## 8 Conclusions
### Future Work  
The first research direction focuses on the development of quantum-resistant zero-trust mechanisms. The proposed technical approach involves the integration of post-quantum cryptographic algorithms into ZTAs, specifically by incorporating CRYSTALS-Kyber for key exchange and Falcon for digital signatures into ZTA workflows. Additionally, hybrid stateful hash-based signatures such as XMSS and LMS will be employed to enable quantum-safe key rotation, while lattice-based homomorphic encryption will be explored for secure runtime attestation. The expected outcomes of this work are summarized in Table 22, which outlines the target metrics for authentication latency, key size, and Shor resistance. For instance, the goal is to maintain authentication latency below 25 ms while ensuring 128-bit post-quantum security, albeit at the cost of increasing key size from 256 bit ECC to 1.5 kB Kyber-768. However, several challenges are anticipated, including a 4.2\(\times\) increase in key storage requirements, the complexity of integrating these mechanisms into existing ETSI NFV MANO frameworks, and ensuring backward compatibility with legacy 5G components. The second research direction involves the advancement of cross-domain FL frameworks. This will be achieved by combining multi-party computation using the SPDZ protocol with Blockchain-anchored differential privacy mechanisms leveraging zk-SNARKs. Furthermore, domain-specific normalization layers will be incorporated into the ResNet-152 architecture to account for heterogeneity in data distributions. The anticipated benefitsof this approach include significant accuracy improvements across critical application domains such as healthcare, telecommunications, and smart grids, as illustrated in Figure 23. The figure demonstrates that the proposed cross-domain FL framework is expected to outperform baseline FL models, achieving up to 91% accuracy in the telecom domain. Nevertheless, this direction also introduces several challenges, including ensuring regulatory compliance for cross-border data flows under GDPR and HIPAA, managing the complexities of non-IID data distributions across domains, and addressing the 1.8\(\times\) increase in per-round communication overhead introduced by the proposed protocols. Finally, the overall research roadmap for the next three years is depicted in Figure 24. The plan begins with the development of a prototype for quantum-resistant ZTAs in 2024, focusing on integrating the proposed mechanisms into OpenSSL 3.0 and aligning with NIST PQC standards. In 2025, efforts will shift toward the deployment of a cross-domain FL testbed that combines 5G and healthcare use cases, ensuring inter-domain differential privacy with an \(\epsilon\) parameter below 1.0. The final phase, targeted for 2026, will focus on deploying quantum-safe Radio Intelligent Controllers (RICs) with a goal of achieving Q-Day resilience certification. This roadmap is designed to progressively enhance the security, privacy, and resilience of next-generation networks in anticipation of the emerging quantum threat landscape. Figure 23: Target accuracy improvements across domains. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Metric** & **Current** & **Target** \\ \hline Auth. Latency & 12 ms & \textless{}25 ms (PQ-CRATE) \\ Key Size & 256b ECC & 1.5 kB Kyber-768 \\ Shor Resistance & Vulnerable & 128-bit PQ Security \\ \hline \hline \end{tabular}
\end{table} 
Table 22: Quantum-ZTA security targets. In conclusion, the proposed framework represents a significant step toward enhancing the security, privacy, and performance of O-RAN systems. By integrating innovative techniques in energy optimization, zeroptrust access control, and privacy-preserving FL, our work lays the foundation for the next generation of secure and efficient communication networks. As the demands of 5G and beyond continue to grow, our framework offers a scalable solution that ensures robust, reliable, and privacy-respecting network operations, paving the way for the future of secure edge intelligence.