iOS convert CFUUID to MAC Address

Question

I know CFUUID is generated from MAC address and a few other stuff. So is there anyways to get the MAC address back from CFUUID?

We have a few bluetooth devices and all the user knows is the last 3 parts of the MAC address which is written on the device. So we wanna give the user and option to select the right device. On the iOS side, looks like all we have the the CFUUID. So is there's a way to convert the UUID back to mac address?

Or even better would be if there's a way to get a peripheral's MAC address directly instead of UUID, but doesn't seem like that's possible

Thanks

Answer 1

Well, as you might have learnt from the comments to your question, the answer is clearly: NO. It is not possible (practically) to get the seeds that generated a particular UUID. Provided that in fact the algorithm that generated your UUID did used the MAC Address of your device to generate it, and I guess you cannot guarantee that it is the case for the UUID generator you use, unless you have access to the UUID Generator code or algorithm (UUID Version 1 probably?) and it is not a opaque operation to you (Immediately defeating the very purpose of the uuid generation algorithm).

While you clearly are onto something when you say that the generation of a UUID might use the MAC address of the device, other components like timestamps, hashing, UDID (iOS Devices) and so on. The fact is that the MAC Address, could be just one of many factors used to generate the UUID so if you were to spend a lot of computing power into trying to deconstruct it out of a big sample of UUIDs generated by the same system under the same conditions; We will probably be talking about a quantum computer wasting computing power trying to explore as many combinations as particles in the observable universe so you get a MAC address that you may as well get as a characteristic from a Bluetooth peripheral if you like, and incidentally defeating the purpose of having a UUID in the first place, once more.

On the other hand, further to what somebody commented on your question: the reason you find UUIDs so boring, building on top of the previous paragraph idea, is so you can avoid collisions: Generating duplicates not just coming from the ones generated by your computer but from all the other ones generated by every device out there every moment of the day (to authenticate requests, create string index keys in a database, or identifying services and characteristics) so your cool service or characteristic named:

AAAAAAAA-BBBB-CCCC-DDDD-EEEEFFFF6666 

does not get confused with another cool foo service or characteristic with the same UUID.

In general, for more information check wikipedia or just the Core Bluetooth Programming Guide, form the developer portal. It is still under NDA so you have to be a registered iOS Developer with active developer program credentials to read it.

Answer 2

I was looking for a way to deploy platform-independent, static configurations of BLE devices. I was getting discouraged (Apple's UUIDs are +/- meaningless, and the MAC/BDADDR which can be obtained on most/all other platforms is not accessible from CoreBluetooth). Fortunately, I noticed that the "Device Information Service" profile (0x180A) contains a "System ID" attribute (0x2A23) which encodes the device's unique MAC/BDADDR address. I don't know if it is mandatory for a BLE device to expose this service, however.