The standard Apache module ``mod_rewrite'' is used for translating incoming SURLs into URLs. If installed this module can be configured to translate arbitrary requested URLs into another form. Rules determine which requested URLs the module modifies.
In our case, the module starts a perl script that communicates with the scrambler over a socket. Every time a requested URL has the form ``/secure/...'' this script sends the requested URL to the scrambler and gives the result back to the rewrite module. The rewrite module in turn makes the Web server process the modified URL instead of the requested one.