Security context in a wireless communication system

1. A method performed by core network equipment configured for use in a core network of a wireless communication system, wherein the wireless communication system comprises the core network and a radio access network, the method comprising:

switching to using a new non-access stratum, NAS, security context between a user equipment and the core network equipment; and

during or in association with a handover procedure for handover of the user equipment, signaling from the core network equipment that the new NAS security context between the user equipment and the core network equipment is to be used as a basis for an access stratum (AS) security context between the user equipment and radio access network equipment; wherein

the signaling is performed in response to determining that the new NAS security context has been activated, that the new NAS security context is different from a NAS security context on which a currently active AS security context is based, and that the core network equipment has not yet performed an explicit security context modification procedure that prompts the radio access network equipment included in the radio access network and the user equipment to switch to using a new AS security context based on the new NAS security context.

2. The method of claim 1 , wherein the handover procedure is for handover of the user equipment to target radio access network equipment, wherein the method further comprises receiving a path switch request from the target radio access network equipment after the handover procedure, and wherein the signaling comprises, after the handover procedure, transmitting a path switch request acknowledgement message to the target radio access network equipment responsive to the path switch request, wherein the path switch request acknowledgement message includes a field indicating that the new NAS security context is to be used as a basis for the AS security context.

3. The method of claim 2 , wherein the field is a new security context indicator field.

4. The method of claim 1 , wherein the handover procedure is for handover of the user equipment from source radio access network equipment to target radio access network equipment, wherein the core network equipment comprises source core network equipment associated with the source radio access network equipment, and wherein the signaling comprises, during the handover procedure and responsive to receiving a handover required message from the source radio access network equipment, transmitting a forward relocation request message from the core network equipment to target core network equipment associated with the target radio access network equipment, wherein the forward relocation request message includes a field indicating that the new NAS security context is to be used as a basis for the AS security context.

5. The method of claim 1 , wherein the handover procedure is for handover of the user equipment from source radio access network equipment to target radio access network equipment, and wherein the signaling comprises, during the handover procedure, transmitting a handover request message from the core network equipment to the target radio access network equipment, wherein the handover request message includes a field that indicates that the new NAS security context is to be used as a basis for the AS security context.

6. The method of claim 4 , wherein the field is a key change indictor field that indicates a NAS security context key has changed.

7. The method of claim 1 , wherein the core network equipment implements an access and mobility management function, AMF, in a core network.

8. A wireless communication system comprising a core network and a radio access network, wherein the core network comprises the core network equipment comprising processing circuitry, memory and transceiver circuitry, collectively configured to:

switch to using a new non-access stratum, NAS, security context between a user equipment and the core network equipment; and

during or in association with a handover procedure for handover of the user equipment, signal from the core network equipment that the new NAS security context between the user equipment and the core network equipment is to be used as a basis for an access stratum AS security context between the user equipment and radio access network equipment; wherein

the signaling is performed in response to a determination that the new NAS security context has been activated, that the new NAS security context is different from a NAS security context on which a currently active AS security context is based, and that the core network equipment has not yet performed an explicit security context modification procedure that prompts a radio access network equipment included in the radio access network and the user equipment to switch to using a new AS security context based on the new NAS security context.

9. The wireless communication system of claim 8 , wherein the handover procedure is for handover of the user equipment to target radio access network equipment, wherein the core network is further configured to receive a path switch request from the target radio access network equipment after the handover procedure, and wherein the signaling comprises, after the handover procedure, transmitting a path switch request acknowledgement message to the target radio access network equipment responsive to the path switch request, wherein the path switch request acknowledgement message includes a field indicating that the new NAS security context is to be used as a basis for the AS security context.

10. The wireless communication system of claim 9 , wherein the field is a new security context indicator field.

11. The wireless communication system of claim 8 , wherein the handover procedure is for handover of the user equipment from source radio access network equipment to target radio access network equipment, wherein the core network equipment comprises source core network equipment associated with the source radio access network equipment, and wherein the signaling comprises, during the handover procedure and responsive to receiving a handover required message from the source radio access network equipment, transmitting a forward relocation request message from the core network equipment to target core network equipment associated with the target radio access network equipment, wherein the forward relocation request message includes a field indicating that the new NAS security context is to be used as a basis for the AS security context.

12. The wireless communication system of claim 8 , wherein the handover procedure is for handover of the user equipment from source radio access network equipment to target radio access network equipment, and wherein the signaling comprises, during the handover procedure, transmitting a handover request message from the core network equipment to the target radio access network equipment, wherein the handover request message includes a field that indicates that the new NAS security context is to be used as a basis for the AS security context.

13. The wireless communication system of claim 11 , wherein the field is a key change indictor field that indicates a NAS security context key has changed.

14. The wireless communication system of claim 8 , wherein the core network equipment implements an access and mobility management function, AMF, in a core network.

15. Core network equipment configured for use in a core network of a wireless communication system, wherein the wireless communication system comprises the core network and a radio access network, the core network equipment comprising:

processing circuitry and memory, the memory containing instructions executable by the processing circuitry whereby the core network equipment is configured to:

switch to using a new non-access stratum, NAS, security context between a user equipment and the core network equipment; and

during or in association with a handover procedure for handover of the user equipment, signal from the core network equipment that the new NAS security context between the user equipment and the core network equipment is to be used as a basis for an access stratum AS security context between the user equipment and radio access network equipment; wherein

the signaling is performed in response to a determination that the new NAS security context has been activated, that the new NAS security context is different from a NAS security context on which a currently active AS security context is based, and that the core network equipment has not yet performed an explicit security context modification procedure that prompts a radio access network equipment included in the radio access network and the user equipment to switch to using a new AS security context based on the new NAS security context.

16. The core network equipment of claim 15 , wherein the handover procedure is for handover of the user equipment to target radio access network equipment, wherein the core network equipment is further configured to receive a path switch request from the target radio access network equipment after the handover procedure, and wherein the signaling comprises, after the handover procedure, transmitting a path switch request acknowledgement message to the target radio access network equipment responsive to the path switch request, wherein the path switch request acknowledgement message includes a field indicating that the new NAS security context is to be used as a basis for the AS security context.

17. The core network equipment of claim 16 , wherein the field is a new security context indicator field.

18. The core network equipment of claim 15 , wherein the handover procedure is for handover of the user equipment from source radio access network equipment to target radio access network equipment, wherein the core network equipment comprises source core network equipment associated with the source radio access network equipment, and wherein the signaling comprises, during the handover procedure and responsive to receiving a handover required message from the source radio access network equipment, transmitting a forward relocation request message from the core network equipment to target core network equipment associated with the target radio access network equipment, wherein the forward relocation request message includes a field indicating that the new NAS security context is to be used as a basis for the AS security context.

19. The core network equipment of claim 15 , wherein the handover procedure is for handover of the user equipment from source radio access network equipment to target radio access network equipment, and wherein the signaling comprises, during the handover procedure, transmitting a handover request message from the core network equipment to the target radio access network equipment, wherein the handover request message includes a field that indicates that the new NAS security context is to be used as a basis for the AS security context.

20. The core network equipment of claim 18 , wherein the field is a key change indictor field that indicates a NAS security context key has changed.

21. The core network equipment of claim 15 , wherein the core network equipment implements an access and mobility management function, AMF, in a core network.