Figure 5-1 shows the functional security model for the CAPIF architecture. The interfaces CAPIF-1, CAPIF-1e, CAPIF-2, CAPIF-2e, CAPIF-3, CAPIF-4, CAPIF-5, CAPIF-3e, CAPIF-4e, CAPIF-5e, CAPIF-7 and CAPIF-7e are defined in TS 23.222 and support the CAPIF functionality defined in TS 23.222. CAPIF-1, CAPIF-2, CAPIF-3, CAPIF-4, CAPIF-5 and CAPIF-7 are interfaces that lie within the PLMN trust domain while the CAPIF-1e , CAPIF-2e, CAPIF-3e, CAPIF-4e, CAPIF-5e and CAPIF-7e interfaces are CAPIF core and AEF access points for API Invokers outside of the PLMN trust domain. Security for the CAPIF-1, CAPIF-2, CAPIF-3, CAPIF-4, CAPIF-5 and CAPIF-7 interfaces support TLS and are defined in subclauses 6.2, 6.4 and 6.6 of the present document. Security for the CAPIF-1e, CAPIF-2e and CAPIF-7e interfaces support TLS, and are defined in subclause 6.3, subclause 6.5, and subclause 6.9 respectively. Security for the CAPIF-3e, CAPIF-4e and CAPIF-5e interfaces support NDS/IP security to secure communication between different IP security domains. This avoids multiple secure connections between API provider domain and CAPIF core domain by leveraging the NDS/IP security procedures specified in TS 33.210. Authentication and authorization are required for both API invokers that lie within the PLMN trust domain and API invokers that lie outside of the PLMN trust domain. For an API invoker that is outside of the PLMN trust domain, the CAPIF core function in coordination with the API exposing function utilizes the CAPIF-1e, CAPIF-2e and the CAPIF-3 interfaces to onboard, authenticate and authorize the API invoker prior to granting access to CAPIF services. Security flow diagrams for onboarding security, CAPIF-1e security and CAPIF-2e security can be found in Annex B. When the API invoker is within the PLMN trust domain, the CAPIF core function in coordination with the API exposing function perform authentication and authorization of the API invoker via the CAPIF-1, the CAPIF-2 and the CAPIF-3 interfaces prior to granting access to CAPIF services. Authentication and authorization of API invokers (both internal and external to the PLMN trust domain) is specified in clause 6 of the present document.