IAG SP2 allows end users to authenticate to the IAG portal and to application servers published through the portal by using form-based authentication with the following credentials: user principal name (UPN) and a password. Because the UPN of an end user is unique in a domain forest, the end user can authenticate to any application server within the forest without providing the domain as a credential.
When an end user authenticates to the IAG portal by using a client certificate (for example, a smart card) and then attempts to open an application that requires authentication, the UPN of that end user will be automatically displayed in the User name box, eliminating the need to manually type the user name.