Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2607.01989

Insecurity of Measurement-Device-Independent Quantum Key Distribution

Konstantin Zaitsev, Polina Acheva

quant-phSubmitted Jul 2, 2026• Announced Jul 3, 2026• 0 citations• Revised Jul 4, 2026 (v2)
v1 · Jul 2, 2026v2 · Jul 4, 2026
arXivHTMLPDF

Abstract

The security of practical quantum key distribution (QKD) systems is fundamentally constrained by vulnerabilities of single-photon detectors. Measurement-device-independent quantum key distribution (MDI-QKD) was proposed to remove this limitation by allowing all measurements to be performed by a completely untrusted party, under the assumption that the measurement node can be treated as adversarial but does not compromise the security guarantees of the protocol. Here we show that this assumption is insufficient under realistic adversarial control of the measurement device. We present an attack in which an adversary exploits active control of the measurement node (Charlie) to obtain significant information about the secret key. The attack enables recovery of up to 70\% of the sifted key while introducing only 5.6\% quantum bit error rate. Unlike previously reported attacks targeting specific implementations of MDI-QKD, our results demonstrate a limitation of the standard security model underlying the protocol. These findings indicate that additional constraints on the measurement-device independence assumption, or refined security analyses incorporating stronger adversarial capabilities, are required to ensure the security of MDI-QKD in realistic scenarios.

Related papers

DGL22: A practical Quantum key distribution

Mohammed Aldarwbi, Ali Akbar Ghorbani, Arash Habibi Lashkari

Abstract Quantum key distribution (QKD) protocols are unconditionally secure, providing that quantum devices are truthful. Device-independent quantum key distribution (DI-QKD) protocols offer the prospect of distributing secret keys with minimal assumptions. The DI-QKD protocols are hard to implement using the current technologies as they require all the quantum devices to be uncharacterized. Measurement device independent quantum key distribution (MDI-QKD) protocols assume that the measurement devices are not truthful; the adversary might make them. MDI-QKD is secure but more challenging to implement. Receiver-device-independent quantum key distribution (RDI-QKD) protocols assume that the receiver's measurement devices can be viewed as a black box while the sender's device can be trusted. RDI-QKD relies on reasonable assumptions that make it easy to implement using the current state-of-the-art technology. We propose an RDI-QKD protocol, called DGL22. DGL22 is secure against all known attacks that are allowed by quantum mechanics. DGL22 provides several benefits over previous protocols, including the capability to attain high communication and sifting efficiency.

•Oct 25, 2022•0 citations

Fully passive measurement-device-independent quantum key distribution

Jinjie Li, Wenyuan Wang, Hoi‐Kwong Lo

A recently proposed fully passive quantum key distribution (QKD) removes all source modulator side channels. In this work, we combine fully passive sources with measurement-device-independent (MDI) QKD to simultaneously remove side channels from source modulators and detectors. We show a numerical simulation of passive MDI QKD, and we obtain an acceptable key rate while achieving much better implementation security, as well as ease of implementation, compared with a recently proposed fully passive twin-field QKD, paving the way towards more secure and practical QKD systems. We prove that a fully passive protocol is compatible with MDI QKD and we propose a novel idea that can improve the sifting efficiency.

arXiv:2309.07673•Physical Review Applied•Jun 25, 2024•10 citations

High-secure quantum communication and networks

Guan‐Jie Fan‐Yuan

Quantum key distribution (QKD) can serve large numbers of users with unconditional secure communication, in which measurement-device-independent (MDI) QKD protocol can conveniently enhance realistic security by eliminating all detector side channels. In multi-user scenarios, MDI-QKD networks should meet the requirements of reliability and robustness. Around the issues, we complete a series of work on performance improvement, low-cost deployment, and robust networking. First is to answer how to change the trusted node to the untrusted node with low cost, here we propose and demonstrate an MDIQKD which is compatible with phase encoding BB84 networks, allowing for economical deployment of MDI-QKD networks and reconciliation between high key rate and high realistic security in the same network. Then we make the MDI networks more robust. We design an MDI-QKD networking scheme for multi-user access where more than two users can generate keys synchronously regardless of aligning reference frames and compensating channel disturbance on polarization. Third, we find a general method to distil secure keys from quantum discord, which is different to the previous entanglement-based frameworks of MDI-QKD, allowing imperfect preparation and measurement of quantum states. The series of work can help the practical application of MDI-QKD networks, and promote the development of quantum networks.

Opto-Electronics and Communications Conference (OECC)•Jun 30, 2024•0 citations

Measurement‐Device‐Independent Quantum Key Distribution With Third‐Party Quantum Sources

Xinting Su, Xiangfu Zou, Xin Wang +5 more

ABSTRACT Traditional quantum key distribution (QKD) protocols secure communications by trusting the source or the measurement device. Among these, measurement‐device‐independent quantum key distribution (MDI‐QKD) protocols remove the need to trust the measurement device by delegating it to an untrusted third party. We categorize the operations of the QKD protocol into three fundamental processes: realizing quantum sources, applying unitary operations, and performing measurements. Furthermore, we have designed an MDI‐QKD protocol utilizing third‐party quantum sources, which establishes connections with the BB84 protocol, the BBM92 protocol, and the first MDI‐QKD protocol. Specifically, the three protocols can be regarded as special cases of the proposed protocol under different equivalent implementations. Under the assumptions of the source's dimension and ideal operation devices, the proposed protocol can guarantee information‐theoretic security even if the quantum sources and measurement devices are controlled by an adversary. Moreover, we demonstrate that its security is equivalent to that of the BBM92 protocol, with a tolerable error rate of approximately . Finally, we give a generalization of the proposed protocol and a corresponding experimental setup framework. This work reveals certain inherent connections between different quantum key distribution protocols, enriching the research results of quantum key distribution.

Annalen der Physik•Aug 1, 2026•0 citations

Security of quantum key distribution with realistic sources

Xoel Sixto

Quantum Key Distribution (QKD) offers information-theoretic security grounded in the laws of quantum mechanics rather than computational assumptions. While its theoretical foundations are robust, practical implementations necessarily deviate from the idealized models assumed in security analyses, opening the door to side-channel attacks and implementation loopholes. In particular, most research to date has focused on mitigating vulnerabilities in the measurement devices, leading to the development of Measurement-Device-Independent QKD (MDI-QKD) and Twin-Field QKD (TF-QKD), which effectively close all receiver-side loopholes. By contrast, the security of the source has remained less explored, despite being critical for the overall integrity of QKD systems. The goal of this thesis is to develop security proofs that explicitly account for realistic imperfections in QKD sources. Special emphasis is placed on three main aspects: correlations between emitted pulses that violate independence assumptions, imperfect phase randomization arising from practical modulation schemes, and leakage of internal settings through passive or active side channels. By formulating rigorous methods to analyze these imperfections, the work aims to provide a framework that enables practitioners to quantify and mitigate implementation risks systematically. Additionally, this thesis seeks to clarify under which conditions the commonly used decoy-state method remains secure, and to what extent source assumptions can be relaxed without compromising performance. This thesis aims to advance the understanding of how real-world deviations impact QKD security and to contribute to the development of protocols and devices. Ultimately, this work is motivated by the ambition to help bring QKD from a theoretically promising idea to a mature technology deployable with confidence in practical scenarios.

•Nov 7, 2025•0 citations

Intensity correlations in measurement-device-independent quantum key distribution

Junxuan Liu, Tianyi Xing, Ruiyin Liu +3 more

The intensity correlations due to imperfect modulation during the quantum-state preparation in a measurement-device-independent quantum key distribution (MDI QKD) system compromise its security performance. Therefore, it is crucial to assess the impact of intensity correlations on the practical security of MDI QKD systems. In this work, we propose a theoretical model that quantitatively analyzes the secure key rate of MDI QKD systems under intensity correlations. Furthermore, we apply the theoretical model to a practical MDI QKD system with measured intensity correlations, which shows that the system struggles to generate keys efficiently under this model. We also explore the boundary conditions of intensity correlations to generate secret keys. This study extends the security analysis of intensity correlations to MDI QKD protocols, providing a methodology to evaluate the practical security of MDI QKD systems.

arXiv:2408.08011•Optics Express•Sep 30, 2024•1 citation
The security of practical quantum key distribution (QKD) systems is fundamentally constrained by vulnerabilities of single-photon detectors. Measurement-device-independent quantum key distribution (MDI-QKD) was proposed to remove this limitation by allowing all measurements to be performed by a completely untrusted party, under the assumption that the measurement node can be treated as adversarial but does not compromise the security guarantees of the protocol.
Here we show that this assumption is insufficient under realistic adversarial control of the measurement device. We present an attack in which an adversary exploits active control of the measurement node (Charlie) to obtain significant information about the secret key. The attack enables recovery of up to 70% of the sifted key while introducing only 5.6% quantum bit error rate. Unlike previously reported attacks targeting specific implementations of MDI-QKD, our results demonstrate a limitation of the standard security model underlying the protocol.
These findings indicate that additional constraints on the measurement-device independence assumption, or refined security analyses incorporating stronger adversarial capabilities, are required to ensure the security of MDI-QKD in realistic scenarios.
Abstract Quantum key distribution (QKD) protocols are unconditionally secure, providing that quantum devices are truthful. Device-independent quantum key distribution (DI-QKD) protocols offer the prospect of distributing secret keys with minimal assumptions. The DI-QKD protocols are hard to implement using the current technologies as they require all the quantum devices to be uncharacterized. Measurement device independent quantum key distribution (MDI-QKD) protocols assume that the measurement devices are not truthful; the adversary might make them. MDI-QKD is secure but more challenging to implement. Receiver-device-independent quantum key distribution (RDI-QKD) protocols assume that the receiver's measurement devices can be viewed as a black box while the sender's device can be trusted. RDI-QKD relies on reasonable assumptions that make it easy to implement using the current state-of-the-art technology. We propose an RDI-QKD protocol, called DGL22. DGL22 is secure against all known attacks that are allowed by quantum mechanics. DGL22 provides several benefits over previous protocols, including the capability to attain high communication and sifting efficiency.
A recently proposed fully passive quantum key distribution (QKD) removes all source modulator side channels. In this work, we combine fully passive sources with measurement-device-independent (MDI) QKD to simultaneously remove side channels from source modulators and detectors. We show a numerical simulation of passive MDI QKD, and we obtain an acceptable key rate while achieving much better implementation security, as well as ease of implementation, compared with a recently proposed fully passive twin-field QKD, paving the way towards more secure and practical QKD systems. We prove that a fully passive protocol is compatible with MDI QKD and we propose a novel idea that can improve the sifting efficiency.
Quantum key distribution (QKD) can serve large numbers of users with unconditional secure communication, in which measurement-device-independent (MDI) QKD protocol can conveniently enhance realistic security by eliminating all detector side channels. In multi-user scenarios, MDI-QKD networks should meet the requirements of reliability and robustness. Around the issues, we complete a series of work on performance improvement, low-cost deployment, and robust networking. First is to answer how to change the trusted node to the untrusted node with low cost, here we propose and demonstrate an MDIQKD which is compatible with phase encoding BB84 networks, allowing for economical deployment of MDI-QKD networks and reconciliation between high key rate and high realistic security in the same network. Then we make the MDI networks more robust. We design an MDI-QKD networking scheme for multi-user access where more than two users can generate keys synchronously regardless of aligning reference frames and compensating channel disturbance on polarization. Third, we find a general method to distil secure keys from quantum discord, which is different to the previous entanglement-based frameworks of MDI-QKD, allowing imperfect preparation and measurement of quantum states. The series of work can help the practical application of MDI-QKD networks, and promote the development of quantum networks.
ABSTRACT Traditional quantum key distribution (QKD) protocols secure communications by trusting the source or the measurement device. Among these, measurement‐device‐independent quantum key distribution (MDI‐QKD) protocols remove the need to trust the measurement device by delegating it to an untrusted third party. We categorize the operations of the QKD protocol into three fundamental processes: realizing quantum sources, applying unitary operations, and performing measurements. Furthermore, we have designed an MDI‐QKD protocol utilizing third‐party quantum sources, which establishes connections with the BB84 protocol, the BBM92 protocol, and the first MDI‐QKD protocol. Specifically, the three protocols can be regarded as special cases of the proposed protocol under different equivalent implementations. Under the assumptions of the source's dimension and ideal operation devices, the proposed protocol can guarantee information‐theoretic security even if the quantum sources and measurement devices are controlled by an adversary. Moreover, we demonstrate that its security is equivalent to that of the BBM92 protocol, with a tolerable error rate of approximately . Finally, we give a generalization of the proposed protocol and a corresponding experimental setup framework. This work reveals certain inherent connections between different quantum key distribution protocols, enriching the research results of quantum key distribution.
Quantum Key Distribution (QKD) offers information-theoretic security grounded in the laws of quantum mechanics rather than computational assumptions. While its theoretical foundations are robust, practical implementations necessarily deviate from the idealized models assumed in security analyses, opening the door to side-channel attacks and implementation loopholes. In particular, most research to date has focused on mitigating vulnerabilities in the measurement devices, leading to the development of Measurement-Device-Independent QKD (MDI-QKD) and Twin-Field QKD (TF-QKD), which effectively close all receiver-side loopholes. By contrast, the security of the source has remained less explored, despite being critical for the overall integrity of QKD systems. The goal of this thesis is to develop security proofs that explicitly account for realistic imperfections in QKD sources. Special emphasis is placed on three main aspects: correlations between emitted pulses that violate independence assumptions, imperfect phase randomization arising from practical modulation schemes, and leakage of internal settings through passive or active side channels. By formulating rigorous methods to analyze these imperfections, the work aims to provide a framework that enables practitioners to quantify and mitigate implementation risks systematically. Additionally, this thesis seeks to clarify under which conditions the commonly used decoy-state method remains secure, and to what extent source assumptions can be relaxed without compromising performance. This thesis aims to advance the understanding of how real-world deviations impact QKD security and to contribute to the development of protocols and devices. Ultimately, this work is motivated by the ambition to help bring QKD from a theoretically promising idea to a mature technology deployable with confidence in practical scenarios.
The intensity correlations due to imperfect modulation during the quantum-state preparation in a measurement-device-independent quantum key distribution (MDI QKD) system compromise its security performance. Therefore, it is crucial to assess the impact of intensity correlations on the practical security of MDI QKD systems. In this work, we propose a theoretical model that quantitatively analyzes the secure key rate of MDI QKD systems under intensity correlations. Furthermore, we apply the theoretical model to a practical MDI QKD system with measured intensity correlations, which shows that the system struggles to generate keys efficiently under this model. We also explore the boundary conditions of intensity correlations to generate secret keys. This study extends the security analysis of intensity correlations to MDI QKD protocols, providing a methodology to evaluate the practical security of MDI QKD systems.