Secure voting website

Question

I am willing to implement website where will be top 10 best members' pictures or something like that. Before voting for pictures or uploading pictures people will have to register first. But how could I protect my website from multiple accounts? Store IPs to database? But will it help me while there thousands proxies out there? What should I do? Thank you.

edit: maybe I could make accounts paid, for examples 0.99$ for month via paypal and somehow do no let people register twice with the same paypal and IP? Is it possible?

Answer 1

Use a confirmation code that is sent to mobile no upon registration. and confirm it. like google.

Answer 2

You can't stop it, but you can make it difficult and do things to detect it like you said with the IP's.

Answer 3

You can get a lot of data from user, not only IP but also browser version, sended headers in request, even resolution etc. with javascript. Rosolve IP to region etc. But it's not simple to write a system that would search all of that data for similarities.

You can also set cookies or even do a little swf object with cashed some information on user local hdd.

Answer 4

You can send mail confirmation... and don't allow multiple users from the same mail!

This is fast and easy to implement :)