A method performed by a Serving-Call Session Control Function, S-CSCF (108; 226; 304; 404), comprising: receiving , at the S-CSCF (108; 226; 304; 404), a Session Initiation Protocol, SIP, INVITE message associated with a user equipment, UE; sending , based at least in part on the SIP INVITE message and to a Home Subscriber Server, HSS, a first request for subscriber data; receiving , from the HSS and based at least in part on the first request, the subscriber data, the subscriber data comprising an International Mobile Subscriber Identity, IMSI, associated with the UE; determining whether to query for identity data a Fifth-Generation, 5G, Equipment Identity Register, EIR, (112; 240; 402) using a permanent equipment identifier, PEI, associated with the UE or another EIR using an International Mobile Equipment Identity, IMEI, associated with the UE based at least in part on the IMSI; wherein the 5G-EIR (112; 240; 402) is coupled to an Access and Mobility Management Function, AMF ; sending , based at least in part on the subscriber data and to the 5G-EIR (112; 240; 402) via an N17' interface , a second request for identity data, wherein the N17' interface is configured between the 5G-EIR (112; 240; 402) and the S-CSCF (108; 226; 304; 404) and comprises a Representational State Transfer, REST, HTTP 2.0 interface, wherein the second request includes the PEI; receiving , based at least in part on the second request and from the 5G-EIR (112; 240; 402) via the N17' interface , the identity data, wherein the identity data is based on the PEI and the identity data comprises an indication that the UE is authorized, not authorized, partially authorized, or unknown; and evaluating an authenticity of the UE based at least in part on the identity data., wherein evaluating an authenticity of the UE comprises determining if the UE is associated with at least one of a fraud list, a stolen list, or a blocked list. receiving , at the S-CSCF (108; 226; 304; 404), a Session Initiation Protocol, SIP, INVITE message associated with a user equipment, UE; sending , based at least in part on the SIP INVITE message and to a Home Subscriber Server, HSS, a first request for subscriber data; receiving , from the HSS and based at least in part on the first request, the subscriber data, the subscriber data comprising an International Mobile Subscriber Identity, IMSI, associated with the UE; determining whether to query for identity data a Fifth-Generation, 5G, Equipment Identity Register, EIR, (112; 240; 402) using a permanent equipment identifier, PEI, associated with the UE or another EIR using an International Mobile Equipment Identity, IMEI, associated with the UE based at least in part on the IMSI; wherein the 5G-EIR (112; 240; 402) is coupled to an Access and Mobility Management Function, AMF ; sending , based at least in part on the subscriber data and to the 5G-EIR (112; 240; 402) via an N17' interface , a second request for identity data, wherein the N17' interface is configured between the 5G-EIR (112; 240; 402) and the S-CSCF (108; 226; 304; 404) and comprises a Representational State Transfer, REST, HTTP 2.0 interface, wherein the second request includes the PEI; receiving , based at least in part on the second request and from the 5G-EIR (112; 240; 402) via the N17' interface , the identity data, wherein the identity data is based on the PEI and the identity data comprises an indication that the UE is authorized, not authorized, partially authorized, or unknown; and evaluating an authenticity of the UE based at least in part on the identity data., wherein evaluating an authenticity of the UE comprises determining if the UE is associated with at least one of a fraud list, a stolen list, or a blocked list. <EOS>