The 5th Generation Mobile Communication (5G) plays a significant role in the Fourth Industrial Revolution (4IR), facilitating significant improvements and innovations in various fields. The 3rd Generation Partnership Project (3GPP) is currently standardizing the Authentication and Key Management for Application (AKMA) system for the 5G convergence applications (5G cAPPs). The Transport Layer Security (TLS) is recommended as the application-specific Ua* protocol between User Equipment (UE) and Application Function (AF) to securely transmit the AKMA identifiers of UE as well as guarantee traffic protection. Among TLS protocols, session resumption in TLS 1.2 and the Pre-Shared Key (PSK) modes of TLS 1.3 are particularly desirable for Ua*. Unfortunately, the integration of PSK options of TLS 1.3, namely PSK-only, PSK-(EC)DHE, and 0-RTT (0 Round-Trip Time) modes, with AKMA has not yet been thoroughly investigated; hence, security, performance, compatibility, and effectiveness remain uncertain. In response, this paper explores the integration of the TLS 1.3 PSK options with AKMA and investigates the said metrics by conducting formal security verification and emulating exemplary applications. According to the formal verification and experimental results, the PSK-(EC)DH mode shows a security strength trade-off with efficiency. On the one hand, the 0-RTT mode demonstrates better efficiency but exhibits drawbacks on forward secrecy and replay attacks. The result suggests that 0-RTT mode has to be approved to ensure seamless integration of the TLS 1.3 PSK option with AKMA. In addition, adjustment on the AKMA architecture is also imperative to enhance security level.

This study investigates performance overheads and security threats in 6th Generation Mobile Communication (6G) roaming environments, which are expected to enable services such as autonomous driving, smart cities, and remote healthcare that demand ultra-low latency and high reliability. To bridge the gap between standardization and real-world deployment, we built a realistic roaming testbed by separating the home and visited public land mobile networks (H-PLMN and V-PLMN) and simulating user equipment (UE) interactions. In this environment, we defined and measured roaming cost by comparing non-roaming and roaming procedures, and reproduced two Subscription Concealed Identifier (SUCI)-based denial-of-service (DoS) attacks: random generation and replay. Our experiments showed that intermediary functions such as the Security Edge Protection Proxy (SEPP) and Service Communication Proxy (SCP) introduced CPU/memory overhead and latency, highlighting performance degradation unique to roaming. Moreover, random SUCI generation concentrated load on the Authentication Server Function (AUSF) in the H-PLMN, whereas replay attacks distributed it across both the H-PLMN and the V-PLMN, consistently identifying the AUSF as a bottleneck. These findings demonstrate that roaming enlarges the attack surface and exposes vulnerabilities not fully addressed in current standards. We conclude that secure and reliable 6G roaming requires multi-layered defense strategies with inter-operator cooperation, providing empirical evidence to guide standardization and operational practice.