- ARE MAC ADDRESSES UNIQUE TO EACH NIC SERIAL NUMBER
- ARE MAC ADDRESSES UNIQUE TO EACH NIC BLUETOOTH
- ARE MAC ADDRESSES UNIQUE TO EACH NIC MAC
- ARE MAC ADDRESSES UNIQUE TO EACH NIC WINDOWS
The hardware profile of the device changes, such as when the user Unless the underlying hardware has changed, two calls from the sameĪpp will result in identical ASHWIDs. Order to protect user privacy, the ASHWID varies from app to app. The ASHWID provides a strong binding between the app/package and theĭevice by representing several individual hardware characteristics.
ARE MAC ADDRESSES UNIQUE TO EACH NIC SERIAL NUMBER
The serial number of the boot device ::GetVolumeInformationW(::SHGetFolderPathW(~),~) will be fairly unique but only 32 bits. If you have access, MachineGuid is in HKLM\SOFTWARE\Microsoft\Cryptography, which MS guarantees to be unique.
ARE MAC ADDRESSES UNIQUE TO EACH NIC WINDOWS
You also need to consider what you want to do if the user clones an OS install, or replaces the HD after a drive failure.īack in the Windows Desktop world, I used the MachineGuid registry key and the serial number of the boot device, but I'm fighting to get access to that info in a Windows Store app. And of course the user's login name/ID should be unique to that user, if you want something else to include in a hash. You might randomly generate a large number (64+ bits) and store that (eg in the registry). The best use of the ASHWID is for verifying that a user has only installed your app to a limited number of devices, and you do that by parsing the ASHWID and selectively comparing it to previously-seen ASHWIDs from that user.Īs for a unique hardware identifier, I suggest an MD5 digest of a string containing multiple components, of which some components of the ASHWID can play a part.
ARE MAC ADDRESSES UNIQUE TO EACH NIC BLUETOOTH
At work, I've seen dozens of daily collisions where one monthly is our tolerance.įurther, the ASHWID might frequently change for the same device - since Windows 8 will often run on laptops that might add a docking station, USB thumb-drive, or a plug-in Bluetooth adapter. No, the ASHWID is not guaranteed to uniquely identify a device. Am I right in being ultra-sceptical of this identifier, or am I missing something really significant? So this really doesn't seem very unique at all. (go to and plug in "6563" and "4294967296" for the actual calculation). Once you've allocated just 6,000 of them, it's roughly 50/50 that you've got two the same.
ARE MAC ADDRESSES UNIQUE TO EACH NIC MAC
With one MAC address and one hard disk with a two-byte identifier each, you have about 4 billion permutations. Seems like the same sort of problem as the Birthday Paradox, so I found a calculator for that and plugged in the numbers :) So, I guess the crux of my question really is how many devices have to be produced with the same CPU type and memory configuration before you're likely hit a duplicate. The MACs and drive serials would likely be adjacent. If the bytes used are anything other than the least significant digits (the rightmost, as a human reads them) are taken, then two identical laptops adjacent on the production line would probably have the same ASHWIDs. But just two bytes for those values really doesn't seem like enough. The format includes two bytes per hardware component, of which the most uniquely identifiable are MAC address and hard disk serial number. I'm struggling to see how this can possibly be guaranteed unique. We want to use a unique device identifier in a Windows 8 Metro app and the recommendation is an ASHWID, documented here:
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