I want to avoid user registration in my app, and to identity my user by purchased app. 
If someone purchase app on his iPhone, and with the same Apple ID download this app on other device, I want to use the same settings and content on this devices.

**Is posible to use identifiers like AppleID (without entering in input field by user)?**

I found similar [question](https://stackoverflow.com/questions/227590/unique-identifier-for-an-iphone-app) but UniqueIdentifier is unique only for physical device, not for user.