Question

I`m managing an online trading game system.
I require the following fields upon registration:

• Email
• Username
• Password
• Sex
• Phone Number
• Name and Surname

And the users IP upon registration.

The point is that I imposed to written Terms and Conditions on the site:
One user can have 2 usernames under the same IP, everything which finds itself outside this condition will be disqualified.
So two users having thus 4 usernames registered under the same IP are prone to fraud.

My problem is:
How do I uniquely identify each user.

I cannot use the IP, because there can be multiple users behind a router or worse use Mobile GPRS, etc.

I cannot use a social identification number, cause they might gather all of their relatives and use their social number.

Emails, everyone can set an email pretty easy.

I`m running out of ideas.

Later Edit: I could enforce a security key, generate one for each user subscribed, with that key, the user can later add another user, on a different IP.

I know It will probably not be as secure, but it will certainly make it harder

Answer 1

You could use their phone number, and require them to receive a registration text. They could still use a friend’s phone, but it would be a lot less prone to abuse.

Is there a cash prize involved? If so, there’s probably nothing you can do to completely prevent abuse.