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Posted by The Natural Philosopher on 11/14/07 11:40
damezumari wrote:
> I have a simple voting page using php and mysql and wonder how I can
> prevent users from voting twice.
>
> Here are three ways:
>
> 1. IP locking or IP locking with a time limit
> The same IP address can not vote twice, or not vote twice within the
> time limit.
>
That locks out entire networks that enforce proxy servers...
> 2. Cookies, weak version.
> If the user has cookies turned on they can only vote once. The cookie
> may be stored on the server and last till the browser is closed, or on
> the client and last till the user deletes it.
> If the user has cookies turned off they can vote as many times as they
> like.
mm.
>
> 3. Cookies, strong version
> If the user has cookies turned on a cookie (session variable) is
> stored on the server and last till the browser is closed.
> If the user has cookies turned off they are told to turn it on for at
> least the present site.
>
> I exclude any options that uses usernames and/or passwords as that
> would be too cumbersome for most users.
>
> Disadvantages with each method:
>
> 1. Users behind a proxy have the same IP address. This means that if
> one has cast a vote, the others can't or have to wait a certain time
> to do so.
>
> 2. This allows repeated voting too easily.
>
> 3. People may decide not too vote as they do not want to take the time
> to turn cookies on for the present site, or are generally sceptical
> about cookies at all. They may vote again when they reopen the
> browser.
>
> Personally I like best method 3, but post my thoughts here to hear
> your ideas.
>
> Are there other ways than the 3 listed? Which one do you like the
> best? Why?
>
> Regards,
>
> Jan Nordgreen
>
Frankly it can't be done reliably. 3 is the bet of a a bunch, but I
would never use it in any situation where accuracy was needed.
How does one cater for the person who hits every browser in an internet
cafe? or the single machine in an entire classrooom that all the kids
want to vote, using.
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