A.8 Calculation of K_NRP for UE-to-Network relays

33.5033GPPRelease 17Security Aspects of Proximity based Services (ProSe) in the 5G System (5GS)TS

When calculating K_NRP from UP-PRUK, the following parameters shall be used to form the input S to the KDF that is specified in Annex B of TS 33.220 [5]:

– FC = 0x8A

– P0 = Relay Service Code

– L0 = length of Relay Service Code (i.e. 0x00 0x03)

– P1 = K_NRP freshness parameter 1

– L1 = length of K_NRP freshness parameter 1 (i.e. 0x00 0x10)

– P2 = K_NRP freshness parameter 2

– L2 = length of K_NRP freshness parameter 2 (i.e. 0x00 0x10)

The input key shall be the 256-bit UP-PRUK.