public boolean registerUser(String username, String password, String email) throws SQLException, NoSuchAlgorithmException{
        ResultSet rs= ctrl.doQuery("SELECT * FROM utenti WHERE username='"+username.toLowerCase()+"'");
        if(rs.next()){
            rs.close();
            return false;
        }
        else{
            boolean result;
            MessageDigest md = MessageDigest.getInstance("MD5");
            md.update(password.getBytes());

            byte byteData[] = md.digest();

            StringBuffer sb = new StringBuffer();
            for (int i = 0; i < byteData.length; i++) {
             sb.append(Integer.toString((byteData[i] & 0xff) + 0x100, 16).substring(1));
            }

            password= sb.toString();
            result= ctrl.iumQuery("INSERT INTO utenti (username, password, email, privilege) VALUES ('"+username.toLowerCase()+"', '"+password+"', '"+email.toLowerCase()+"', 0)" );
            return result;
        }
    }