I'll welcome all comments:

I manage a web portal written in classic asp.
A client wants to add a link to our portal using a Single Sign On (sso) via their secure portal.
They (the client) will be using SAML passing a UID and TIN.
I just do not know how to get started (I've spent hours researching sample/books forums with no luck).
Has anyone accomplished this? If so can you advise?

I've written SSO when going from our web portal to another client, but the other way around I'm totally lost.

Any help would be really appreciated.