Question: What parameters are used to form the input S to the Key Derivation Function (KDF) when deriving a KSEAF from KAUSF?
Option 1: FC = 0x6C, P0 = serving network name, L0 = length of serving network name, and KEY = KAUSF
Option 2: FC = 0x5A, P0 = UE identifier, L0 = length of UE identifier, and KEY = KSEAF
Option 3: FC = 0x6C, P0 = serving PLMN ID, L0 = length of serving PLMN ID, and KEY = KAUSF
Option 4: FC = 0x5A, P0 = serving network name, L0 = length of serving network name, and KEY = KSEAF
Explanation: When deriving a KSEAF from KAUSF, the input S to the KDF is formed using specific parameters. The correct parameters are FC = 0x6C (a fixed value), P0 = serving network name (constructed as specified in clause 6.1.1.4), L0 = length of serving network name, and KEY = KAUSF (the input key). These parameters ensure the secure derivation of KSEAF from KAUSF.