# Post-Quantum Key Exchange and Subscriber Identity Encryption in 5G Using ML-KEM (Kyber) 1
## 7 Conclusions and Future Directions  
In this research work, we study the performance analysis of post-quantum (Kyber-512, the only selected KEM cipher by NIST) and pre-quantum (X25519 and secp256r1, currently used for 5G SUCI) ciphers in the identification phase of 5G-AKA during registration. The UE calculates the Subscriber Concealed Identifier (SUCI) and sends it to the CN during the 5G-AKA protocol for registration. In this study, we show that the SUCI calculation, using the post-quantum Kyber-512 at the UE and CN, performs better than the pre-quantum ECIES ciphers. Focusing on the lightweight ciphers for the UE in 5G, the PQC KEM and encryption based on Kyber-512 performs better in computational time and energy consumption than the pre-quantum equivalent. Due to the low energy and time consumption, Kyber-512 has positive effects, including an extended battery life, data transmission, optimized resource utilization, and enhanced overall performance. While we focus specifically on the SUCI calculation operations (which utilize the SIM-hardcoded core network's public key and occur within the UE before the 5G networking) in this research, taking a systems approach to further analyze the rest of the 5G operations can go beyond the scope of this paper. Hands-on implementations of such a 5G networking system, for example, using a software-defined radio and 5G software of srsRAN and Open5 GS, can validate the 5G integration and facilitate practicality. In addition to the validations, such implementation will enable measuring the networking byte size overhead, the communication overhead in terms of initiating the registration request, and the energy consumption of the user equipment within the 5G networking communication session. To measure the scalability of the core network, we plan to measure the maximum number of subscriber identifications that the core network can carry out with the three ciphers (Kyber-512, X25519, and secp256r1) and compare the latency and throughput of network communication. While our work simulated and emulated mobile devices using a Raspberry Pi and Mini-PC, we can further use a jail-broken phone or an embedded software, which is mobile-device friendly. For example, the wolfSSL-embedded TLS library is a lightweight and portable SSL/TLS library. It is specifically designed for IoT, embedded, and real-time operating system (RTOS) environments, prioritizing a small size, high speed, and comprehensive features. wolfSSL supports the ECIES with elliptic curves defined by NIST, which can be compromised by quantum computers. While our research focuses on the current 5G New Radio technology (and shows that it supports the NIST-standardized, post-quantum Kyber), we expect this research to inform the future designs and incorporation of post-quantum ciphers in the next generations of mobile networking (beyond 5G and 6G). The post-quantum Kyber can have comparable or even better time/power performances than the ECIES; however, it introduces additional byte overheads in storing the public key and in transmitting the ciphertext. Conceptualization, Q.K. and S.P. ; Methodology, Q.K. and S.P. ; Software, S.P. ; Validation, Q.K., S.P. and S.-Y.C. ; Formal analysis, Q.K. and S.-Y.C. ; Investigation, Q.K., S.P. and S.-Y.C. ; Resources, Q.K. and S.-Y.C. ; Data curation, S.P. ; Writing--original draft, Q.K. and S.-Y.C. ; Writing--review & editing, Q.K. and S.-Y.C. ; Visualization, Q.K. ; Supervision, S.-Y.C. ; Project administration, S.-Y.C. All authors have read and agreed to the published version of the manuscript. This research received no external funding  
The data presented in this study are openly available in the GitHub public repository. This work extends our previous conference paper [50]. In addition to the overall presentation and writing-based improvements, we extend our conference paper by including a security evaluation and side-channel attacks targeting NIST-selected post-quantum algorithms.