A.15 K_ASME to K_AMF‘ derivation for interworking

33.5013GPPRelease 18Security architecture and procedures for 5G SystemTS

A.15.1 Idle mode mobility

This input string is used when there is a need to derive K_AMF‘ from K_ASME during mapping of security contexts from EPS to 5G at idle mode mobility. The following input parameters shall be used.

– FC = 0x75

– P0 = NAS Uplink COUNT value of the TAU message included in the Registration Request message

– L0 = length of NAS Uplink COUNT value of the TAU message included in the Registration Request message (i.e. 0x00 0x04)

The input key KEY shall be K_ASME.

A.15.2 Handover

This input string is used when there is a need to derive K_AMF‘ from K_ASME during mapping of security contexts from EPS to 5G at handovers. The following input parameters shall be used.

– FC = 0x76

– P0 = NH value

– L0 = length of NH value (i.e. 0x00 0x20)

The input key KEY shall be K_ASME.