code: private static Key buildKey(final String userid, final String password) {
  		return new SecretKeySpec(Arrays.copyOf(
  				new SHA3.Digest512().digest((userid + ".uuid" + password).getBytes(StandardCharsets.UTF_8)), KEY_SIZE_IN_BYTES),
  				ALGORITHM);
  	}
docs: Builds the key.
  
  @param userid
  the userid
  @param password
  the password
  @return the key