(VB.NET) CMS Sign Hash

Demonstrates how to use the SignHashENC method to sign a pre-computed hash. This method creates a CMS signature (PKCS7 detached signature).

This example requires Chilkat v9.5.0.90 or later.

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' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

Dim crypt As New Chilkat.Crypt2

' Create the hash to be signed...
crypt.HashAlgorithm = "sha256"
crypt.EncodingMode = "base64"
crypt.Charset = "utf-8"
' Create the SHA256 hash of a string using the utf-8 byte representation.
' Return the hash as base64.
Dim base64Hash As String = crypt.HashStringENC("This is the string to be hashed")

' Load a certificate for signing.
Dim cert As New Chilkat.Cert
Dim success As Boolean = cert.LoadPfxFile("qa_data/pfx/cert_test123.pfx","test123")
If (success = False) Then
    Debug.WriteLine(cert.LastErrorText)
    Exit Sub
End If

crypt.SetSigningCert(cert)

' Sign the hash to create a base64 CMS signature (which does not contain the original data).
' We can get the signature in a single line of base64 by specifying "base64", or 
' we can get multi-line base64 by specifying "base64_mime".
crypt.EncodingMode = "base64_mime"
Dim base64CmsSig As String = crypt.SignHashENC(base64Hash,"sha256","base64")
If (crypt.LastMethodSuccess = False) Then
    Debug.WriteLine(crypt.LastErrorText)
    Exit Sub
End If


' Note: In the above call to SignHashENC, the encoding of the returned CMS signature is specified by the EncodingMode property.
' However, the encoding of the passed-in hash is indicated by the 3rd argument.

Debug.WriteLine("CMS Signature: " & base64CmsSig)