(Android™) JWE with Binary Data

Demonstrates how to create a JWE that contains a binary payload (such as a JPG image).

Note: This example requires Chilkat v9.5.0.66 or greater.

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.

    // Note: This example requires Chilkat v9.5.0.66 or greater.

    boolean success;

    // Load a JPG file that will be the JWE payload.
    CkBinData jpgBytes = new CkBinData();
    success = jpgBytes.LoadFile("qa_data/jpg/starfish.jpg");
    // Make sure your app checks the success/failure of the call to LoadFile..
    Log.i(TAG, "Original JPG size = " + String.valueOf(jpgBytes.get_NumBytes()));

    CkJwe jwe = new CkJwe();

    CkJsonObject jweProtHdr = new CkJsonObject();
    jweProtHdr.AppendString("alg","A128KW");
    jweProtHdr.AppendString("enc","A128CBC-HS256");
    jwe.SetProtectedHeader(jweProtHdr);

    String aesWrappingKey = "GawgguFyGrWKav7AX4VKUg";
    jwe.SetWrappingKey(0,aesWrappingKey,"base64url");

    // Encrypt and return the JWE in sbJwe:
    CkStringBuilder sbJwe = new CkStringBuilder();
    success = jwe.EncryptBd(jpgBytes,sbJwe);
    if (success != true) {
        Log.i(TAG, jwe.lastErrorText());
        return;
        }

    // Show the JWE:
    Log.i(TAG, sbJwe.getAsString());
    Log.i(TAG, "size of JWE: " + String.valueOf(sbJwe.get_Length()));

    // ---------------------------------------------------------
    // Decrypt to get the original JPG file..

    CkJwe jwe2 = new CkJwe();
    success = jwe2.LoadJweSb(sbJwe);
    if (success != true) {
        Log.i(TAG, jwe2.lastErrorText());
        return;
        }

    // Set the AES wrap key.
    jwe2.SetWrappingKey(0,aesWrappingKey,"base64url");

    // Decrypt.
    CkBinData jpgOriginal = new CkBinData();
    success = jwe2.DecryptBd(0,jpgOriginal);
    if (success != true) {
        Log.i(TAG, jwe2.lastErrorText());
        return;
        }

    Log.i(TAG, "Decrypted JPG size = " + String.valueOf(jpgOriginal.get_NumBytes()));

    // Save the decrypted JPG to a file.
    success = jpgOriginal.WriteFile("qa_output/jwe_decrypted_starfish.jpg");

    Log.i(TAG, "success = " + String.valueOf(success));

    // The output of this program, when tested, was:
    // Original JPG size = 6229
    // eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.9YFz_wteV ... 7Et3hKhpxnKEXw
    // size of JWE: 8473
    // Decrypted JPG size = 6229
    // success = True

  }

  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."
  }
}