code: private void initWithKey(byte[] key) throws SymmetricKeyException {
          if (key == null)
              throw new SymmetricKeyException("Key cannot be null");
          if (key.length != KEY_SIZE)
              throw new SymmetricKeyException("Key size is not " + KEY_SIZE + "bytes");
          keyData = key;
      }
docs: Initialize the object with a raw key of 32 bytes size.
  @param key 32 bytes raw key
  @throws SymmetricKeyException