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IEEE International Conference on Quantum Artificial Intelligence (QAI)

Design of a Realistic Device-Independent QKD System

Ugo Chirico, Salvatore Cuomo, Miriam Del Latte, Gianluca Vallini

Published Nov 2, 2025• 0 citations
Publisher

Abstract

Device-Independent Quantum Key Distribution (DI-QKD) represents the pinnacle of secure quantum communication, offering cryptographic guarantees that are independent of the trustworthiness of the devices used. Unlike traditional QKD schemes that rely on specific assumptions about internal device behaviour, DI-QKD leverages the violation of Bell inequalities to certify security solely from observed statistics. This approach eliminates a wide range of side-channel and implementation attacks, making it especially attractive for critical infrastructures and defense applications. The core concept hinges on the ability of the communicating parties, traditionally named Alice and Bob, to generate shared secret keys through the violation of Bell inequalities verified at a central node, named Charlie, regardless of hardware imperfections. Previous works demonstrated the feasibility of a Bell-certified key exchange over a real optical channel using a heralded entanglement scheme. This work aims to build on that foundation, presenting a full-stack engineering implementation of a DI-QKD system that includes industrial-grade entangled photon sources, high-efficiency SNSPD detectors, central-node heralding logic, and a real-time software stack for key management, observability, and integration with classical IT infrastructure.

DOI
10.1109/qai63978.2025.00034

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Device-Independent Quantum Key Distribution (DI-QKD) represents the pinnacle of secure quantum communication, offering cryptographic guarantees that are independent of the trustworthiness of the devices used. Unlike traditional QKD schemes that rely on specific assumptions about internal device behaviour, DI-QKD leverages the violation of Bell inequalities to certify security solely from observed statistics. This approach eliminates a wide range of side-channel and implementation attacks, making it especially attractive for critical infrastructures and defense applications. The core concept hinges on the ability of the communicating parties, traditionally named Alice and Bob, to generate shared secret keys through the violation of Bell inequalities verified at a central node, named Charlie, regardless of hardware imperfections. Previous works demonstrated the feasibility of a Bell-certified key exchange over a real optical channel using a heralded entanglement scheme. This work aims to build on that foundation, presenting a full-stack engineering implementation of a DI-QKD system that includes industrial-grade entangled photon sources, high-efficiency SNSPD detectors, central-node heralding logic, and a real-time software stack for key management, observability, and integration with classical IT infrastructure.
This paper explores the design and theoretical foundations of quantum key distribution (QKD) protocols engineered for device-independent security. The core argument presented is that achieving unconditional security in QKD is possible without relying on the assumption of perfect hardware, a limitation inherent in many existing protocols. We propose a framework leveraging Bell inequality violations to establish secure key exchange, offering a fundamentally different approach compared to traditional protocols. This approach aims to mitigate the risks associated with side-channel attacks and device imperfections. The protocol outlined here represents a significant step towards realizing truly robust and secure quantum communication systems, offering a pathway for building cryptographic infrastructure resilient to evolving threats. The key contributions lie in the theoretical rigor applied to device independence and the utilization of Bell tests as a core mechanism for establishing security. The presented model offers a starting point for future research and development in this critical area of quantum cryptography.
Device-independent quantum key distribution (DI-QKD) enables information-theoretically secure key exchange between remote parties without any assumptions on the internal workings of the devices used for its implementation. However, its practical deployment remains severely constrained by the need for loophole-free Bell inequality violations, which are highly susceptible to losses and detection efficiencies. In this paper, we propose two long-distance DI-QKD protocols based on a heralding scheme using single-photon interference. Our protocols consist of only standard quantum optics tools such as two-mode squeezed states, displacement operations, and on-off detectors, making them experimentally accessible. To further enhance robustness against realistic imperfections, we integrate a classical noisy preprocessing technique during post-processing. We calculate key rates of the protocols by numerical optimization and show the supremacy of this implementation over existing protocols in terms of communication distances.
This study provides an integrated quantum classical and traditional cryptographic framework that combines the Device-Independent Quantum Key Distribution to RSA and AES for achieving highly enhanced secure communication. Upgrading the previous work, involving a BB84 with RSA and AES hybrid scheme. Similarly, this paper advances the security by incorporating DI-QKD in which it rejects assumptions about the internal functioning of the quantum devices and protects against the side channel attacks. In this proposed model, DI-QKD helps to create or generate provably secure shared keys, based on Bell-inequality violations whereas RSA ensures reliability in authentication and public key exchange. AES provides high-speed symmetric encryption for the mass data protection. This paper therefore establishes the complete DI-QKD with RSA and AES workflow simulating secure key generation; producing encrypted message outputs and the performance metrics such as key generation rate; quantum bit error rate; encryption time and overall system throughput is measured. These graphical results are compared with the earlier BB84 hybrid model to evaluate operational efficiency, resistance to adversarial interference and security robustness and too highlights the quantitative improvement offered by DI-QKD especially in antagonistic or untrusted device scenarios. Hence this paper demonstrates that the DI-QKD with RSA, AES hybrid system offering strengthened quantum safe security with classical compatibility, positioning it as a propitious architecture for the futuristic cryptographic networks.
Abstract Device-independent quantum key distribution (DIQKD) enables the generation of secret keys over an untrusted channel using uncharacterized and potentially untrusted devices 1–9 . The proper and secure functioning of the devices can be certified by a statistical test using a Bell inequality 10–12 . This test originates from the foundations of quantum physics and also ensures robustness against implementation loopholes 13 , thereby leaving only the integrity of the users’ locations to be guaranteed by other means. The realization of DIQKD, however, is extremely challenging—mainly because it is difficult to establish high-quality entangled states between two remote locations with high detection efficiency. Here we present an experimental system that enables for DIQKD between two distant users. The experiment is based on the generation and analysis of event-ready entanglement between two independently trapped single rubidium atoms located in buildings 400 metre apart 14 . By achieving an entanglement fidelity of F ≥0.892(23) {\mathcal F} \,\ge 0.892(23)F≥0.892(23) ℱ ≥ 0.892 ( 23 ) and implementing a DIQKD protocol with random key basis 15 , we observe a significant violation of a Bell inequality of S = 2.578(75)—above the classical limit of 2—and a quantum bit error rate of only 0.078(9). For the protocol, this results in a secret key rate of 0.07 bits per entanglement generation event in the asymptotic limit, and thus demonstrates the system’s capability to generate secret keys. Our results of secure key exchange with potentially untrusted devices pave the way to the ultimate form of quantum secure communications in future quantum networks.
ABSTRACT Quantum key distribution (QKD) is based on the laws of quantum mechanics to enable provably secure communication. Despite its theoretical security promise, practical QKD systems are vulnerable to serious attacks, including side‐channel attacks and detector loopholes, and assumes a trusted device characterisation. Device‐independent quantum key distribution (DIQKD) overcomes these limitations by relying solely on observed nonlocal correlations, certified through Bell inequality violations, thereby removing assumptions about the internal workings of the measurement devices. In this paper, we first review the foundational principles underlying DIQKD, including Bell tests and security definitions. We then examine a range of protocol designs, including CHSH‐based schemes, and non‐local game frameworks, alongside with their security proofs. We also assess recent experimental implementations and discuss source architectures, detection technologies and finite‐key analyses. Finally, we identify current open problems, such as noise tolerance, generation rates and integration with quantum networks and outline promising directions for future research to realize robust high‐performance DIQKD.
The rapid advancement of quantum computing threatens to undercut the mathematical foundations of today’s public-key cryptosystems. Quantum key distribution (QKD) provides an information-theoretically secure substitute whose security is derived from physical laws rather than computational complexity. However, most practical QKD systems still rely on trusted hardware components that are vulnerable to manufacturing backdoors, misalignment, and side-channel leakage. Device-Independent Quantum Key Distribution (DIQKD) removes these assumptions by certifying security from experimentally observed Bell-inequality violations, treating devices as untrusted black boxes.This paper provides a complete overview of DIQKD research, focusing on the evolution from early theoretical security proofs to real-world demonstrations on quantum hardware. We review implementation issues on platforms like IBM Quantum, evaluate finite-key security models, and study fundamental protocols. Building on this review, the Quantum Guard framework is presented as a conceptual design that combines adaptive optimization, finite-key estimation, and active attack detection to achieve resilient, device-independent communication. We further demonstrate practical file encryption using DIQKD-generated keys. Finally, we discuss current limitations and strategic objectives for building scalable, commercial quantum-secure networks.