Tool to help generate
In the most common case (no exclusion rules, pair each guest with another at random), enter the name of your guests one line at a time. Once done, press "generate" and you're all set: send the generated links to your guests (by mail, chat, whatever floats your boat) and their pairing will be revealed to them (and only them) once they open the link.
Where does this tool come from?
I wanted to make a Secret Santa over Facebook without having to reveal to anyone my guests email addresses (so nothing that would require a backend). I also wanted not to know who was paired with me, so I had to find a way to somehow obfuscate the information. And being a developer, well, my first thought was "Let's AES it, for fun and profits!". Classic.