In the burgeoning era of quantum communications, Internet of Things (IoT) devices in high-speed train (HST) environments encounter formidable challenges. These devices are constrained by limited power and computational capabilities while needing to safeguard their data and communications against adversaries equipped with quantum-grade computational power. To counter such threats, Quantum Key Distribution (QKD) emerges as a vital solution, facilitating secure communication between servers and IoT controllers, thereby shielding the more vulnerable IoT sensors. This paper delves into the application of QKD within the unique scenario of HSTs, employing Free Space Optics (FSO) to establish high data rate communication channels. Our experimental setup involves the integration of FSO links for photon exchange essential to QKD. We meticulously explore the QKD process in the context of HSTs, detailing our methodology that involves the alignment of FSO transceivers on ground base stations with those on the moving trains, thereby enabling efficient photon exchange. The study presents quantitative results demonstrating that this approach allows for the exchange of a substantial number of keys, with negligible impact on FSO data throughput. These findings highlight that our proposed method can significantly enhance IoT communication security in HSTs without compromising the Quality of Service (QoS) offered to train passengers. Furthermore, we assess the system’s performance under various visibility conditions, which is crucial for FSO viability. Our results indicate the robustness of the proposed QKD method in diverse operational scenarios, underlining its practical applicability in securing IoT communications within HST environments. Through this study, we provide a comprehensive understanding of implementing QKD in high-speed mobile settings, contributing valuable insights into its effectiveness and feasibility.
In the burgeoning era of quantum communications, Internet of Things (IoT) devices in high-speed train (HST) environments encounter formidable challenges. These devices are constrained by limited power and computational capabilities while needing to safeguard their data and communications against adversaries equipped with quantum-grade computational power. To counter such threats, Quantum Key Distribution (QKD) emerges as a vital solution, facilitating secure communication between servers and IoT controllers, thereby shielding the more vulnerable IoT sensors. This paper delves into the application of QKD within the unique scenario of HSTs, employing Free Space Optics (FSO) to establish high data rate communication channels. Our experimental setup involves the integration of FSO links for photon exchange essential to QKD. We meticulously explore the QKD process in the context of HSTs, detailing our methodology that involves the alignment of FSO transceivers on ground base stations with those on the moving trains, thereby enabling efficient photon exchange. The study presents quantitative results demonstrating that this approach allows for the exchange of a substantial number of keys, with negligible impact on FSO data throughput. These findings highlight that our proposed method can significantly enhance IoT communication security in HSTs without compromising the Quality of Service (QoS) offered to train passengers. Furthermore, we assess the system’s performance under various visibility conditions, which is crucial for FSO viability. Our results indicate the robustness of the proposed QKD method in diverse operational scenarios, underlining its practical applicability in securing IoT communications within HST environments. Through this study, we provide a comprehensive understanding of implementing QKD in high-speed mobile settings, contributing valuable insights into its effectiveness and feasibility.
The emergence of massive, latency-sensitive Internet of Things (IoT) and high-mobility services in 6G networks amplifies long-standing limits of radio systems (bandwidth, interference, Doppler fragility) and exposes classical cryptography to quantum threats. This dissertation presents a framework that integrates Quantum Key Distribution (QKD) with Free-Space Optics (FSO) to provide quantum-resilient connectivity, while exploring applications to terrestrial Internet of Things (IoT), high-speed trains (HST), ultra-high-speed trains (UHST), and non-terrestrial networks (NTN) with high-altitude platforms (HAPs). On the physical layer, we build weather- and turbulence-aware FSO models (attenuation, beam propagation, pointing/beam-wander, scintillation) and derive fundamental link budgets. A core innovation for mobility is an optimization framework that maximizes the distance between base stations along a rail corridor subject to stringent Gbps-class data rate and availability constraints. This front-end optimization directly informs the subsequent design of robust FSO architectures and handover mechanisms for HST/UHST. The resulting system-achieved through divergence control, advanced acquisition-tracking-pointing (ATP), and geometry-aware handover zones-significantly reduces infrastructure density while sustaining high-capacity links. For IoT security, we propose two practical QKD delivery modes (rail-side and onboard) and quantify energy per secret bit and realistic key provisioning. For extended reach, we introduce HAP-assisted QKD via a standards-aligned trusted relay and a composable finite-key decoy-state pipeline using the Entropy Accumulation Theorem. A key contribution is a symmetry-aware altitude optimizer that selects the HAP height to bound the transmittance gap, complete with concavity proofs and implementable solvers. We show that-under realistic HAP turbulence-advanced measurement-device-independent (MDI-), twin-field (TF-), and Gaussian-modulated coherent-state continuous-variable (GM-CV-) QKD protocols all collapse, whereas the simpler per-hop BB84 with decoys remains feasible under finite-key constraints. Results include rate/feasibility maps, robust operating rules, and integrated "security dashboards," complemented by ML-based attacker detection. The framework adheres to tight size-weight-power (SWaP) constraints by prioritizing geometric control and efficient solvers over hardware escalation. Collectively, this dissertation bridges physics, security, and control into a deployable blueprint for quantum-secure communications, advancing FSO for HSTs/UHSTs through optimized base-station placement and highvelocity handovers to minimize infrastructure costs.
The rapid proliferation of Internet of Things devices (IoT) across healthcare, smart homes, transportation, and industrial automation has led to an unprecedented exchange of sensitive data over wireless channels, exposing these networks to cyberattacks, eavesdropping, and unauthorized access.Conventional cryptographic techniques, which rely on computational hardness assumptions, are increasingly vulnerable to the emerging capabilities of quantum computing.This paper explores the application of Quantum Key Distribution (QKD) as a means of enabling secure and dependable data communication for IoT devices.By exploiting the fundamental principles of quantum mechanics, QKD allows two communicating parties to generate a shared secret key while inherently detecting any attempt at interception.The proposed approach aims to enhance data privacy, ensure secure authentication, preserve confidentiality, and safeguard IoT systems against present and future quantum enabled threats.The integration of quantum based security techniques into existing IoT infrastructure is examined, along with its implications for improving the reliability and trustworthiness of wireless IoT communication systems.This work positions Quantum Enhanced Secure Data Communication as a forward looking security solution for next generation IoT networks.
The exponential growth of the Internet of Things (IoT) and its integration into critical infrastructures has elevated the need for robust and future-proof security mechanisms. Traditional cryptographic systems, while effective today, are increasingly vulnerable to advancements in quantum computing. This paper explores the integration of Quantum Key Distribution (QKD) as a novel security paradigm for next-generation IoT ecosystems. QKD leverages the principles of quantum mechanics to enable unconditionally secure key exchange, immune to computational attacks. We propose an architecture where QKD-enabled edge gateways and IoT nodes facilitate real-time secure communication through quantum-secured channels. The study analyzes the feasibility of implementing QKD in resource-constrained IoT environments and evaluates its performance in terms of key generation rate, latency, and energy consumption. Simulation results demonstrate that the proposed QKD-IoT framework significantly outperforms conventional encryption protocols in resisting both classical and quantum-based attacks, making it a viable foundation for building post-quantum resilient IoT infrastructures. The research also outlines the challenges related to scalability, hardware integration, and key management, and proposes solutions through hybrid QKD-classical cryptography models. This work paves the way for a quantum-secure IoT future, ensuring trust, privacy, and integrity in hyper-connected digital ecosystems.
The rapid expansion of the Internet of Things (IoT) has introduced significant security challenges, especially in safeguarding sensitive data transmitted across vast networks. Traditional cryptographic methods, though widely used, face increasing vulnerabilities in light of advancements in quantum computing. This research explores the application of quantum cryptography, particularly Quantum Key Distribution (QKD), to secure data transmission in IoT networks. Quantum cryptography offers a revolutionary approach by utilizing the principles of quantum mechanics, ensuring communication channels are resistant to eavesdropping and quantum attacks. Despite its promise, integrating quantum cryptography into resource-constrained IoT environments presents several technical challenges. This paper examines current quantum cryptographic techniques, their feasibility for IoT applications, and proposed solutions for overcoming integration hurdles. Case studies of real-world implementations and experimental results are discussed to highlight the effectiveness of these methods. The findings suggest that quantum cryptography, while still in its infancy for IoT, has the potential to provide robust security solutions in future networks.
Due to the recent rapid growth of computing technologies, today's encrypted information based on classical computational complexities will soon no longer remain secure. Quantum cryptography, or quantum key distribution (QKD), relying on the physical laws of quantum mechanics, stands out as a more powerful cryptographic solution that enables the secret key to be shared securely over publicly unsecured communication channels in the presence of eavesdroppers. QKD can be possibly implemented over both optical fiber and free-space optical (FSO) links. Compared to optical fiber, FSO has the immediate advantage of flexibility and cost-effectiveness in terms of infrastructure deployment. More interestingly, recent advancements in satellite communications using FSO links promise the future of a global QKD network for highly secure applications. This paper reviews the development of QKD over FSO for both terrestrial and satellite channels, which highlights the most up-to-date QKD protocols. Owing to how the information is encoded, different QKD protocols are classified into technology-focused categories, where their properties are reviewed and compared. The feasibility of current QKD protocols is then investigated with respect to its specific application scenarios for terrestrial and satellite FSO links, equipped with results from both theoretical and experimental studies. Based on the latest free-space QKD achievements, novel perspectives for future developments and challenges to enhance the secrecy performance and reduce implementation cost are then summarized and comprehensively discussed. The potential combination of QKD and physical layer cryptography for the newly emerging wireless mobile communications networks involved with unmanned aerial vehicles (UAV) is also introduced.
Abstract Next-generation smart cities are increasingly reliant on high-speed, secure communication systems to support 6 G networks, IoT infrastructure, and autonomous systems. Classical cryptographic techniques are becoming vulnerable to quantum computing attacks, prompting the integration of quantum-secure communication mechanisms. In this context, Quantum Key Distribution (QKD) over Visible Light Communication (VLC) and Free Space Optical (FSO) networks offers a promising path toward ultra-secure, energy-efficient transmission. We propose an Entangled Photon Quantum Key Distribution (EP-QKD) framework that advances secure communication by integrating polarization-entangled photons, adaptive Quantum Bit Error Rate (QBER) optimization, and hybrid quantum-classical authentication anchored with blockchain. This advancement addresses critical limitations of traditional QKD systems—including high sensitivity to ambient interference, limited scalability, and high error rates—by employing entanglement-based noise resilience and real-time detection threshold control. Existing approaches to QoS and security—such as RSA-based encryption, BB84 and E91 protocols, and VLC-oriented modulation techniques—struggle with low secure key rates, high QBER under ambient light, and vulnerability to man-in-the-middle (MITM) attacks. EP-QKD overcomes these limitations by enhancing photon distribution fidelity, enabling decentralized authentication, and sustaining low error rates across dynamic urban optical environments. Experimental results demonstrate that EP-QKD achieves an average QBER of 1.2% and maintains QBER below 2.5% at 1000 lux, reducing errors by 40% over BB84 and 60% over E91. It attains secure key generation rates of over 1200 Mbps at 5 meters, outperforming BB84 and E91 by a significant margin. At 20 meters, EP-QKD maintains 300 Mbps, while BB84 drops to 40 Mbps. The MITM attack success rate is reduced to 0.01%, compared to 15% with BB84 + RSA. Additionally, EP-QKD achieves energy efficiency of 0.7 nJ/bit—nearly half of BB84’s requirement—making it suitable for energy-constrained IoT and mobile systems. Multi-user scalability testing confirms that EP-QKD can support up to 50 concurrent users with a key rate above 80 Mbps per user and QBER < 1.8%. A 3D analysis further shows that QBER remains below 5% even at 50 meters, demonstrating the framework’s robustness for long-distance secure optical communication. Overall, the proposed EP-QKD framework significantly enhances the performance, scalability, and resilience of quantum communication systems, making it a viable candidate for 6 G, IoT, and satellite-based secure infrastructure.