Question: What happens when the target AMF decides to use NAS algorithms different from the ones used by the source AMF during mobility?
Option 1: The target AMF continues using the same NAS keys as the source AMF.
Option 2: The target AMF derives new NAS keys and provides needed parameters to the UE for N2-Handover or mobility registration update.
Option 3: The target AMF uses the existing KAMF to re-derive the NAS keys without any changes.
Option 4: The target AMF ignores the NAS algorithm change and continues with the handover process.
Explanation: When the target AMF decides to use different NAS algorithms, it needs to derive new NAS keys. To ensure secure communication, the target AMF must provide the necessary parameters to the UE for N2-Handover or mobility registration update, as defined in Clauses 6.9.2.3.3 and 6.9.3, respectively. This ensures that the UE is aware of the changes and can adapt accordingly.