Account verification: Only 1 account per person

Question

In my community, every user should only have one account.

So I need a solution to verify that the specific account is the only one the user owns

Answer 1

It's impossible to accomplish this with a program.

The closest you can do is to check the ip address. But it can change, and proxies exist.

Then you could get the computer MAC address, but a network card can be changed. And a computer too.

Then, there is one way to do this, but you need to see the people face to face. Hand them a piece of paper with a unique code. They can only subscribe if they have the code.