Best way to prevent multiple votes on a survey?

[SAMWeb]

Hi Everyone,

I need to implement a survey on my site that serves as an rsvp to an event (open invitation). The requirements are:

~ Allow user to indicate attendance at the national event, their local event, or both
~ Only allow one vote per visitor
~ Determine visitor's state

I can create the survey, but what's the best way to prevent multiple submissions from the same user? I could do it by IP, but what about users going through a proxy? I could do it via setting a cookie, but then the issue comes up when they clear their temp files. I could do it based on email, but that adds a field that the user needs to enter, and some might not want to enter that info, and some could vote multiple times using different email addresses. I would prefer just a simple, "Are you going? Click here" interface.

I also need to determine what state the person is in. I could have them provide the info viaa dropdown, but is there a more elegant way?

Thanks!

[Aristotle]

I think using cookies is the safest way to go. You could also do by IP, but limit the voting to maybe 1 vote per IP per 15 minutes?

Aristotle

DiscountASP.NET
www.DiscountASP.NET (http://www.DiscountASP.NET)

[SAMWeb]

Thanks, Aristotle.


The only problem I have with IP is that if a user is in a corporate setting, they are likely going through a proxy server, so all employees would have the same IP facing the internet -- which would only allow one person from that corp to vote in my survey.


With cookies, users could not accept them or delete them.


I don't suppose there's any way to capture the machine name in a non-intranet setting, is there?


Also, any way to determine their state without having them enter it?


Thanks!