Currently a user makes a purchase and then a license is generated and sent to that user, but the license isn't tied to a physical computer so there is nothing to prevent the user sharing the license with someone.

I heard people talk about creating a license tied to the mac address of the computer, so the license only works on that computer. Now I know how to get the mac address in code but I dont understand how I can do this step when they first make the purchase on the web, so please what is the basic algorithm for node locked licenses ?