Visual Basic 6.0

Send an Email with a Digital Signature

Demonstrates the Chilkat Email.SendSigned property. Set it to true to have the email sent with a digital signature (the default is false). Signing also requires a certificate with access to its private key. This example loads that certificate (and its private key) from a PFX file with Cert.LoadPfxFile, supplies it via SetSigningCert, and enables signed sending.

Background: Signing is the mirror image of encrypting. To encrypt for a recipient you use their public certificate; to sign you use your own private key, and recipients verify with your public certificate. A signature does not hide the message — a signed email is still readable by anyone — but it proves who sent it and guarantees the content was not tampered with. A PFX (also called PKCS#12, .pfx or .p12) is a password-protected file that bundles a certificate together with its private key, making it a convenient single-file source for signing credentials.

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Visual Basic 6.0

Dim success As Long
success = 0

'  Demonstrates the Email.SendSigned property with a full signing setup.  Set SendSigned
'  to true to have the email sent with a digital signature.  Signing requires a certificate
'  with access to its private key, which we load here from a PFX (.pfx / .p12) file.

Dim email As New ChilkatEmail
email.Subject = "Signed email"
email.Body = "This message will be sent with a digital signature."
email.From = "alice@example.com"
success = email.AddTo("Bob","bob@example.com")

'  Load the signing certificate (including its private key) from a PFX file.
'  The 2nd argument is the PFX password.
Dim cert As New ChilkatCert
success = cert.LoadPfxFile("qa_data/certs/signer.pfx","pfx_password")
If (success = 0) Then
    Debug.Print cert.LastErrorText
    Exit Sub
End If

'  Provide the signing certificate.
success = email.SetSigningCert(cert)
If (success = 0) Then
    Debug.Print email.LastErrorText
    Exit Sub
End If

'  Request that the email be sent with a digital signature.
email.SendSigned = 1

Debug.Print "SendSigned = " & email.SendSigned

'  Note: The path "qa_data/certs/signer.pfx" is a relative local filesystem path,
'  relative to the current working directory of the running application.