No checksum on Apple iPhone UDIDs

Just found out the hard way that there is no checksum on the UDID of Apple devices (iPhone, iPad, iPod Touch etc.). The UDID is a unique identification for the device, and is used during development to allow pre-release versions of apps to be tested on real hardware before submitting to the App Store. This allows developers to test the app, but allows Apple to ensure the app isn’t generally released without going through their App Store.

For such a long number (a 40 digit hexadecimal string), I would have thought that there would be some form of checksum in there – technology that has been around since I don’t know when and is prevalent in all fields of computing where having correct data is important. Even credit card numbers have a form of checksum built-in to guard against error.

However, alas it seems there is no checksum in the number as I’ve found out that a UDID we were provided had one digit wrong. Wouldn’t normally be a massive issue, but due to circumstance it will be a pain to rebuild and get the app we want to put on the device on it. So if you are getting a UDID from someone in the future, recommend that you ask for a screenshot to be sure.