Some part of the network must provide the information that is used to authenticate the user. This can be a special server (sometimes referred to as an authentication server or key distribution server) and contains a database that is used to hold public, private or secret keys of users, clients and servers. Users, clients and servers must trust that the information they receive from this database is correct. Although the actual authentication verification rests with the server that has the requested service, it must trust that the ticket/certificate or other authentication information presented to it came from the authentication server.