Recently I met a problem when use google in app billing. There is an android crack software named 'Freedom'. It crack google in app billing, when the user ask for a purchase, it will simulate a success payment notify, then my game app will add gems for user, but google backend doesn't receive any payment. The picture below is a screenshot of the crack app, it use a 'FreeCard-xxx', I don't know what it is.
https://i.stack.imgur.com/JZraJ.png
At first, I want to verify payment order on my game server, so I use Google Play Android Developer API (https://developers.google.com/android-publisher/index), but the Developer API need Authorization. The process of Authorization must let user use browser to create a 'code', paste and send code to my game server. This is impossible in my app.
Is there any good way to verify payment order info or any good idea to prevent my app from cracking by 'Freedom' ?
Any help will be appriciated, thanks:)
