 the NAS request and identity of the mobile are transferred from the 5G base station to the core network (AMF: Access and Mobility Management Function). The AKA (Authentication and Key Agreement) mechanism has been defined to allow the mutual authentication of third parties and distribution of keys when attaching the mobile to the 5G mobile network. Mutual authentication is based on the AUTN (Authentication Network) and RES (Result) seals generated by the UDM (Unified Data Management) entity and by the mobile. Authentication is based on a RAND sequence and a secret key Kj. The RAND sequence is generated by the UDM entity and is transmitted to the MME, which then forwards it to the UE. The secret key K is stored in the USIM module of the UE's UICC (Universal Integrated Circuit Card) and is provisioned in the UDM entity when the subscription is taken out. The activation of NAS security is performed by calculating the encryption and integrity key for the exchange of messages between the AMF function and the mobile. NG-RAN Network - Procedures 3.2.3.2. Registration and access to service After the activation of NAS security, the AMF function retrieves all of the authorized mobile services (authorized NSSAI) that are provisioned in the UDM. Depending on the location of the user, the AMF function also retrieves the service access policy rules. The AMF function then proceeds the activation of security on the radio bearer. The activation of AS security is intended to protect the radio interface: - with the integrity and ciphering of RRC signaling messages; - with the integrity of the traffic data (optional); - by ciphering the traffic data. When the mobile confirms the activation of the radio bearer, the context of the mobile is registered in the AMF function. 3.2.3.3. Description of the registration procedure The registration procedure is described in Figures 3.9 and 3.10. 1) The registration procedure is triggered by the mobile. After the establishment of the signaling radio bearer, the mobile sends the dedicated NAS me