code: public static String decrypt(String encrypted, String strkey)
      throws GeneralSecurityException {
          SecretKey key;
          if (strkey != null) {
              if (strkey.length() > 56)
                  strkey = strkey.substring(0, 55);
              key = new SecretKeySpec(strkey.getBytes(), algorithm);
          }
          else {
              if (defaultKey==null) defaultKey =
                  new SecretKeySpec(defaultKeyString.getBytes(), algorithm);
              key = defaultKey;
          }
          Cipher cipher = Cipher.getInstance(algorithm);
          cipher.init(Cipher.DECRYPT_MODE, key);
          byte[] encryptionBytes = decodeAlpha(encrypted);
          byte[] recoveredBytes = cipher.doFinal(encryptionBytes);
          String recovered = new String(recoveredBytes);
          return recovered;
      }
docs: Decrypt a string
  @param encrypted encrypted string to be decrypted
  @param strkey a default key will be used when passing null in
  @return decrypted original data