(Android™) JWE using A256GCMKW

This example demonstrates creating a JCE with AES GCM key wrap.

Chilkat Android™ Downloads Android™ Java Libraries Android C/C++ Libraries

// 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);

    // This requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    boolean success;
    String plaintext = "My text to enrypt";

    CkJwe jwe = new CkJwe();

    // First build the JWE Protected Header: 

    //         {
    //             "alg": "A256GCMKW",
    //             "kid": "18ec08e1-bfa9-4d95-b205-2b4dd1d4321d",
    //             "tag": "kfPduVQ3T3H6vnewt--ksw",
    //             "iv": "KkYT0GX_2jHlfqN_",
    //             "enc": "A128CBC-HS256"
    //         }

    CkJsonObject jweProtHdr = new CkJsonObject();
    jweProtHdr.AppendString("alg","A256GCMKW");
    // kid is optional
    jweProtHdr.AppendString("kid","18ec08e1-bfa9-4d95-b205-2b4dd1d4321d");
    // tag is optional
    jweProtHdr.AppendString("tag","kfPduVQ3T3H6vnewt--ksw");
    jweProtHdr.AppendString("enc","A256GCM");
    // the iv should be 16 random chars.
    CkPrng prng = new CkPrng();
    jweProtHdr.AppendString("iv",prng.randomString(16,true,true,true));
    jwe.SetProtectedHeader(jweProtHdr);

    Log.i(TAG, "JWE Protected Header: " + jweProtHdr.emit());
    Log.i(TAG, "--");

    // Given that we have 256-bit AES, our key should be 32 bytes.
    // The ascii string here is 32 bytes, therefore the 2nd arg is "ascii" to use these
    // ascii chars directly as the key.
    String aesWrappingKey = "2baf4f730f5e4542b428593ef9cceb0e";
    jwe.SetWrappingKey(0,aesWrappingKey,"ascii");

    // Encrypt and return the JWE:
    String strJwe = jwe.encrypt(plaintext,"utf-8");
    if (jwe.get_LastMethodSuccess() != true) {
        Log.i(TAG, jwe.lastErrorText());
        return;
        }

    // Show the JWE we just created:
    Log.i(TAG, strJwe);

    // Decrypt the JWE that was just produced.
    // 1) Load the JWE.
    // 2) Set the AES wrapping key.
    // 3) Decrypt.
    CkJwe jwe2 = new CkJwe();
    success = jwe2.LoadJwe(strJwe);
    if (success != true) {
        Log.i(TAG, jwe2.lastErrorText());
        return;
        }

    // Set the AES wrap key.  Important to use "ascii"
    jwe2.SetWrappingKey(0,aesWrappingKey,"ascii");

    // Decrypt.
    String originalPlaintext = jwe2.decrypt(0,"utf-8");
    if (jwe2.get_LastMethodSuccess() != true) {
        Log.i(TAG, jwe2.lastErrorText());
        return;
        }

    Log.i(TAG, "original text: ");
    Log.i(TAG, originalPlaintext);

  }

  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."
  }
}