How are traded credits tracked, if login is not necessary?

It was mentioned that I don't have to be logged in for my traded (space * uptime) credit to be applied to my account. How is this achieved? Is it based on a unique hash for each running client? Is it tracked by IP address? (cause I have a dynamic IP, ya know) I want to understand the limits of how this works.

I don't want to login if there's a sure way I'll be attributed credit (mainly because the password thing seems very insecure to automate). Also, if my IP changes, should the -nogui "daemon" be restarted?

Thanks.