Uniquely Identify iOS device over multiple users

Question

I have done a lot of research on this so please read the question before marking this as similar to some other question.

Our app needs to uniquely determine an iPhone such that even when user completely wipes a phone, when he runs our app we can be sure that it is the same device. The most important thing is we also need to determine devices over multiple Apple ID users so suggestions containing Keychain access and uniqueVendorID might not work as those change when another user starts using that phone. And as I have read using MAC addresses and old UDID for devices is not longer available as of iOS 6.0. I went through [UIDevice identifierForVendor] but this NSUUID changes when all the app by the same vendor has been uninstalled Reference.

I have looked through these resources:

UIDevice uniqueIdentifier Deprecated - What To Do Now?

and

What is a long-term method I can use to uniquely identify an iOS device?

I can not disclose the nature of work that my app performs due to non-disclosure, but to clarify what I require:

Multiple users might use our app on same phones, I need a way to know that the device user A used before and has reported to have handed over to user B is the same device on which our app was run. Is there any way to achieve this?

Answer 1

There's no way to achieve this.

If it's really the case that different users might use your app on the same device after a factory reset of the device, then what you want is not possible. Apple deprecated UIDevice uniqueIdentifier which would have been the way to do this.

Answer 2

as long as they dont restore/wipe the device identifierForVendor is ok