Save data between different package/apps

Question

I have both a free and a paid app. If the user first tries free version and acquire for example 10 gold and then upgrade to paid version I want him to keep those 10 gold and not do a fresh start.

So is there way to share and access data between apps? And I don't want to save it to root of SD card because user can easily modify it that way.

Answer 1

I think some developers circumvent this by using their paid app just to check the payment (if it's installed, you've paid for it) and keep everything (code wise) in the free version. You could as well just encrypt/decrypt the data written to the SD card. This would as well make it easier for the user to backup/restore those saves (and nothing would be lost in case the app is reinstalled or something like that).