A.3 A-TID derivation function

33.5353GPPAuthentication and Key Management for Applications (AKMA) based on 3GPP credentials in the 5G System (5GS)Release 17TS

When deriving the A-TID from K_AUSF, the following parameters shall be used to form the input S to the KDF:

– FC = 0x81;

– P0 = "A-TID";

– L0 = length of "A-TID"; (i.e. 0x00 0x05)

– P1 = SUPI;

– L1 = length of SUPI.

The input key KEY shall be K_AUSF.

SUPI shall be the same value as parameter P0 in Annex A.7.0 of TS 33.501 [2].