I've got a few questions about device check, and would be grateful if anybody knows the answers:
- why is DC not reset when the device transfers between users?
The canonical example of why an app might use DC is if it offers a promotion and to stop user's from getting that promotion multiple times. However, using the same example scenario yes you've stopped the first user from getting multiple promotions but then if that device is transferred to another user you've stopped them from getting any promotions at all?
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how can you test things when the bits can't be reset? If once you've set the bits on a device then you can no longer ever use that device again to test the apps behavior in the situation when the bits are unset.
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does the app have complete freedom to set the timestamp to whatever it wants? For example, could the app set a bit with a timestamp of epoch?
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if the bits are shared between all apps from the same developer, then supposing that developer have more apps in the App Store then there are bits? If they have 5 apps offering a promotion and a device has previously had 4 apps installed, then the user wants to install a 5th app, but with all 4 bits now then the user will be able to abuse the promotion on the 5th app because the app has no way of recording if the promo has been used or not as the collective bits have been used up?