Section: 6.6.4.3 UP integrity mechanisms between the UE and the ng-eNB
Content: If the UE supports E-UTRA connected to 5GC, the UE shall indicate support of integrity protection by setting the EIA7 algorithm bit in 5G UE Security Capability IE (see clause 9.11.3.54 of TS 24.501[ Non-Access-Stratum (NAS) protocol for 5G System (5GS); Stage 3 ]  [35]) to indicate that the UE supports user plane integrity protection with an ng-eNB. If the 128-NIA algorithm is signalled by the ng-eNB to the UE, clause 6.6.4.2 applies. If the 128-EIA algorithm is signalled by the ng-eNB to the UE, the following applies: - The use and mode of operation of the 128-EIA algorithms are specified in Annex B of TS 33.401[ 3GPP System Architecture Evolution (SAE); Security architecture ]  [10]. - The input parameters to the 128-bit EIA algorithms as described in Annex B of TS 33.401[ 3GPP System Architecture Evolution (SAE); Security architecture ]  [10] are, the message packet, a 128-bit integrity key KUPint as KEY, a 5-bit bearer identity BEARER value of which is assigned as specified by TS 38.323[ NR; Packet Data Convergence Protocol (PDCP) specification ]  [23], the 1-bit direction of transmission DIRECTION, and a bearer specific, time and direction dependent 32-bit input COUNT which corresponds to the 32-bit PDCP COUNT. NOTE: The ng-eNB decides whether to signal 128-NIA or 128-EIA algorithm (cf. clause 5.3.1.2 of TS 36.331[ Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification ]  [69]). If the ng-eNB or the UE receives a PDCP PDU which fails integrity check with faulty or missing MAC-I after the start of integrity protection, the PDU shall be discarded. UE and the ng-eNB (or the ng-eNB acting as the MN) shall derive UP integrity key as specified in Annex A.7 of TS 33.401[ 3GPP System Architecture Evolution (SAE); Security architecture ]  [10], with the KeNB set to KgNB.