If you'd like to dig a little deeper on how perlmonks.org works check out chromatic's discussion over on everydevel.com. (hopefully this is the same chromatic here! :) )

Anatomy of an Everything Request

I know... FMTYRWTK

Another method, kinda building on what Fastolfe said, is how the phplib library for PHP works. It sets a unique SessionID in a cookie which is then tied to a record in a SQL database where the session variable are held. The ID is created relatively randomly and then encoded with a "secret password". The password is put into the phplib Session object definition. I'm pretty sure that the md5 algorithm is used in the encoding process. The weakness is keeping the file that contains the secret password safe from the whily crackerz.

So, I think, it's like this: md5( <random number> + <secret password>) = SessionID

fongsaiyuk