How to concatenate the signed hash to the original PDF?

[Winanjaya]

Hi,

I have .p7s file,  How to concatenate the signed hash to the original PDF?

Please help

Thanks

[Praveenkumar H]

Hi PTDigtial 

We cannot directly embed the .p7s file in PDF document, since digital signature involves the following step. 

1.       Get the hash from the PDF document. 

2.       Sign the hash of the PDF document in local or from signature service. 

3.       Finally embed singed signature into the PDF document. 

So can you please provide more details (code snippet or samples) about how you generated .p7s file so that we can provide exact solution to your requirement. 

Regards, 

Praveen 

[Winanjaya]

so the hash of PDF will be sent to EJBCA?.. how to get PDF's hash value?

[Praveenkumar H]

  

Hi Winanjaya 

Yes the hash of the PDF document need to be send to signature service, you can get the hash of the PDF document using below code snippet. 

FileStream documentStream = new FileStream("PDF_Succinctly.pdf ", FileMode.Open, FileAccess.Read); 

 

//Load the existing PDF document 

 

PdfLoadedDocument document = new PdfLoadedDocument(documentStream); 

 

//Creates a digital signature 

 

PdfSignature signature = new PdfSignature(document, document.Pages[0], null, "DigitalSignature"); 

 

signature.ComputeHash += Signature_ComputeHash; 

 

MemoryStream ms = new MemoryStream(); 

 

document.Save(ms); 

 

document.Close(true); 

 

private static void Signature_ComputeHash1(object sender, PdfSignatureEventArgs ars) 

{ 

//Get the document bytes and calculate the hash of the bytes. 

byte[] hash = System.Security.Cryptography.SHA512.Create().ComputeHash(ars.Data); 

 

} 

Regards, 

Praveen 

[Winanjaya]

How about if the pdf password protected?

[Moorthy Karunanithi]

Hi Winanjaya, 

How about if the pdf password protected?

Yes, we can use the same code for the password-protected PDF documents too.

Regards, 

Moorthy K