Generating a unique Device ID for iOS app

In the MACH Registrations API, you are required to submit a parameter value called 'DeviceUID' which is supposed to be unique for each user of an iOS app. 

For before iOS7, there is a fantastic and free library already available to solve this (released under an MIT license) 

https://github.com/gekitz/UIDevice-with-UniqueIdentifier-for-iOS-5

For iOS7, please use the identifierForVendor method as described in this link:

https://developer.apple.com/library/ios/documentation/uikit/reference/UIDevice\_Class/Reference/UIDevice.html