you can set up a data base and some php code to call from the data base and basicy you can turn a address in to the domain address with just a id number, its used to make long page address's short but it could be used to hide the address.
eg:
https://vborg.vbsupport.ru/hdhd/dhdh...howthread.php?
could get turn it to
http://www.vbulletin.org/yourphp.php=id1
im not up to speed with the full codeing but i know it can be done.