Android™

Send an Email with a Digital Signature

Demonstrates the Chilkat Email.SendSigned property. Set it to true to have the email sent with a digital signature (the default is false). Signing also requires a certificate with access to its private key. This example loads that certificate (and its private key) from a PFX file with Cert.LoadPfxFile, supplies it via SetSigningCert, and enables signed sending.

Background: Signing is the mirror image of encrypting. To encrypt for a recipient you use their public certificate; to sign you use your own private key, and recipients verify with your public certificate. A signature does not hide the message — a signed email is still readable by anyone — but it proves who sent it and guarantees the content was not tampered with. A PFX (also called PKCS#12, .pfx or .p12) is a password-protected file that bundles a certificate together with its private key, making it a convenient single-file source for signing credentials.

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// Important: Don't forget to include the call to System.loadLibrary
// as shown at the bottom of this code sample.
package com.test;

import android.app.Activity;
import com.chilkatsoft.*;

import android.widget.TextView;
import android.os.Bundle;

public class SimpleActivity extends Activity {

  private static final String TAG = "Chilkat";

  // Called when the activity is first created.
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    boolean success = false;

    //  Demonstrates the Email.SendSigned property with a full signing setup.  Set SendSigned
    //  to true to have the email sent with a digital signature.  Signing requires a certificate
    //  with access to its private key, which we load here from a PFX (.pfx / .p12) file.

    CkEmail email = new CkEmail();
    email.put_Subject("Signed email");
    email.put_Body("This message will be sent with a digital signature.");
    email.put_From("alice@example.com");
    email.AddTo("Bob","bob@example.com");

    //  Load the signing certificate (including its private key) from a PFX file.
    //  The 2nd argument is the PFX password.
    CkCert cert = new CkCert();
    success = cert.LoadPfxFile("qa_data/certs/signer.pfx","pfx_password");
    if (success == false) {
        Log.i(TAG, cert.lastErrorText());
        return true;
        }

    //  Provide the signing certificate.
    success = email.SetSigningCert(cert);
    if (success == false) {
        Log.i(TAG, email.lastErrorText());
        return true;
        }

    //  Request that the email be sent with a digital signature.
    email.put_SendSigned(true);

    Log.i(TAG, "SendSigned = " + String.valueOf(email.get_SendSigned()));

    //  Note: The path "qa_data/certs/signer.pfx" is a relative local filesystem path,
    //  relative to the current working directory of the running application.

  }

  static {
      System.loadLibrary("chilkat");

      // Note: If the incorrect library name is passed to System.loadLibrary,
      // then you will see the following error message at application startup:
      //"The application <your-application-name> has stopped unexpectedly. Please try again."
  }
}