Yubico Forum

Has anyone else noticed that when testing the webclients (so far for md the PHP and C ones) - that you can supply any user ID number - not just the one genned for your key.

For instance when testing the C client - I can run the supplied compiled C program with the following:

YubicoClient 125 (press Yubikey here) - and it will reply with a pass.
----------------------------
* OTP verified OK
* Last response: t=2008-06-15T20:14:22Z0438
status=OK
----------------------------

You can do this with any number - as long as the web api has genned it online.

Am I mistaken - or should it only work for my individual key?
(IE - I have to use 139 - because my key was genned with the "online API key generator" and it displayed 139)

thanks

The unchanging user ID number is only used as a convenient way to identify a Yubikey without having to know the private ID or the AES key. You could, for example, use it to look up the AES key in a database, and then decode the rest of the one-time-password. Then, using the database again, you could check the OTP's private ID with the one you stored in the database.

If someone were to spoof your public user ID, they still wouldn't know the correct private ID or AES key.

You are right that you can use any existing client id -- however, to verify the signature, you'll need the secret HMAC key that only the "real" client id holder would know.

/Simon