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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Java

import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    boolean success = false;

    CkMime mime = new CkMime();
    success = mime.SetBodyFromPlainText("This message will be signed.");
    if (success == false) {
        System.out.println(mime.lastErrorText());
        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";
    CkCert cert = new CkCert();
    success = cert.LoadPfxFile("qa_data/signer.pfx",pfxPassword);
    if (success == false) {
        System.out.println(cert.lastErrorText());
        return;
        }

    //  Create an S/MIME detached signature.  The object becomes a multipart/signed entity with the
    //  original content and a separate signature part.
    success = mime.AddDetachedSignature(cert);
    if (success == false) {
        System.out.println(mime.lastErrorText());
        return;
        }

    success = mime.SaveMime("qa_output/signed.eml");
    if (success == false) {
        System.out.println(mime.lastErrorText());
        return;
        }

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