Java

Add an S/MIME Detached Signature

Demonstrates the Chilkat Mime.AddDetachedSignature method, which creates an S/MIME detached signature. The only argument is the signing Cert, which must have access to its private key. On success the entity becomes a multipart/signed with the content and a separate signature part.

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: A detached signature (multipart/signed) keeps the original content readable alongside a separate signature part — so recipients whose software does not understand S/MIME still see the message, they just cannot verify it. That backward compatibility makes detached the usual choice for signed email. The signer proves authorship with a certificate that carries its private key.

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import com.chilkatsoft.chilkat2.Cert;
import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.Mime;

public class ChilkatExample {

    public static void main(String[] args) {
        Mime mime = new Mime();
        try {
            mime.setBodyFromPlainText("This message will be signed.");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        // Load the signing certificate (which must have access to its private key) from a PFX file.
        // The PFX password should come from a secure source rather than being hard-coded.
        String pfxPassword = "myPfxPassword";
        Cert cert = new Cert();
        try {
            cert.loadPfxFile("qa_data/signer.pfx", pfxPassword);

            // Create an S/MIME detached signature.  The object becomes a multipart/signed entity with the
            // original content and a separate signature part.
            mime.addDetachedSignature(cert);

            mime.saveMime("qa_output/signed.eml");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println("Detached signature added.");
    }
}