Is HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Cryptography\MachineGuid unique?

Question

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In the Windows registry is a key called MachineGUID that has a UUID which is created by Windows during installation and should in theory be unique to the machine. In practice this is not the case and I have often come across duplicates of this ID between machines.

I don't understand why it wouldn't be unique, I mean does Windows uses some weak algorithm to generate this GUID or something?

Answer 1

If a machine is restored from a backup or clone (such as in disaster-recovery, lab rollout, or fast VM deployment scenarios) then the MachineGuid value would be the same on multiple machines.

I note that the key value itself is read/write, so a post-setup or userland application could overwrite this too, even to a duplicate non-unique value.