Dart

Check if a MIME Entity is Signed (S/MIME)

Demonstrates the Chilkat Mime.IsSigned method, which returns whether the entity is a complete CMS/PKCS #7 signed S/MIME wrapper, including detached multipart/signed and opaque forms. It takes no arguments.

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

Background: Before verifying a signature you need to know one is present, and this is the check. A signed S/MIME message comes in two shapes — detached (multipart/signed, signature alongside the content) and opaque (application/pkcs7-mime, content wrapped inside the signature) — and this recognizes both. Follow a true result with Verify.

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Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // Demonstrates the Mime.IsSigned method, which returns whether the entity is a complete CMS/PKCS #7 signed S/MIME wrapper.  It takes no arguments.

  final mime = CkMime();
  try {
    mime.loadMimeFile('qa_data/signed.eml');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  if (mime.isSigned()) {
    print('This is a signed S/MIME message.');
  } else {
    print('This is not a signed S/MIME message.');
  }
}