A.21 K_AMF to K_{ASME_SRVCC} derivation for interworking

33.5013GPPRelease 18Security architecture and procedures for 5G SystemTS

This input string is used when there is a need to derive K_{ASME_SRVCC} from K_AMF during SRVCC from 5G to UTRAN CS. The following input parameters shall be used.

– FC = 0x7D

– P0 = NAS Downlink COUNT value

– L0 = length of NAS Downlink COUNT value (i.e. 0x00 0x04)

The input key KEY shall be K_AMF.