Windows System GUIDs (not unique) Why? How?

NickRobinson · 02 Dec 2011

So being an ASS I ass-umed that the system ID that you get when you ask Windows for a system ID is unique and I built a licensing scheme around it. I was wrong.

My system Id is not even close to being unique. Try googling this

{846ee340-7039-11de-9d20-806e6f6e6963}

and you can find it everywhere, usually referred to as a GUID.

What are the chances of that? They should be nil.

Anyone have any clue what is going on with this? Why are windows GUIDs not even close to being unique?

I have searched for an explanation but everyone seems blissfully unaware that they are not the only users of {846ee340-7039-11de-9d20-806e6f6e6963}

Please put me out of my (seemingly unbounded) ignorance.

Cheers,

Nick

EDIT: Check this out

http://msdn.microsoft.com/en-us/libr...=vs.85%29.aspx

"Globally Unique Identifier" it claims - not even close!

logicearth · 03 Dec 2011

Where are you getting this "System ID" GUID is only unique if you generate your own. Otherwise, a lot of systems will have the same GUID for various things like COM objects.

Also on Windows 7, Hardware profiles do not even exist any more. So the above function from MSDN is not going to return anything unique.

NickRobinson · 03 Dec 2011

I'm generating it in the method described in the MSDN article that I linked to. The article was updated quite recently and says it applies to Windows 2000 and above. there is no mention that it is obsolete.

The fact that the
GetCurrentHwProfile

call returns successfully would appear to indicate that this is implemented fully on Windows 7.

Still, thanks for the heads-up. I was already heading in the direction that I might have to do it all myself. I just hope they don't kind-of-but-not-really withdraw more functionality without really saying so in the documentation.

The poor documentation is why I generally try to stay as far away as possible from MS development.

Nick

NickRobinson · 03 Dec 2011

Sorry, the idea of the "same GUID" really doesn't make any sense. A unique identifier should be unique. Otherwise it is not a unique identifier.

logicearth · 03 Dec 2011

The function in question still works, however the act of making multiple hardware profiles is not available after Windows Vista, thus the same GUID for the default profile. The GUID that is returned is only an identifier for the current hardware profile not the hardware itself. Nor is it a "System ID" thus uniqueness was not fundamental for its purpose.

For the record, GUID is unique when it is not hardcoded to be the same.