Add a Detached Signature with a Separate Private Key

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Demonstrates the Chilkat Mime.AddDetachedSignaturePk method, which creates a detached signature using a signer certificate and its separately supplied private key. The first argument is the Cert and the second is the PrivateKey.

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: Sometimes the certificate and its private key live apart — a .cer alongside a PEM key file, for instance — rather than bundled in a single PFX. This method pairs them explicitly for signing, whereas AddDetachedSignature expects a Cert that already provides its key. The result is the same multipart/signed message.

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bool success = false;

Chilkat.Mime mime = new Chilkat.Mime();
success = mime.SetBodyFromPlainText("This message will be signed.");
if (success == false) {
    Debug.WriteLine(mime.LastErrorText);
    return;
}

//  Load the certificate and its private key separately.
Chilkat.Cert cert = new Chilkat.Cert();
success = cert.LoadFromFile("qa_data/signer.cer");
if (success == false) {
    Debug.WriteLine(cert.LastErrorText);
    return;
}

Chilkat.PrivateKey privKey = new Chilkat.PrivateKey();
success = privKey.LoadPemFile("qa_data/signer_privkey.pem");
if (success == false) {
    Debug.WriteLine(privKey.LastErrorText);
    return;
}

//  Create a detached signature when the certificate and private key are supplied separately.  The
//  1st argument is the signer certificate and the 2nd is its private key.
success = mime.AddDetachedSignaturePk(cert,privKey);
if (success == false) {
    Debug.WriteLine(mime.LastErrorText);
    return;
}

success = mime.SaveMime("qa_output/signed.eml");
if (success == false) {
    Debug.WriteLine(mime.LastErrorText);
    return;
}

Debug.WriteLine("Detached signature added.");