Question: What are the parameters used to form the input S to the Key Derivation Function (KDF) when deriving a SoR-MAC-IUE/SoR-XMAC-IUE from KAUSF?
Option 1: FC = 0x78, P0 = 0x00, L0 = length of SoR Acknowledgement, P1 = CounterSoR, L1 = length of CounterSoR
Option 2: FC = 0x01, P0 = 0x78, L0 = length of KAUSF, P1 = SoR Acknowledgement, L1 = length of SoR Acknowledgement
Option 3: FC = 0x00, P0 = 0x78, L0 = length of CounterSoR, P1 = KAUSF, L1 = length of KAUSF
Option 4: FC = 0x78, P0 = 0x01, L0 = length of SoR Acknowledgement, P1 = CounterSoR, L1 = length of CounterSoR
Explanation: The correct parameters used to form the input S to the KDF are FC = 0x78, P0 = 0x01 (SoR Acknowledgement: Verified the Steering of Roaming Information successfully), L0 = length of SoR Acknowledgement, P1 = CounterSoR, and L1 = length of CounterSoR. These parameters are used to derive a SoR-MAC-IUE/SoR-XMAC-IUE from KAUSF in 5G systems.