B4X

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.

B4X

Dim success As Boolean = False

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

Dim crypt As ChilkatCrypt2
crypt.Initialize("crypt")

'  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 ChilkatCert
cert.Initialize("cert")
success = cert.LoadPfxFile("qa_data/pfx/cert_test123.pfx", "test123")
If success = False Then
    Log(cert.LastErrorText)
    Return
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
    Log(crypt.LastErrorText)
    Return
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.

Log("CMS Signature: " & base64CmsSig)