Verify Pdf hasn't modified after adding signature?.

[ios man]

Hello,

I am using PDF component for adding digital signatures to the pdf document. 

Here is how I am adding the signature

   PdfLoadedDocument document = new PdfLoadedDocument("DigitalSignaturee2.pdf");

            PdfLoadedPage page = document.Pages[0] as PdfLoadedPage;

            //Creates a signature field.

            PdfSignatureField signatureField = new PdfSignatureField(page, "SignatureField");

            signatureField.Bounds = new RectangleF(0, 0, 100, 100);

            signatureField.Signature = new PdfSignature(document, page, new PdfCertificate(@"C:\Users\Public\Documents\Syncfusion\ASP.NET MVC - EJ2\16.3.0.21\App_Data\PDF\PDF.pfx", "syncfusion"), "SignatureField");

            signatureField.Signature.Reason = "I am author of this document";

            document.Form.Fields.Add(signatureField);

            document.Save();

            //Closes the document

            document.Close(true);

I can get the document certificate as of volume 4 release. But how can I verify that document hasn't modified after the signature was added. 

Here is the code for the signature retrieval.

PdfLoadedDocument loadedDocument = new PdfLoadedDocument("DigitalSignaturee2.pdf");

            //Gets the page of the document

            PdfLoadedPage page1 = loadedDocument.Pages[0] as PdfLoadedPage;

         

            PdfLoadedSignatureField field2 = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField;

         

            //Get PDF Certificate instance from signature field

            PdfCertificate certificate = field2.Signature.Certificate;

            //Get the certificate details

            string subjectName = certificate.SubjectName;

            string issuerName = certificate.IssuerName;

thanks

iosman

[Sowmiya Loganathan]

Hi iosman,  

Thank you for contacting Syncfusion support.  

We can verify whether PDF document has been modified or not by using “IsDocumentProperty” of PdfLoadedSignatureField. Please refer the below documentation link for more details, 

https://help.syncfusion.com/file-formats/pdf/working-with-digitalsignature#digital-signature-validation  

We have checked with the provided code snippet and noticed that you have adding the signature field to PDF form after adding the signature in it. While doing this resultant PDF get changed, so we have modified the code snippet and please find the same from below, 

//Load PDF document  

PdfLoadedDocument document = new PdfLoadedDocument("DigitalSignaturee2.pdf"); 

 

//Get loaded page 

PdfLoadedPage page = document.Pages[0] as PdfLoadedPage; 

 

//Creates a signature field 

PdfSignatureField signatureField = new PdfSignatureField(page, "SignatureField"); 

 

//Add siganture  

signatureField.Bounds = new RectangleF(0, 0, 100, 100); 

signatureField.Signature = new PdfSignature(document, page, new PdfCertificate(@"PDF.pfx", "syn 

signatureField.Signature.Reason = "I am author of this document"; 

 

//Save the document  

document.Save(); 

//Closes the document 

document.Close(true); 

 

//Load the documet  

PdfLoadedDocument loadedDocument = new PdfLoadedDocument("DigitalSignaturee2.pdf"); 

 

//Gets the page of the document 

PdfLoadedPage page1 = loadedDocument.Pages[0] as PdfLoadedPage; 

 

//Gets the first signature field of the PDF document. 

PdfLoadedSignatureField field2 = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField; 

 

//Validate signature and get the validation result 

PdfSignatureValidationResult result = field2.ValidateSignature(); 

 

//Get value whether document is modified or not  

bool isDocumentModified = result.IsDocumentModified; 

Sample Link: https://www.syncfusion.com/downloads/support/forum/148883/ze/DigitalSignatureSample1551523105  

Please try the above sample in your end and let us know the result.  

Regards, 

Sowmiya Loganathan 

[ios man]

Hello,

I am using PDF component for adding digital signatures to the pdf document. 

Here is how I am adding the signature

   PdfLoadedDocument document = new PdfLoadedDocument("DigitalSignaturee2.pdf");

            PdfLoadedPage page = document.Pages[0] as PdfLoadedPage;

            //Creates a signature field.

            PdfSignatureField signatureField = new PdfSignatureField(page, "SignatureField");

            signatureField.Bounds = new RectangleF(0, 0, 100, 100);

            signatureField.Signature = new PdfSignature(document, page, new PdfCertificate(@"C:\Users\Public\Documents\Syncfusion\ASP.NET MVC - EJ2\16.3.0.21\App_Data\PDF\PDF.pfx", "syncfusion"), "SignatureField");

            signatureField.Signature.Reason = "I am author of this document";

            document.Form.Fields.Add(signatureField);

            document.Save();

            //Closes the document

            document.Close(true);

I can get the document certificate as of volume 4 release. But how can I verify that document hasn't modified after the signature was added. 

Here is the code for the signature retrieval.

PdfLoadedDocument loadedDocument = new PdfLoadedDocument("DigitalSignaturee2.pdf");

            //Gets the page of the document

            PdfLoadedPage page1 = loadedDocument.Pages[0] as PdfLoadedPage;

         

            PdfLoadedSignatureField field2 = loadedDocument.Form.Fields[0] as PdfLoadedSignatureField;

         

            //Get PDF Certificate instance from signature field

            PdfCertificate certificate = field2.Signature.Certificate;

            //Get the certificate details

            string subjectName = certificate.SubjectName;

            string issuerName = certificate.IssuerName;

thanks

iosman

thanks for the information.

[Sarasilmiya Shahul Hameed]

Hi iosman, 

  

Most welcome. Please get back to us if you need further assistance. 

  

Regards, 

Sara