A method for communicating by a terminal, includes transmitting, to an MME, an attach request message including a public safety indication and/or a group communication indication; receiving, from the MME, an attach accept message including at least one type of information from among a ProSe identifier, a ProSe group identifier, and a ProSe group for performing a ProSe, ProSe-related functions of the terminal, and a proximity-related security key (ProSe key) The method further includes transmitting a ProSe registration request to a ProSe function server and receiving, from the ProSe function server, a ProSe registration response message pending authentication of the terminal.