Section: 6.9.2.2 Key derivations for context modification procedure
Content: As outlined in clause 6.9.2.1, whenever a fresh KgNB is calculated from the KAMF, the AMF shall transfer the KgNB to the serving ng-eNB/gNB in a message modifying the security context in the ng-eNB/gNB. The AMF and the UE shall compute the fresh KgNB as defined in Annex A.9 according to the rules in clause 6.9.6.4. An NCC value 0 is associated with the fresh KgNB. From the fresh KgNB, the ng-eNB/gNB and the UE shall compute the KNG-RAN* as described in Annex A.11 and A.12 and then use the computed KNG-RAN* as the KgNB/KeNB as described in clause 6.9.4.4. NOTE 1: Unlike EPS, in 5GS the NAS and the AS security contexts are synchronized as a part of handover procedure, if a handover is occurring. See sub-clauses under the clause 6.9.2.3 (key derivations during handover) of the present document.