Dart

Add a Detached Signature with a Separate Private Key

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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Dart

import 'package:chilkat/chilkat.dart';

void main() {
  final mime = CkMime();
  try {
    mime.setBodyFromPlainText('This message will be signed.');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Load the certificate and its private key separately.
  final cert = CkCert();
  try {
    cert.loadFromFile('qa_data/signer.cer');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final privKey = CkPrivateKey();
  try {
    privKey.loadPemFile('qa_data/signer_privkey.pem');
  } on ChilkatException catch (e) {
    print(e.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.
  try {
    mime.addDetachedSignaturePk(cert, privKey);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  try {
    mime.saveMime('qa_output/signed.eml');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('Detached signature added.');
}