unique identifiers

My company is implementing Cisco Clean Access http://www.cisco.com/en/US/products/ps6128/index.html. the server needs either unique registry keys, or files. i can determine the registry key that specifies an installed product, but is there a consistent key or file that states definitions are up to date?

Can you post something more about what exactly you are looking for?
What registry keys do you mean in particular?

I don’t think you can find out if the definitions are up to date - if, for example, the program cannot connect to the updating servers (let’s say being restricted by a firewall), it cannot say that even itself.

I know i can use HKLM\SOFTWARE\ALWIL Software\Avast\4.0 as a watermark saying that avast is installed, but is there a subkey or file within avast that declares up to date definitions? i’m not sure if i can use part-vps-???.vpu as the file fingerprint, since the filename would be constantly changing.