Android™

Use RSAES-OAEP Padding for Encrypted Email

Demonstrates the Chilkat Email.OaepPadding property, which selects the RSA encryption scheme used when encrypting email. The default is false, which selects RSAES PKCS1-v1_5; setting it to true selects RSAES-OAEP. This affects the RSA key-encryption step used for S/MIME encryption — it does not change the symmetric content-encryption algorithm chosen by Pkcs7CryptAlg. This example enables OAEP padding.

Background: Recall that S/MIME encrypts the message body with a one-time symmetric key, then encrypts that key with RSA. "Padding" is how the key bytes are formatted before RSA is applied. The older PKCS1-v1_5 padding has known theoretical weaknesses, while RSAES-OAEP adds randomness and a hash-based construction that is provably more secure and is the modern recommendation. Both endpoints must agree, so a recipient's software has to support OAEP to read the message.

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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);

    //  Demonstrates the Email.OaepPadding property, which selects the RSA encryption scheme
    //  used when encrypting email.  The default is false (RSAES PKCS1-v1_5).  Set it to true
    //  to use RSAES-OAEP.  This affects only the RSA key-encryption step, not the symmetric
    //  content-encryption algorithm selected by Pkcs7CryptAlg.

    CkEmail email = new CkEmail();
    email.put_Subject("Encrypted with RSAES-OAEP");
    email.put_Body("This message uses OAEP padding for the RSA key encryption.");

    //  Use RSAES-OAEP instead of the older PKCS1-v1_5 scheme.
    email.put_OaepPadding(true);

    Log.i(TAG, "OaepPadding = " + String.valueOf(email.get_OaepPadding()));

  }

  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."
  }
}