Security context handling in 5g during connected mode

The present disclosure relates to methods and apparatus for flexible management of security context during AMF changes. One aspect of the disclosure is a mechanism to achieve backward security during idle mode AMF changes. Instead of passing the current NAS key to the destination AMF, the source AMF derives a new NAS key, provides the new NAS key to the destination AMF, along with a rekey indication indicating that the NAS key has changed. The target AMF sends the rekey indication to the UE. (Automatic translation with Google Translate, without legal value)