n for the user which consists of the user's IP address, the target <span th:text="${settings.shortcut}"></span> address <span class="math-term">A</span>, the timestamp <span class="math-term">T</span>, and a random challenge <span class="math-term">C</span>.
                            The server sends the challenge <span class="math-term">C</span> back to the user.
                        </li>
                        <li class="text-justify">The user starts to calculate responses <span class="math-term