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

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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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bool success = false;

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

Chilkat.Mime mime = new Chilkat.Mime();
success = mime.LoadMimeFile("qa_data/signed.eml");
if (success == false) {
    Debug.WriteLine(mime.LastErrorText);
    return;
}

if (mime.IsSigned()) {
    Debug.WriteLine("This is a signed S/MIME message.");
}
else {
    Debug.WriteLine("This is not a signed S/MIME message.");
}