public class EncryptionUtils {

  private MessageDigest dg = null;
  private String username, password;
  private byte[] key = null;

  public EncryptionUtils(String username, String password) {
    this.username = username;
    this.password = password;
  }

  public String encode(String message) {
    return byteArrayToString(getEncode(getKey(), message));
  }

  public String dencode(String message) {
    try {
      return new String(aes256Dec(getKey(), getEncode(getKey(), message)));
    } catch (Exception e) {
      e.printStackTrace();
    }
    return "";
  }

  private byte[] getKey() {

    if (key != null) {
      return key;
    }

    try {
      return hash(arrayMerge(username.getBytes(), hash(password.getBytes())));
    } catch (Exception e) {
      e.printStackTrace();
    }
    return new byte[]{0};
  }

  private byte[] getEncode(byte[] key, String message) {
    try {
      return aes256Enc(key, message.getBytes());
    } catch (Exception e) {
      e.printStackTrace();
    }
    return new byte[]{0};
  }

  private String byteArrayToString(byte[] bArr) {
    return DatatypeConverter.printHexBinary(bArr);
  }

  public byte[] stringToByteArray(String str) {
    return DatatypeConverter.parseHexBinary(str);
  }

  private byte[] arrayMerge(byte[] arr1, byte[] arr2) {
    byte[] res = new byte[arr1.length + arr2.length];
    System.arraycopy(arr1, 0, res, 0, arr1.length);
    System.arraycopy(arr2, 0, res, arr1.length, arr2.length);
    return res;
  }

  private byte[] hash(byte[] in) throws Exception {
    if (dg == null)
      dg = MessageDigest.getInstance("SHA-256");
    return dg.digest(in);
  }

  private byte[] aes256Enc(byte[] key, byte[] in) throws Exception {
    Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
    SecretKeySpec secretKey = new SecretKeySpec(key, "AES");
    cipher.init(Cipher.ENCRYPT_MODE, secretKey);
    return cipher.doFinal(in);
  }

  private byte[] aes256Dec(byte[] key, byte[] in) throws Exception {
    Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
    SecretKeySpec secretKey = new SecretKeySpec(key, "AES");
    cipher.init(Cipher.DECRYPT_MODE, secretKey);
    return cipher.doFinal(in);
  }
}