Delphi, Active Directory, Single Sign-on, login with PKI card

Hi, Need to give my Delphi application additional functionality. The user is login to Windows with PKI card, which registers him in Active Directory (with LDAP) and I need to recognize in my Delphi app the user logged in on maschine from Active Directory. The idea is that user just starts my app and do not need to enter login nor password. Need it to work with Delphi XE 4 and LDAP.