Quantum-Safe Blockchain: Mapping Research Fronts in Post-Quantum Cryptography, Quantum Threat Models, and QKD Integration

The Internet of Things (IoT) now underpins critical systems like healthcare monitors, smart home, smart grids, automotive V2V & V2X networks, and industrial controls but it still relies on classical cryptography, whose security assumptions are vulnerable to quantum computers. A large quantum computer could run Shor’s algorithm to break RSA/ECC and use Grover’s algorithm to accelerate brute-forcing of symmetric keys, undermining the confidentiality and authentication of data in these IoT applications. Researchers have proposed quantum cryptographic solutions. Quantum key distribution (QKD) and quantum random number generators (QRNGs) exploit quantum mechanics to detect eavesdropping and deliver provably secure key material. For example, chip-scale QRNGs can be embedded in IoT sensors to generate true random keys, boosting resistance to brute-force attacks. These quantum techniques provide information-theoretic secrecy, for instance, QKD-generated keys have been used to authenticate smart-grid SCADA. However, most IoT devices are resource-constrained, making direct deployment of conventional QKD hardware challenging. Post-quantum cryptography (PQC) complements quantum methods by providing algorithms such as lattice-based, hash-based that resist quantum attacks on existing hardware. Standardized PQC can be deployed via software updates on legacy IoT nodes, enabling scalable and quantum-safe security within current constraints. Researchers are exploring lightweight PQC for connected cars and e-health sensors. Hybrid approaches combining QKD/QRNG with PQC offer a layered defense. Since QKD protocols are regarded as ‘future-proof’ and PQC standards mature, their combined use will be essential for robust, quantum-safe IoT security. Miniaturizing quantum components such as integrated QKD/QRNG modules and optimizing lightweight PQC schemes for low-power IoT devices are future research directions to secure IoT networks.

In this section, I wish to put quantum key distribution (QKD) in the wider context of a cryptosystem. I shall discuss informally some aspects that are considered important. The questions I wish to answer here are: “What are the ingredients needed to make a QKD-based cryptosystem work? What services does it bring? What are its limitations?”

A roadmap from classical cryptography to post-quantum resistant cryptography for 5G-enabled IoT: Challenges, opportunities and solutions

Most currently used cryptographic tools for protecting data are based on certain computational assumptions, which makes them vulnerable with respect to technological and algorithmic developments, such as quantum computing. One existing option to counter this potential threat is quantum key distribution, whose security is based on the laws of quantum physics. Quantum key distribution is secure against unforeseen technological developments. A second approach is post-quantum cryptography, which is a set of cryptographic primitives that are believed to be secure even against attacks with both classical and quantum computing technologies. From this perspective, this study reviews recent progress in the deployment of the quantum-secured infrastructure based on quantum key distribution, post-quantum cryptography, and their combinations. Various directions in the further development of the full-stack quantum-secured infrastructure are also indicated. Distributed applications, such as blockchains and distributed ledgers, are also discussed.

Classical cryptographic systems are increasingly challenged by advances in computing power and new algorithmic techniques, particularly with the rise of quantum computing, which threatens the security of current encryption methods. This has spurred interest in quantum-resistant cryptography, aimed at creating algorithms that can withstand attacks from quantum computers. Traditionally, secure key transport over alternate channels has been a significant challenge, but quantum mechanics offers a solution. Quantum Key Distribution (QKD) is a revolutionary method for secure communication that leverages quantum principles. Unlike traditional methods, QKD provides unconditional security, with key security ensured by the laws of physics rather than computational difficulty. The BB84 protocol, introduced in 1984 by Bennett and Brassard, is a leading QKD scheme known for its simplicity and effectiveness in generating eavesdropping-resistant cryptographic keys. It facilitates secure key transport over alternate channels. This documentation aims to advance QKD security by practically implementing and analyzing the BB84 protocol. Through detailed theoretical analysis, simulation studies, and experimental validation, the practical impacts, and limitations of BB84-based QKD systems are examined. Additionally, a practical implementation of quantum key distribution using a sudoku key demonstrates the process's simplicity and effectiveness. These findings are expected to pave new paths in the field of cryptanalysis in the emerging Quantum Age.

ABSTARCT The rapid proliferation of smart home Internet of Things (IoT) technologies has transformed residential environments through intelligent automation, remote monitoring, and data driven decision making. Alongside these benefits, security risks have intensified due to advances in large scale quantum computing, which threaten the cryptographic foundations of current IoT systems. Widely deployed public key algorithms such as RSA and Elliptic Curve Cryptography are vulnerable to quantum attacks enabled by Shor’s algorithm, raising serious concerns regarding long term confidentiality, authentication, and trust in smart home ecosystems. To address this challenge, two major quantum resilient security paradigms have emerged: Post Quantum Cryptography (PQC) and Quantum Key Distribution (QKD). This paper presents a structured comparative study of PQC and QKD within smart home IoT environments, evaluating architectural compatibility, computational and energy constraints, scalability, deployment cost, communication models, and security guarantees. Realistic smart home scenarios including smart locks, surveillance cameras, and resource constrained sensor networks are examined to assess practical feasibility. The analysis demonstrates that while QKD offers information theoretic security under ideal conditions, its reliance on specialized quantum hardware and dedicated infrastructure makes it unsuitable for consumer smart homes. In contrast, PQC provides a scalable, software based, and cost effective approach that integrates seamlessly. Keywords: Post-Quantum Cryptography, Quantum Key Distribution, Smart Home IoT, Quantum Security, IoT Cryptography.

Quantum computing is an evolution of classical computing, capable of solving problems that are competitive enough to break the existing cryptographic primitives upon which current blockchain systems are based. Popular schemes like RSA, ECDSA, and SHA-256 can be compromised by quantum algorithms (Shor's and Grover's), raising questions about the security and trustworthiness of blockchain-based applications in finance, healthcare, and supply chains. Many current approaches focus on isolated aspects of the blockchain, such as cryptographic primitives or key exchange, without a comprehensive strategy that can guarantee end-to-end security in the face of a quantum threat. Finally, traditional consensus mechanisms such as Proof-of-Work and Proof-of-Stake are vulnerable to Sybil attacks, centralization, and leader-selection bias. When the adversary has access to a quantum computer, these issues become significantly worse. In this paper, we present QuantumShield-BC, a modular blockchain framework incorporating post-quantum cryptographic signatures, quantum key distribution (QKD), and a novel Quantum Byzantine Fault Tolerance (Q-BFT) consensus mechanism driven by quantum random number generation (QRNG) to address these challenges. QKD: The system supports tamper-proof key exchange, quantum-resilient consensus among validator nodes, and secure transaction signing. Experimental evaluation demonstrates that QuantumShield-BC achieves low consensus latency and high throughput, while providing perfect security against simulated attacks from Shor's and Grover's algorithms. The proposed framework eradicates the Sybil attack effectiveness up to 0%, eliminates replay and MITM vulnerabilities, and achieves an average throughput of over 7,000 transactions per second with 100 validators, orders of magnitude better than classical blockchain systems. The importance of each quantum part to the system's robustness is also demonstrated using an ablation study. With its unique ability to provide a post-quantum framework for high-assurance, general-purpose, scalable, and interoperable blockchain networks resistant to quantum-inspired attacks or quantum retrieval, QuantumShield-BC is practical for deployment in critical infrastructure and digital trust ecosystems where performance and a future-proof foundation are essential.

In the modern world, the financial sector faces a wide range of extraordinary events, from market shocks and geopolitical tensions to pandemics and cyberattacks. These diverse challenges significantly impact banks. Recently, particular attention has been drawn to the influence of artificial intelligence (AI) and quantum computing (QC) technologies on the stability of the financial system. This article analyzes the potential areas of impact of quantum technologies on the financial sphere in general and the resilience of financial institutions in particular.It's determined that quantum technologies can simultaneously pose both threats and new opportunities. Specifically, the article analyzes the potential of quantum technologies to break existing cryptographic algorithms that protect the confidential data of financial institutions' clients. This threat is exacerbated by the possibility of "harvest now, decrypt later" attacks, where malicious actors intercept data today with the intention of decrypting it in the future. This presents challenges and threats for online/mobile banking, payment operations, and corporate communications. Among the positive impacts of quantum technologies on banking, the article highlights improved financial risk assessment, particularly enhanced accuracy in stress testing, portfolio management, and derivatives pricing, by solving problems inaccessible to classical computing. The potential of quantum machine learning for fraud detection is also noted. Attention is given to the financial sector's response to these challenges. Initiatives for developing quantum-resistant (post-quantum) cryptography are considered as the primary method for mitigating the risks associated with the proliferation of quantum computing, along with new cryptographic protocols and quantum key distribution as a new opportunity to enhance security. The article emphasizes the responsibility of central banks in forming quantum-readiness strategies, including investments in post-quantum cryptography, expertise development, and the adaptation of regulatory frameworks. The conclusion drawn is that although the immediate benefits of quantum technologies may be modest, their long-term transformative potential for the financial sector is immense.

Emerging network applications are based on collaborative environments that rely on the secure group-based communication paradigm. These protocols use traditional public-key cryptography (PKC) for authenticating the group members and exchange secret keys. However, the foreseeable breakthrough of quantum computers represents a risk for the secure systems based on PKC. In order to prepare for such an event, quantum-secure group-based communications must be established. Post-quantumcryptography (PQC) and quantum-key distribution (QKD) are two quantum-resistant technologies that can be used for enabling the long term security in such collaborative environments. This work proposes four quantum-secure group-based communication solutions, based on contributory and decentralized protocols. PQC and hybrid technologies (PQC/QKD) are explored. The solutions use PQC Key-exchange algorithms or QKD protocols (decoy-BB84 and T12) for key generation and PQC signature algorithms for authentication. For the first time hybrid schemes for group-based technologies are designed and explored. Results show that the group-based decentralized protocol (PQC SLIMCAST) outperforms the contributory protocol PQC GAKE. The PQC-based approaches have a better performance than the QKD versions.

Security of data transported in telecommunication networks is of primary importance for internet service providers (ISP) as data safety is at the basis of the mutual trust with customers. People were looking for theoretically secure transmission techniques since a long-time to ensure long-term confidentiality of data flows exchanged on these networks. Besides advanced encryption algorithms and the recently proposed post-quantum cryptography (PQC), a physics-based technology using quantum key distribution (QKD) was proposed a long time ago to approach this objective. QKD recently gained a renewed interest with many research programs worldwide supported by public authorities, and some pre-industrial QKD systems delivered to the market. However, some constraints of optical transport networks make sometimes complicated the deployment of such QKD systems in the field, such as the need of a dedicated fiber infrastructure for QKD, or the impossibility for a quantum key to pass through an optical amplifier. In this paper, we report the transmission of a coherent 400-Gbps dual-polarization 16QAM channel that transports QKD-secured 100-GbEthernet data stream with other fifty-four WDM channels at 100-Gbps over 184-km of standard single mode fiber (SSMF) through three QKD links (of 66-km, 50-km and 66-km, respectively) and two trusted nodes. On the two longest sections of the link, the quantum key and WDM signals are propagated on two different fibers, while on the shortest section of 50-km the QKD signal and WDM comb co-propagate on a same fiber. Secret key rates (SKR) and quantum bit error rate (QBER) are measured and reported on each of the three fiber sections. Various analyses are carried out on the co-propagation section of 50-km: the SKR / QBER sensitivity to the optical power of the WDM comb, or to the optical signal-to-noise ratio (OSNR) of the WDM channels co-propagating with the quantum signal is studied. The unique arrangement of the most advanced QKD and WDM technologies reported here constitutes, in our opinion, a world first, and demonstrates that QKD and WDM solutions can coexist in already deployed optical transport networks.

There has been a dramatic increase in the number of Internet of Things (IoT) devices and their applications. Furthermore, there is a growing impetus to integrate IoT networks on a global scale, using satellites to expand the range of IoT connectivity into geographically remote areas. Ensuring the security of satellite backhaul for IoT networks is thus of paramount importance. The steady advance of quantum computing in recent years threatens to nullify classical cryptographic approaches based on assumptions of computational hardness, motivating the need for post-quantum cryptography. Quantum computing algorithms have been developed that, once a quantum computer of sufficient scale is realised, will be able to break classical cryptosystems efficiently (at polynomial-time complexity). A promising method of securing information against this threat at the physical layer has emerged in the form of quantum key distribution (QKD). QKD exploits the fundamental physical properties of light to guarantee information-theoretic security. Research into the application and standardisation of QKD to secure satellite backhaul, however, is still in its infancy. This paper presents a brief overview of the theoretical basis for QKD, whilst also providing a survey of contemporary QKD protocols. It evaluates the ability of these protocols to secure satellite backhaul in the context of a typical satellite-IoT network architecture. Furthermore, it highlights the vulnerabilities, as well as the technical challenges associated with this endeavour. Finally, it proposes directions for future research and development into protocols and standardisation for the satellite-integrated IoT domain. Several challenges must be overcome before QKD can evolve into a global-scale solution for securing satellite-IoT. Secret key generation rate remains very low in practical demonstrations of trusted-relay QKD satellite architectures. Further research is needed to overcome or mitigate the fundamental rate-distance trade-off before satellite QKD can be considered practicable in an IoT application. Alternatives that do not rely on trusted nodes are contingent on nascent technologies such as quantum repeaters and quantum memory. Whilst in theory QKD provides perfect information-theoretic security, it remains vulnerable to attacks that exploit imperfections in real-world equipment. Further effort is needed to develop QKD protocols that can safeguard against the aforementioned challenges.

The security of quantum cryptography relies on the foundations of quantum mechanics, in contrast to traditional public key cryptography which relies on the computational difficulty of certain mathematical functions, and cannot provide any indication of eavesdropping or guarantee of key security. The proposal present in this work develops a quantum key distribution model to safeguard security in large networks, in the directions of classical cryptography and quantum cryptography. Two three-party Quantum key distribution are used in this model, one with implicit user authentication and the other with explicit mutual authentication, are proposed to demonstrate the merits of the new combination. The performance of Quantum Key Distribution (QKD) systems have notably progressed since the early experimental demonstrations. The current evolutions in QKD research indicate that the pace of this progression is very likely to be maintained, if not increased, in the future years. In parallel to these improvements of QKD techniques, commercial products are also being developed, making QKD deployment a feasible alternative for securing real data networks. Deployment of a real QKD network is however far from being straightforward. It requires development of a network architecture connecting multiple users that may possibly be very far away from each other. Considering the fact that the existing QKD links are only point-to-point, and intrinsically limited in distance, deployment of a practical QKD network structure is a nontrivial problem. The proposed work describes the proposed architecture for a QKD network specify the requirements relevant to the network design, protocols, and services. The objective of this specification is to define the major components and their main features The proposal provides security against such attacks as man-in-the-middle, eavesdropping and replay. It also improves the efficiency of the quantum key distribution which contains the fewest number of communication rounds among existing Quantum key distributions. In this model two parties can share and use a long-term secret (repeatedly). To prove the security of the proposed schemes, this proposed model provides a primitive called the Unbiased-Chosen Basis (UCB) assumption with the quantum key in angular positions.

The book provides a study of quantum computing effects on contemporary cryptographic systems. This research examines quantum threats and the requirement for post-quantum computations which lead to a study of developing post-quantum cryptographic methods while exploring fundamental quantum concepts that show the menace classical cryptography faces. RSA and elliptic curve cryptography (ECC) demonstrate weakpoints that create an immediate need for moving toward quantum-resistant system architectures . Quantum attacks generate important risks which demand organizations to implement secure cryptographic measures. The text gives insight into hash-based cryptographic algorithms parallel to lattice-based and code-based and isogeny-based algorithms. The book investigates quantum-resistant hash functions together with NIST’s post-quantum cryptography initiative and quantum-safe public key encryption and Quantum Key Distribution (QKD) and hybrid cryptographic methods. The book evaluates digital signatures as cybersecurity anchors through NIST’s post-quantum signature models and specific algorithms. The paper evaluates operational barriers that face post-quantum cryptography adoption through investigations about key migration together with a review of interoperability needs and explanations about protected key systems. The book explores emerging quantum computing technology through investigations about quantum-proof digital currencies along with QML security risks. The book analyzes ethical guidelines which prioritize security and privacy against worldwide accessibility and verify government participation in post-quantum cryptography implementation. This document presents both a planned path toward quantum-security readiness together with scheduling plans and scientific monitoring methodologies that protect networks from quantum age security hazards.

Cryptographic algorithms are crucial for secure communication in the Internet of Things (IoT). Quantum computers threaten public key cryptography algorithms like RSA (Rivest, Shamir, Adleman) and Diffie-Hellman (DH) key exchange schemes, which are widely in use today. As cryptographic algorithms are the foundation of secure internet communication, the development of Quantum Key Distribution (QKD) and Post-Quantum Cryptography (PQC) is essential to protect transactions over the internet. However, solutions like Quantum Key Distribution require heavy infrastructure. So, it is not feasible for the Internet of Things with fewer resources in computing power and form factor. Post-Quantum Cryptography is helpful on these devices. But, it needs further developments and improvements. This paper analyzes cryptography algorithms and protocols of IoT with different categories. Integrated PQC of National Institute of Standards and Technology (NIST) third level finalists on Raspberry Pi 4 (RPI4) board with Linux operating system. The performance of Post-Quantum Cryptography schemes for IoT has been evaluated. Finally, a Post-Quantum Cryptography scheme has been suggested for the Internet of Things based on the performance analysis.

The Internet has become an increasingly appealing medium for telecare medicine information systems (TMISs). However, the open nature of the Internet poses serious security threats and vulnerabilities to TMISs and privacy concerns to the patients and medical personnel. This work proposes a hybrid quantum key distribution protocol to provide security in TMISs, leveraging the key agreement of classical and quantum key distribution. Our protocol induces low energy and computation overheads to achieve privacy and trusted operations for TMISs. This is because quantum key distribution employs the principles of quantum mechanics rather than computational complexity, to avoid various attacks such as the man-in-the-middle attacks, the replay attacks and the passive attacks. Meanwhile, classical cryptography can be used to achieve user authentication efficiently. Therefore, our protocol may be available with the rapid developments of extensive experiments for quantum key distribution.