Federated authentication service

A federated authentication service technology ( 10 ) for authenticating a subject ( 20 ) residing in a subject domain ( 12 ) on a network to a server application ( 38 ) residing in a server domain ( 18 ), wherein an authentication mechanism ( 32 ) residing in an authentication domain ( 16 ) affects the service provided by the server application ( 38 ). A client ( 22 ), which may be integrated non-human instances of the subject ( 20 ), authenticates the subject ( 20 ) and a protocol proxy ( 34 ) mediates with the authentication mechanism ( 32 ) to obtain a name assertion which the client can use to access the server application ( 38 ). When multiple authentication mechanisms ( 32 ) are available, an optional agent ( 24 ), mechanism resolution process ( 26 ) and mechanism repository ( 28 ), all residing in an agent domain ( 14 ), may be used to resolve to one suitable authentication mechanism ( 32 ).