private String validatePassword(
     final Map<String, String> propertiesSentToClient,
     final Map<String, String> propertiesReadFromClient,
     final String clientName) {
   final DBUserController userController = new DBUserController();
   if (!userController.login(clientName, propertiesReadFromClient.get(HASHED_PASSWORD_KEY))) {
     if (userController.doesUserExist(clientName)) {
       return "Incorrect password";
     } else {
       return "Username does not exist";
     }
   } else {
     return null;
   }
 }