## 7 Discussion  
The AKMA integrated with TLS 1.3 PSK protocols offers a flexible framework for securing IoT systems, particularly in resource-constrained environments. However, the trade-offs between security, efficiency, and latency inherent in the three modes--PSK-only,  
Figure 11: Network Latency according to packet loss ratio. Figure 10: CPU usage by the AKMA TLS 1.3 PSK modes. PSK-(EC)DHE, and 0-RTT--require careful evaluation. Our experimental results reveal a shared vulnerability among these modes to signaling-level replay attacks, stemming from the lack of freshness mechanisms in the ClientHello message. The PSK-only mode is the most lightweight and efficient, making it suitable for resource-constrained IoT devices. However, its lack of perfect forward secrecy poses significant risks, mainly when a long-term key compromise is possible. Without PFS, the confidentiality of all past communications is jeopardized if the long-term key is compromised, rendering this mode unsuitable for applications where data integrity and confidentiality are paramount, such as healthcare IoT or Industrial IoT (IIoT). The 0-RTT mode reduces latency, making it highly advantageous for real-time applications such as CCTV surveillance or connected vehicles. However, its efficiency comes at the cost of security, as the inclusion of application data piggybacked in the ClientHello message exposes it to data-level replay attacks. Furthermore, its limited PFS weakens its suitability for applications requiring long-term confidentiality. While the mode is attractive for latency-sensitive operations, its vulnerabilities to replay attacks limit its adoption in high-security IoT scenarios, emphasizing the need for mechanisms to ensure freshness and mitigate replay risks. The PSK-(EC)DHE mode demonstrates the strongest security features among the three modes. It provides confidentiality, integrity, mutual authentication, secure key exchange, and Perfect Forward Secrecy, making it the most secure option for IoT environments. Despite these strengths, the mode remains vulnerable to signaling-level replay attacks, which could undermine system integrity in critical applications. Its relatively higher computational demands make it more suitable for medium- to high-security IoT scenarios where security precedes latency, such as healthcare IoT and IIoT. These modes highlight the intricate trade-offs between security, performance, and resource constraints when applied to diverse IoT scenarios. Examples include the following:  
* In smart homes, PSK-only or 0-RTT modes may suffice for routine, non-critical operations like monitoring temperature or controlling lights, where efficiency outweighs the need for robust security. PSK-(EC)DHE mode would be more appropriate for critical devices like smart locks or cameras. * In healthcare IoT, patient data confidentiality and integrity necessitate using PSK-(EC)DHE mode despite its replay attack vulnerability. This mode's secure key exchange and perfect forward secrecy ensure robust protection for sensitive medical applications. * In industrial IoT (IIoT), PSK-(EC)DHE is preferred for protecting control systems and ensuring operational continuity. However, its susceptibility to replay attacks highlights the need for future enhancements to address these risks in critical infrastructure. * For CCTV surveillance, the 0-RTT mode provides an optimal balance of performance and security as long as anti-replay measures are implemented to safeguard the integrity of real-time video streams. In the 5G secondary authentication, AKMA, as proposed by 3 GPP, and EAP [23], as proposed by IETF, represent key standards that have undergone substantial development. Table 5 summarizes the authentication operations based on various options within the AKMA and EAP frameworks. Analysis reveals that AKMA performs fewer operations than EAP by leveraging credentials derived from the initial authentication. Consequently, AKMA is demonstrated to be a more efficient authentication mechanism compared with the EAP framework.