Section: 6.4.4.2 NAS confidentiality activation
Content: NAS confidentiality shall be activated using the NAS SMC procedure or after an inter-system handover from EPC. Once NAS confidentiality has been activated, NAS messages without confidentiality protection shall not be accepted by the UE or the AMF. Before NAS confidentiality has been activated, NAS messages without confidentiality protection shall only be accepted by the UE or the AMF in certain cases where it is not possible to apply confidentiality protection. NAS confidentiality shall stay activated until the 5G security context is deleted in either the UE or the AMF.