I want to post a paid video course on my WordPress website. I would like to have user name and password authentication BUT would also like a way that the person who purchased the course can't just give their login credentials to someone else. Perhaps writing a cookie to their computer and reading that cookie to allow them to login. If they gave their user name and password to someone else, it wouldn't work for that person because there would be no cookie on their computer.
Perhaps there are better ways to do this other than using a cookie?