Own Online Subsystem / Google Login

Hey there,

i have a question and hoping some of you knows the answer or can give a hint in the right direction or has an advice for me.

I am working on an android app which uses the Google Subsystem for Highscores and IAPs, the problem i have is for the IAPs i have to manage myself, like coins or diamonds and such stuff i can buy more than on time.

Google does not manage sees values how much diamonds i have and the unreal savegame is to easy to manipulate to save these values there. So i came off with the idea to build up a small Rest API to handle this.

And the problem i am facing now is, how to make the login on the rest api for the user, is it possible to run a google authenticate and it will login via the same google account, which is used in app. The UE is only giving me the unique device id which is changing after a full device reset so it would be stupid to use this one. The next thing is i could create a complete account management into the app from register to login, but that seems a bit to much for a mobile game.

How do other mobile games handle this, are you guys saving the value into the unsecure savegame or have a class which encrypts the savegame?

Thanks for help, hints and advices.

Kind regards,
pyr0t0n