The following guidance might be of help to you:

https://www.e-iceblue.com/Tutorials/Spire.PDF/Spire.PDF-Program-Guide/PDF-Security/Create-Visible-Digital-Signature-in-PDF-with-C-Code.html

https://www.e-iceblue.com/Tutorials/Spire.PDF/Spire.PDF-Program-Guide/Get-and-Verify-Digital-Signature-in-PDF-with-C-Code.html
+2