how to encrypt and decrypt audio file android

Question

I am trying to encrypt and then decrypt audio file . Everything goes right but when I try to decrypt the encrypted audio , everytime I got this exception

javax.cryp

Answer 1

After days of research and hard work I found the solution ,may help and save somebody's else time . Here is my answer. I changed the above code logic like this

now what is happening , I am able to successfully encrypt the file and save it in the sdcard and then decrypt it to play . No body else can play the audio.

here we go : happy coding

public class Main2Activity extends AppCompatActivity {

    private String encryptedFileName = "encrypted_Audio.mp3";
    private static String algorithm = "AES";
    static SecretKey yourKey = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

        //saveFile("Hello From CoderzHeaven asaksjalksjals");
        try {
            saveFile(getAudioFile());
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        decodeFile();

    }

    public static SecretKey generateKey(char[] passphraseOrPin, byte[] salt) throws NoSuchAlgorithmException, InvalidKeySpecException {
        // Number of PBKDF2 hardening rounds to use. Larger values increase
        // computation time. You should select a value that causes computation
        // to take >100ms.
        final int iterations = 1000;

        // Generate a 256-bit key
        final int outputKeyLength = 256;

        SecretKeyFactory secretKeyFactory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
        KeySpec keySpec = new PBEKeySpec(passphraseOrPin, salt, iterations, outputKeyLength);
        SecretKey secretKey = secretKeyFactory.generateSecret(keySpec);
        return secretKey;
    }

    public static SecretKey generateKey() throws NoSuchAlgorithmException {
        // Generate a 256-bit key
        final int outputKeyLength = 256;
        SecureRandom secureRandom = new SecureRandom();
        // Do *not* seed secureRandom! Automatically seeded from system entropy.
        KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
        keyGenerator.init(outputKeyLength, secureRandom);
        yourKey = keyGenerator.generateKey();
        return yourKey;
    }

    public static byte[] encodeFile(SecretKey yourKey, byte[] fileData)
            throws Exception {
        byte[] encrypted = null;
        byte[] data = yourKey.getEncoded();
        SecretKeySpec skeySpec = new SecretKeySpec(data, 0, data.length, algorithm);
        Cipher cipher = Cipher.getInstance(algorithm);
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec, new IvParameterSpec(
                new byte[cipher.getBlockSize()]));
        encrypted = cipher.doFinal(fileData);
        return encrypted;
    }

    public static byte[] decodeFile(SecretKey yourKey, byte[] fileData)
            throws Exception {
        byte[] decrypted = null;
        Cipher cipher = Cipher.getInstance(algorithm);
        cipher.init(Cipher.DECRYPT_MODE, yourKey, new IvParameterSpec(new byte[cipher.getBlockSize()]));
        decrypted = cipher.doFinal(fileData);
        return decrypted;
    }

    void saveFile(byte[] stringToSave) {
        try {
            File file = new File(Environment.getExternalStorageDirectory() + File.separator, encryptedFileName);

            BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(file));
            yourKey = generateKey();
            byte[] filesBytes = encodeFile(yourKey, stringToSave);
            bos.write(filesBytes);
            bos.flush();
            bos.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    void decodeFile() {

        try {
            byte[] decodedData = decodeFile(yourKey, readFile());
           // String str = new String(decodedData);
            //System.out.println("DECODED FILE CONTENTS : " + str);
            playMp3(decodedData);

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public byte[] readFile() {
        byte[] contents = null;

        File file = new File(Environment.getExternalStorageDirectory()
                + File.separator, encryptedFileName);
        int size = (int) file.length();
        contents = new byte[size];
        try {
            BufferedInputStream buf = new BufferedInputStream(
                    new FileInputStream(file));
            try {
                buf.read(contents);
                buf.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        return contents;
    }

    public byte[] getAudioFile() throws FileNotFoundException
    {
        byte[] audio_data = null;
        byte[] inarry = null;
        AssetManager am = getAssets();
        try {
            InputStream is = am.open("Sleep Away.mp3"); // use recorded file instead of getting file from assets folder.
            int length = is.available();
            audio_data = new byte[length];
            int bytesRead;
            ByteArrayOutputStream output = new ByteArrayOutputStream();
            while ((bytesRead = is.read(audio_data)) != -1) {
                output.write(audio_data, 0, bytesRead);
            }
            inarry = output.toByteArray();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return inarry;

    }

    private void playMp3(byte[] mp3SoundByteArray) {

        try {
            // create temp file that will hold byte array
            File tempMp3 = File.createTempFile("kurchina", "mp3", getCacheDir());
            tempMp3.deleteOnExit();
            FileOutputStream fos = new FileOutputStream(tempMp3);
            fos.write(mp3SoundByteArray);
            fos.close();
            // Tried reusing instance of media player
            // but that resulted in system crashes...
            MediaPlayer mediaPlayer = new MediaPlayer();
            FileInputStream fis = new FileInputStream(tempMp3);
            mediaPlayer.setDataSource(fis.getFD());
            mediaPlayer.prepare();
            mediaPlayer.start();
        } catch (IOException ex) {
            ex.printStackTrace();

        }

    }
}