Editing My 3GPP 33.501 notes (section)

=== 6.7.1 Procedures for NAS algorithm selection ===

==== 6.7.1.1 Initial NAS security context establishment ====
Each AMF shall be configured via network management with lists of algorithms which are allowed for usage. There shall be one list for NAS integrity algorithms, and one for NAS ciphering algorithms. These lists shall be ordered according to a priority decided by the operator.

To establish the NAS security context, the AMF shall choose one NAS ciphering algorithm and one NAS integrity protection algorithm. The AMF shall then initiate a NAS security mode command procedure, and include the chosen algorithm and UE security capabilities (to detect modification of the UE security capabilities by an attacker) in the message to the UE (see sub-clause 6.7.2 of the present document). The AMF shall select the NAS algorithm which have the highest priority according to the ordered lists.

==== 6.7.1.2 AMF change ====
If the change of the AMF at N2-Handover or mobility registration update results in the change of algorithm to be used for establishing NAS security, the target AMF shall indicate the selected algorithm to the UE as defined in Clause 6.9.2.3.3 for N2-Handover (i.e., using NAS Container) and Clause 6.9.3 for mobility registration update (i.e., using NAS SMC). The AMF shall select the NAS algorithm which has the highest priority according to the ordered lists (see sub-clause 6.7.1.1 of the present document).