A.19 UPU-MAC-I_AUSF generation function

33.5013GPPRelease 18Security architecture and procedures for 5G SystemTS

When deriving a UPU-MAC-I_AUSF from K_AUSF, the following parameters shall be used to form the input S to the KDF.

– FC = 0x7B,

– P0 = UE Parameters Update Data,

– L0 = length of UE Parameters Update Data

– P1 = Counter_UPU

– L1 = length of Counter_UPU

The input key Key shall be K_AUSF.

The UPU-MAC-I_AUSF is identified with the 128 least significant bits of the output of the KDF.