Swift

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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func chilkatTest() {
    var success: Bool = false

    //  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.

    let email = CkoEmail()!
    email.subject = "Signed email"
    email.body = "This message will be sent with a digital signature."
    email.from = "alice@example.com"
    email.add(to: "Bob", emailAddress: "bob@example.com")

    //  Load the signing certificate (including its private key) from a PFX file.
    //  The 2nd argument is the PFX password.
    let cert = CkoCert()!
    success = cert.loadPfxFile(path: "qa_data/certs/signer.pfx", password: "pfx_password")
    if success == false {
        print("\(cert.lastErrorText!)")
        return
    }

    //  Provide the signing certificate.
    success = email.setSigningCert(cert: cert)
    if success == false {
        print("\(email.lastErrorText!)")
        return
    }

    //  Request that the email be sent with a digital signature.
    email.sendSigned = true

    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.

}