My head hurts

I've been thinking about a formula for my current project all night. Basically it's a simple way of organizing websites internal links. Many of you know that when you create websites you might have many vars to have proper usability. Now, my idea is to make a simple unpredictable formula similar to tinyurl. The idea is that a website url ending file.php?action=asd&id=1&user=username will be ending like file.php?ihgt54i

The idea is not to use any tables, so this method could be used for many things. If anyone has a solution, mail me, please!