A.20 UPU-MAC-I_UE/UPU-XMAC-I_UE generation function

33.5013GPPRelease 18Security architecture and procedures for 5G SystemTS

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

– FC = 0x7C,

– P0 = 0x01 (UPU Acknowledgement: Verified the UE Parameters Update Data successfully)

– L0 = length of UPU Acknowledgement (i.e. 0x00 0x01)

– P1 = Counter_UPU

– L1 = length of Counter_UPU

The input key Key shall be K_AUSF.

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