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In our Windows desktop .Net application, we have a licensing system where we bill for every mchine where our system is installed.

So far we've been using szHwProfileGuid from GetCurrentHwProfile to determine what we called "installation id". We confronted it with a license key from registry and when it matched we've allowed a user to log in.

It worked fine until Windows 10 came out, which changes szHwProfileGuid every other update. This causes all of the license keys to become invalid.

Yes, I realize this mechanism is not bulletproof, but in our case it's good enough. I'm wondering though what would be the fastest way for us to substitute szHwProfileGuid with something less volatile.

Requirements

  • The value should be globally unique (number, guid or string) or at least it should be "close to unique".
  • The value should be accessible form the system without the need of storing it
  • The value should never change for a certain PC (a change when reinstalling Windows or changing hardware is acceptable, a change when Windows updates is unacceptable)
  • Spoofing the number is not a concern

Using mac address crossed my mind, but maybe you guys have better ideas?

Andrzej Gis
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  • Generate a GUID on installation and use that? – DavidG Dec 05 '17 at 17:52
  • @DavidG That would require them to store it. – juharr Dec 05 '17 at 18:00
  • @juharr Yes, and that's a problem why? – DavidG Dec 05 '17 at 18:02
  • Take a look at [this answer](https://stackoverflow.com/a/3443149/2592875). – TnTinMn Dec 05 '17 at 18:09
  • @DavidG You'd have to ask the OP since that's their second requirement. – juharr Dec 05 '17 at 18:42
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    You should use a hash of several things unlikely to change. The CPUId, BaseBoard ID and perhaps even the Windows serial (or windows key). You may also want to include something to identify the software and/or version so just that software validates rather than everything and anything. *Then* there is such a thing as deterministic GUIDs - using these your hash could look like a GUID rather than a hash result – Ňɏssa Pøngjǣrdenlarp Dec 05 '17 at 19:31

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