PHP Extension

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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<?php

include("chilkat.php");

$success = 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.

$email = new CkEmail();
$email->put_Subject('Signed email');
$email->put_Body('This message will be sent with a digital signature.');
$email->put_From('alice@example.com');
$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.
$cert = new CkCert();
$success = $cert->LoadPfxFile('qa_data/certs/signer.pfx','pfx_password');
if ($success == false) {
    print $cert->lastErrorText() . "\n";
    exit;
}

//  Provide the signing certificate.
$success = $email->SetSigningCert($cert);
if ($success == false) {
    print $email->lastErrorText() . "\n";
    exit;
}

//  Request that the email be sent with a digital signature.
$email->put_SendSigned(true);

print 'SendSigned = ' . $email->get_SendSigned() . "\n";

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

?>