An authentication method and system for mutual authentication between a first entity and a third entity via a second entity, based on an authentication protocol used by the first entity and the third entity. The second entity forwards mutual authentication messages between the first entity and the third entity. An apparatus is configured to perform an authentication method for a mutual authentication between a first entity and a third entity via a second entity, based on an authentication protocol used by the first entity and the third entity, the second entity forwards mutual authentication messages between the first entity and the third entity.