(Visual Basic 6.0) Create PKCS7 Attached/Opaque Signature (S/MIME)

Create an S/MIME message with a PKCS7 attached/opaque signature.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

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

Dim mime As New ChilkatMime

' Load a certificate w/ private key for signing.
' There are many ways of getting a certificate object:
' from a pfx file, from .cer and private-key files, from the
' Windows registry-based certificate stores, etc.
' Load a PFX file into a certificate object.
Dim cert As New ChilkatCert
Dim pfxFilepath As String
pfxFilepath = "pfxFiles/something.pfx"
Dim pfxPassword As String
pfxPassword = "secret"
Dim success As Long
success = cert.LoadPfxFile(pfxFilepath,pfxPassword)
If (success = 0) Then
    Debug.Print cert.LastErrorText
    Exit Sub
End If

' Create a very simple MIME message to be signed:
success = mime.AddHeaderField("Subject","This is a test")
success = mime.AddHeaderField("MyCustomHeader","abc123")
mime.ContentType = "text/plain"
mime.SetBody "This is a plain-text body."

' Examine the MIME prior to signing:
Debug.Print "--- MIME prior to signing ---"
Debug.Print mime.GetMime()

' The MIME prior to signing looks like this:
' -------------------------------------------------------------------------------

' Subject: This is a test
' MyCustomHeader: abc123
' Content-Type: text/plain
' 
' This is a plain-text body.

' -------------------------------------------------------------------------------

' The default hash algorithm used in the signing process is "SHA1".
' To change it, set the SigningHashAlg property:
mime.SigningHashAlg = "SHA256"

' Convert the MIME to PKCS7 signed-data.
success = mime.ConvertToSigned(cert)
If (success = 0) Then
    Debug.Print mime.LastErrorText
    Exit Sub
End If

' Examine the signed MIME
Debug.Print "--- MIME converted to PKCS7 signed-data ---"
Debug.Print mime.GetMime()

' The MIME after signing looks like this:
' -------------------------------------------------------------------------------

' Subject: This is a test
' MyCustomHeader: abc123
' Content-Disposition: attachment; filename="smime.p7m"
' Content-Transfer-Encoding: base64
' Content-Type: application/x-pkcs7-mime;
'  name="smime.p7m"; smime-type="signed-data"
' 
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' 

' ------------------------------------------------------------------------------