Recent advances in nanoelectronics have spurred increased interest in the human brain and its complex functions. Numerous studies have explored brain behavior in varying levels of detail, from individual neurons to entire lobes. Intricately structured, the brain is a complex organ susceptible to diseases that may disrupt the connectivity between its internal regions. Investigating this phenomenon, the present study applies a discrete finite-state model to map the behavior of neurons within a neuronal agglomerate and examine the effect of disease on these behaviors. Each agglomerate is then compared to a wireless clustered network and modeled as a finite-state system, with inter-cluster communications analyzed under conditions of temporal variations and degradation. This work represents one of the most advanced applications of discrete finite-state processes and routing theory in brain modeling.

Entanglement-based quantum key distribution (QKD) offers robust key distribution through intrinsically correlated measurements, ensuring that any eavesdropping attempt introduces detectable disturbances. Although practical implementations are primarily limited to fixed fiber networks, extending QKD to mobile platforms like drones or small satellites introduces challenges in optical alignment, weight, and power consumption. This work outlines the core components and architecture for implementing BBM92-based QKD in mobile settings. A compact polarization Sagnac interferometer that utilizes a periodically poled potassium titanyl phosphate crystal provides a stable and efficient method for generating entangled photon pairs. The supporting subsystems include a polarization compensation system, detector module, and an acquisition, pointing, and tracking (APT) system. To assess performance under realistic conditions, we simulate photon loss, detector efficiency, and quantum bit error rates (QBERs) using the Simulator for Quantum Networks and Channels framework. The results show an average key generation rate of 5.43 bits/s, a final secure key length of 45.27 bits per block, and a QBER of 4.5%.

The integration of quantum key distribution (QKD) into data centers represents a promising advance in secure communications. As cyber threats evolve and the volume of sensitive information grows, strengthening intra-data center security has become a strategic necessity for ensuring confidentiality and operational resilience. This paper explores the application of an entanglement-based QKD method for securing intra-connectivity within data centers, focusing on deploying the BBM92 protocol in a controlled environment. We detail the system architecture, technical requirements, and operational considerations, and we report simulation results from a 100-block BBM92 run: an average sifted key of 1224 bits per block, with 25% used for QBER estimation, reconciliation disclosures of 352 bits, and privacy amplification removing an additional 13 bits, yielding a final secure key of 554 bits per block at an average rate of 52 bps. Across the run, 86 keys were delivered to applications, enabling 43 IKEv2/IPsec sessions, with an initial ramp-up before reaching steady, near-linear key service. These findings indicate that entanglement-based QKD can provide robust, quantum-safe key distribution for data center environments while highlighting practical integration challenges and performance trade-offs.

The rapid advancement of quantum computing presents an urgent threat to 5G networks, particularly across sensitive roaming boundaries. While existing quantum-safe solutions typically require intrusive modifications to core network functions, this paper introduces a highly crypto-agile, non-intrusive proxy architecture to secure the N32 control-plane and N9 user-plane roaming interfaces. By deliberately isolating cryptographic operations within local, containerized proxies, our design avoids complex dependency upgrades on the running 5G core. To maximize practical deployability, we developed proof-of-concept prototypes based on OpenSSL 3.5.4 offering two distinct, highly configurable variants. The first enables immediate, software-only integration utilizing Post-Quantum Cryptography (PQC) suites (ML-KEM/ML-DSA, BIKE/Falcon). The second deploys autonomous agents in a custom Pre-Shared Key (PSK) configuration fed by out-of-band Quantum Key Distribution (QKD), enabling dynamically enforced cryptoperiods and seamless Public Key Infrastructure (PKI) fallback mechanism based on real-time key availability. We evaluate this architecture using a comprehensive open-source testbed combining Open5GS and QKDNetSim. To assess practical deployability, we measured control-plane registration times, cryptographic data volume, user-plane delay, and QKD key consumption against legacy HTTP(S) baselines. Experimental results demonstrate that these quantum-safe architectures perform comparably to, or better than, legacy security. The PQC proxies maintained competitive cold-start registration times (261–285 ms), successfully balancing computational and bandwidth trade-offs. Notably, the QKD-assisted PSK configuration achieved the highest efficiency, reducing median registration time to 258.2 ms (a 4.5% improvement over legacy HTTPS) and restricting handshake data volume to 12.3 kB by bypassing heavy asymmetric certificate authentication. Furthermore, all prototypes successfully secured the traditionally unencrypted GPRS Tunnelling Protocol user plane (GTP-U) traffic traversing the N9 interface with a practically negligible delay increase ( $\sim 300~\mu $ s). Finally, the study highlights critical transport-layer constraints, such as TCP-in-TCP congestion interference, underscoring the necessity of DTLS 1.3 to optimize practical, quantum-resilient telecommunications infrastructure.

Key management strategies are a critical yet often overlooked aspect of integrating quantum key distribution (QKD) networks as a service into critical infrastructure. It has a considerable impact on the efficiency of QKD network services, thereby shaping its suitability for diverse applications. In this paper, we examine the effectiveness of key management strategies developed through practical testbeds, identifying their strengths and weaknesses. A novel, to the best of our knowledge, organization of key storage to enhance key construction efficiency and overall service performance is introduced. Using simulation tools, the proposed strategy is evaluated against existing approaches, demonstrating superior performance and effectiveness.

This paper presents a vendor-agnostic architecture for secure pre-shared key (PSK) exchange between Quantum Key Distribution (QKD) nodes, leveraging post-quantum cryptography (PQC) tools. The proposed system combines PQC-OpenVPN and OQS-OpenSSH with USB mass storage emulation and single-board computers (SBCs) to automate the transfer of initial authentication secrets. This design significantly reduces manual intervention and mitigates risks associated with physical key handling. The solution was experimentally validated on IDQ Clavis3 and Cerberis3 devices and is broadly applicable to other QKD platforms that support only USB-based key input. Integration of lattice-based algorithms such as Kyber, Dilithium, and ML-DSA enables encapsulation and authentication of quantum-safe keys. Furthermore, a layered design using VPN and SSH channels provides robust cryptographic isolation for authentication material in transit. The work contributes a reproducible and cost-effective testbed for post-quantum hardened QKD deployments and demonstrates the practical feasibility of combining PQC mechanisms with QKD systems to enhance trust in future quantum-safe infrastructures.

Network emulators are essential in testing network systems, applications, and protocols. Emulators bridge the gap between simulation setups that lack realism in results and real-world trials that are accurate but often expensive, non-reproducible, and uncontrollable. This paper describes the simulations and emulations of the national Czech QKD network. Using emulation techniques, a unique ecosystem is formed that includes the processes of generating, processing, storing, and consuming cryptographic keys. The presented tool will undoubtedly spur future development, understanding, and teaching, and it is critical for testing novel applications and protocols applied to QKD networks.

Quantum Key Distribution (QKD), a secret key agreement primitive, makes possible long-awaited real-world Information-Theoretical Security (ITS). In the last twenty years, the development of QKD-based networks that deliver ITS keys to distant parties has been a focus of the academic and industry sectors. Several key-delivery specifications have been developed for the practical delivery of keys to end applications. In this paper, we discuss key-delivery specifications with a focus on security and authentication.