Username and password

Is there any way to ask from the client, for a username in combination with the password? The problem is that when using the Client ID that is a combination of the computer name and the logged user, it is possible that two users may have named their account with the same name. Am trying to write an authorization script for managing users and their permissions on accessing specific devices , and the Client ID is not very useful to me, because i would like for example a certain user to be able to use his account across different pc's, where the ClientID will be different.
If you could add this feature it would be perfect. I think the only addition would be in passing an extra parameter of the submitted username, along with the hashed password.

Thanks.