Case

$ cd nginx-0.8.53
$ ./configure --add-module=../ngx_http_secure_download/

        location /somefolder {
            secure_download on;
            secure_download_secret IAmSalt$remote_addr;
            secure_download_path_mode file;
 
            if ($secure_download = "-1") {
                rewrite /expired.html break;
            }
            if ($secure_download = "-2") {
                rewrite /bad_hash.html break;
            }
            if ($secure_download = "-3") {
                return 500;
            }
 
            rewrite ^(.*)/[0-9a-zA-Z]*/[0-9a-zA-Z]*$ $1 break; // crop all the /hash/time stuff off the url
        }

function secure_url($url)
{
  $ts = time() + 3600;
  $ts_in_hex = dechex($ts);
  $secret = 'IAmSalt' . $_SERVER['REMOTE_ADDR'];
  $hash = md5($url . '/' . $secret . '/' . $ts_in_hex);
  return  $url . '/' . $hash . '/' . $ts_in_hex;
}