AS Security Mode Command

RRC Security Activation

After NAS security is established, the gNB activates Access Stratum security using the RRC Security Mode Command. The KgNB key, derived from KAMF, is sent from the AMF to the gNB during the Initial Context Setup procedure. The gNB then derives four keys from KgNB: KRRCint and KRRCenc for RRC signaling protection, and KUPint and KUPenc for user-plane protection. The gNB selects the AS encryption and integrity algorithms and sends the SecurityModeCommand RRC message to the UE.