A.18 SoR-MAC-I_UE/SoR-XMAC-I_UE generation function

33.5013GPPRelease 18Security architecture and procedures for 5G SystemTS

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

– FC = 0x78,

– P0 = 0x01 (SoR Acknowledgement: Verified the Steering of Roaming Information successfully),

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

– P1 = Counter_SoR,

– L1 = length of Counter_SoR.

The input key KEY shall be K_AUSF.

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