HashAlgorithmType Enum

SECURITY-RELATED CONSIDERATIONS

Using weak or outdated hash algorithms (such as SHA-1) may allow threat actors to manipulate or predict hash values. Use modern, secure alternatives (such as SHA-256 or stronger).

Lists values used to specify the signature’s secure hash algorithm (SHA) type.

Namespace: DevExpress.Office.DigitalSignatures

Assembly: DevExpress.Pdf.v25.2.Core.dll

Declaration

C#

public enum HashAlgorithmType

VB.NET

Public Enum HashAlgorithmType

Members

Name	Description
SHA1	SHA1 hashing algorithm. This type can affect the signature’s integrity, authenticity, and legal validity.
SHA256	SHA256 hashing algorithm.
SHA384	SHA384 hashing algorithm.
SHA512	SHA512 hashing algorithm.

Related API Members

The following properties accept/return HashAlgorithmType values:

• SignatureOptions.DigestMethod
• SignaturePolicy.DigestMethod

Remarks

Pass one of the HashAlgorithmType enumeration values to the Pkcs7Signer object’s constructor to specify the signature’s hashing algorithm.

Example

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

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