The present invention provides a method performed by user equipment, a method performed by a base station, user equipment, and a base station. The method performed by user equipment includes: transmitting to a base station a Radio Resource Control (RRC) connection resume request; receiving an RRC response message transmitted by the base station and used as a response to the RRC connection resume request; in the case where the UE has transmitted the RRC connection resume request on the basis of Early Data Transmission (EDT), performing first security processing on the RRC response message; and in the case where the UE has not transmitted the RRC connection resume request on the basis of the EDT, performing second security processing on the RRC response message.