Dart

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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Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // 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.

  final email = CkEmail();
  email.subject = 'Signed email';
  email.body = 'This message will be sent with a digital signature.';
  email.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.
  final cert = CkCert();
  try {
    cert.loadPfxFile('qa_data/certs/signer.pfx', 'pfx_password');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Provide the signing certificate.
  try {
    email.setSigningCert(cert);
  } on ChilkatException catch (e) {
    print(e.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.
}