RijndaelEngine rijndaelEngine = new RijndaelEngine(256); // *1 *2 KeyParameter keyParam = new KeyParameter(rijndaelKeyBytes) rijndaelEngine.init(false, keyParam); //false == decrypt PaddedBufferedBlockCipher bbc = new PaddedBufferedBlockCipher(rijndaelEngine, new ZeroBytePadding()); // *3 byte[] decryptedBytes = new byte[decryptedLenght]; //from the storageOptions string int processed = bbc.processBytes(inputBytes, 0, inputBytes.length, decryptedBytes, 0); bbc.doFinal(decryptedBytes, processed);