Section: A.19 UPU-MAC-IAUSF generation function
Content: When deriving a UPU-MAC-IAUSF from KAUSF, the following parameters shall be used to form the input S to the KDF. - FC = 0x7B, - P0 = UE Parameters Update Data, i.e. UE parameters update list as given in clause 9.11.3.53A of TS 24.501[ Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3 ]  [35] (starting from octet 23), - L0 = length of UE Parameters Update Data - P1 = CounterUPU - L1 = length of CounterUPU The input key Key shall be KAUSF. The UPU-MAC-IAUSF is identified with the 128 least significant bits of the output of the KDF.