Embodiments of the invention include a mobile network entity, such as Access and Mobility Management Function AMF, providing registration management functions in a mobile network supporting network slicing, said mobile network entity configured to:—check if authentication and/or authorization involving a third party associated with a network slice is required for access to said network slice in addition to authentication and/or authorization for access to said mobile network, during registration,—initiate said authentication and/or authorization involving said third party upon checking that said authentication and/or authorization involving said third party is required.