PdfDeferredSignatureBuilder Class

Allows you to build a signature for a document hash.

Namespace: DevExpress.Pdf

Assembly: DevExpress.Pdf.v20.2.Core.dll

NuGet Package: DevExpress.Pdf.Core

NuGet Packages: DevExpress.Pdf.Core, DevExpress.WindowsDesktop.Pdf.Core

Declaration

C#

public class PdfDeferredSignatureBuilder :
    PdfSignatureBuilder

VB.NET

Public Class PdfDeferredSignatureBuilder
    Inherits PdfSignatureBuilder

Remarks

You can build a signature for a new or existing form field. Use the PdfSignatureFieldInfo object to create a new signature field. Pass the name of an existing field to apply a signature to it.

Pass the PdfDeferredSignatureBuilder object to the PdfDocumentSigner.SignDeferred method to add a signature to the document and obtain the document hash.

The code sample below uses a document hash to apply a signature externally:

C#

using DevExpress.Office.DigitalSignatures;
using DevExpress.Pdf;

using (var signer = new PdfDocumentSigner(File.OpenRead("SignDemo.pdf")))
{
  //Specify the information about the signature metadata:
  var digestCalculator = new DigestCalculator(HashAlgorithmType.SHA256);

  var signerInfo = new ExternalSignerInfo(PdfSignatureType.Pkcs7, 8000, digestCalculator);

  //Create a new form field:
  var fieldInfo = new PdfSignatureFieldInfo(1) { SignatureBounds = new PdfRectangle(10, 10, 100, 100) };

  //Apply the metadata to the form field:
  var builder = new PdfDeferredSignatureBuilder(signerInfo, fieldInfo);

  //Add the signature to the document:
  var deferredSigner = signer.SignDeferred(builder);

  //Obtain the document hash and hash algorithm's object identifier:
  var digest = deferredSigner.HashValue;
  var digestAlgorithmOID = digestCalculator.AlgorithmOid;

  //Generate the signature content to insert into the document:
  byte[] signature = CreateSignature(digest, digestAlgorithmOID);

  //Add the signature contents and save the document to the file:
  deferredSigner.Sign("signed.pdf", signature);
}

static byte[] CreateSignature(byte[] digest, string digestAlgorithmOID)
{
  var signer = new Pkcs7Signer(@"SignDemo.pfx", "dxdemo");
  byte[] signature = signer.BuildSignature(digest, digestAlgorithmOID);
  return signature;
}

VB.NET

Imports DevExpress.Office.DigitalSignatures
Imports DevExpress.Pdf

Using signer = New PdfDocumentSigner(File.OpenRead("SignDemo.pdf"))
  'Specify the information about the signature metadata:
  Dim digestCalculator = New DigestCalculator(HashAlgorithmType.SHA256)

  Dim signerInfo = New ExternalSignerInfo(PdfSignatureType.Pkcs7, 8000, digestCalculator)

  'Create a new form field:
  Dim fieldInfo = New PdfSignatureFieldInfo(1) With {.SignatureBounds = New PdfRectangle(10, 10, 100, 100)}

  'Apply the metadata to the form field:
  Dim builder = New PdfDeferredSignatureBuilder(signerInfo, fieldInfo)

  'Add the signature to the document:
  Dim deferredSigner = signer.SignDeferred(builder)

  'Obtain the document hash and hash algorithm's object identifier:
  Dim digest = deferredSigner.HashValue
  Dim digestAlgorithmOID = digestCalculator.AlgorithmOid

  'Generate the signature content to insert into the document:
  Dim signature() As Byte = CreateSignature(digest, digestAlgorithmOID)

  'Add the signature contents and save the document to the file:
  deferredSigner.Sign("signed.pdf", signature)
End Using

static Byte() CreateSignature(Byte() digest, String digestAlgorithmOID)
  Dim signer = New Pkcs7Signer("SignDemo.pfx", "dxdemo")
  Dim signature() As Byte = signer.BuildSignature(digest, digestAlgorithmOID)
  Return signature

Inheritance

Object

PdfSignatureBuilder

PdfDeferredSignatureBuilder