1URI.MungeSecretKey
2TYPE: string/null
3VERSION: 3.1.1
4DEFAULT: NULL
5--DESCRIPTION--
6<p>
7    This directive enables secure checksum generation along with %URI.Munge.
8    It should be set to a secure key that is not shared with anyone else.
9    The checksum can be placed in the URI using %t. Use of this checksum
10    affords an additional level of protection by allowing a redirector
11    to check if a URI has passed through HTML Purifier with this line:
12</p>
13
14<pre>$checksum === hash_hmac("sha256", $url, $secret_key)</pre>
15
16<p>
17    If the output is TRUE, the redirector script should accept the URI.
18</p>
19
20<p>
21    Please note that it would still be possible for an attacker to procure
22    secure hashes en-mass by abusing your website's Preview feature or the
23    like, but this service affords an additional level of protection
24    that should be combined with website blacklisting.
25</p>
26
27<p>
28    Remember this has no effect if %URI.Munge is not on.
29</p>
30--# vim: et sw=4 sts=4
31