Section: 10.2.2.3 Key generation for Unauthenticated IMS Emergency Sessions 10.2.2.3.1 General
Content: An unauthenticated UE does not share a complete 5G NAS security context with the network as there has been no successful primary authentication run between the UE and the AMF. When the UE and the AMF does not share the security context the only possibility for an AMF that allows unauthenticated IMS Emergency Sessions is to run with the NULL integrity algorithm NIA0 and the NULL ciphering algorithm NEA0. When there has been no successful run of Primary authentication of the UE, the UE and the AMF independently generate the KAMF in an implementation defined way and populate the 5G NAS security context with this KAMF to be used when activating a 5G NAS security context. All key derivations proceed as if they were based on a KAMF generated from a successful Primary authentication run. Even if no confidentiality or integrity protection is provided by NIA0 and NEA0, the UE and the network treat the 5G security context with the independently generated KAMF as if it contained a normally generated KAMF.