I am developing an application from which users browse and buy books. The client can be Android ,iOS, Mac. The server is ASP.net Web APIs.
I know there are many payment services available. One of these is Authorize.net, which I think I will use. When a user pays for a book, he/she will get a unique link to download data from the server. I want to prevent other users who has unlawfully retrieved that link from downloading data. Additionally, I want to keep users' payment information secure.
I have no experience in security. So, please give some advice on how to implement this. Thanks.