A method of performing authentication and authorization in Proximity based Service (ProSe) communication by a requesting device which sends a request of a communication and a receiving device which receives the request from the requesting device, the method including deriving session keys Kpc and Kpi from an unique key Kp at the requesting and receiving devices, using the session keys Kpc and Kpi for ProSe communication setup and direct communication between the requesting and receiving devices, starting the direct communication with the requesting and receiving devices. The key Kpc is confidentiality key and the key Kpi is integrity protection key.