code: protected static final byte[] decrypt(byte[] msg, byte[] key, String cipher) throws Exception {
          SecretKey sKey = constructSecretKey(key, cipher);
          Cipher ci = createCipher(Cipher.DECRYPT_MODE, key, cipher, sKey);
          return ci.doFinal(msg);
      }
docs: Decrypt the specified msg.
  
  @param msg The byte representation of the data
  @param key The key used to decrypt the data
  @param cipher The cipher algorithm
  @return The decrypted data (plaintext)