(Visual Basic) Add S/MIME Signature using PFX

Add a digital signature to a MIME message using the certificate + private key from a PFX file.

Download Chilkat MIME ActiveX

Dim mime As New ChilkatMime

Dim success As Long
success = mime.UnlockComponent("Anything for 30-day trial")
If (success = 0) Then
    Text1.Text = Text1.Text & mime.LastErrorText & vbCrLf
    Exit Sub
End If

'  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"
success = cert.LoadPfxFile(pfxFilepath,pfxPassword)
If (success = 0) Then
    Text1.Text = Text1.Text & cert.LastErrorText & vbCrLf
    Exit Sub
End If

mime.SetBodyFromPlainText "This is the plain-text MIME body."

mime.Charset = "utf-8"
mime.Encoding = "quoted-printable"

'  Sign the MIME (adds a PKCS7 detached signature)
success = mime.AddDetachedSignature(cert)
If (success = 0) Then
    Text1.Text = Text1.Text & mime.LastErrorText & vbCrLf
    Exit Sub
End If

'  Save the S/MIME to a file.
success = mime.SaveMime("/temp/signedMime.txt")
If (success = 0) Then
    Text1.Text = Text1.Text & mime.LastErrorText & vbCrLf
    Exit Sub
End If

MsgBox "success!"