Should I generate a lot of random serial keys and pick one for each registration or generate 1 for each user?

I’m talking about Online activation. My current workflow is:

User pays via paypal (without registration)
Paypal performs a request to my API.
My API returns a serial key to the user.
Then the user is able to register using this serial k… Continue reading Should I generate a lot of random serial keys and pick one for each registration or generate 1 for each user?