问题
I would like to limit the possibility of creating more than one account in a web application by a single person. How to do this?
If you know how, you can directly answer this question. If you don't know or you don't understand the question, please read below where I try to give more information.
The problem can be solved by assigning a unique persistent ID to each person registering in the application. If the person wants to set up another account, it won't be possible because he/she will still have the same ID.
Now, how to assign an ID to a person?
One of the possibilities is to authenticate a user by a verified PayPal account. To verify his/her PayPal account, a person must do it by a bank transfer or a credit card. A person can only have one PayPal account for private purposes. So it is sufficient to use OAuth and receive the ID of a verified PayPal account. The only problem is, as you can read at https://developer.paypal.com/developer/applications/, that the developer of a "live" application must ask PayPal for permission to fetch verification status from PayPal via OAuth.
Important: Full name is approved by default. Sharing all other customer data requires approval through the app review process. Please send your app review request to help-loginappreview@paypal.com.
Without permission I cannot select "Connect with PayPal (formerly Log In with PayPal)" > "Account Information" > "Account verification status". And I don't know if PayPal will agree. Information about verification status is important because, if I am correct, in practice a person can register any number of unverified PayPal accounts.
Are there any other options?
Maybe ask a user to pay $0.01 using his/her credit card? How to identify a person based on the information I obtain after the payment? A person can have more than one credit card, so the number of a credit card is not enough. Also, first name and surname aren't enough since two people can have the same name. Maybe the combination of first name, surname and some address registered during applying for a credit card? Will I obtain such information after payment?
Using SMS to verify a person's phone number isn't a solution since a person can have more than one phone number. Linking to Facebook or Google account seems to be not an option since in practice a person can have several Facebook or Google accounts. The same with OpenID - one can have more than one OpenID, and the same with an email address.
I have read:
- Account verification: Only 1 account per person
- Possible to make a one account per person website?
- I want to create a website where one person have only one account. But how I will do it if a person uses VPN or proxy?
but I haven't found a proper answer. On the other hand, my idea to verify a user using PayPal verified account seems to be quite ok. The only question is if PayPal will agree to this.
来源：https://stackoverflow.com/questions/57360488/only-one-account-for-one-person-how-to-restrict