title: Generate ip and time limited download link
body: <p>there is a direct link for download a file. users can download that link after payout, like this:</p>
  
  <pre><code>http://example.com/download/webapp.rar
  </code></pre>
  
  <p>But I need generate ip and time limited download link to prevent leech the file with others. I want to do this without use any databases. something like this :</p>
  
  <pre><code>http://example.com/download.php?a5fds588fgdf
  </code></pre>
  
  <p>or</p>
  
  <pre><code>http://example.com/download/a5fds588fgdf
  </code></pre>
  
  <p>is there any tips?</p>