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:2211.13669 · Lobachevskii Journal of Mathematics

Joint Eavesdropping on the BB84 Decoy State Protocol with an Arbitrary Passive Light-source Side Channel

Бабухин Данила Валерьевич, Сыч Денис Васильевич

Published Jun 1, 2024• 2 citations
arXivHTMLPDF

Abstract

Abstract Passive light-source side channel in quantum key distribution (QKD) provides additional information to an eavesdropper via various non-operational degrees of freedom of the optical signal. The currently known explicit eavesdropping strategies aimed at additional information gain from the passive light-source side channel were limited to the attack on the side channel and the operational degree of freedom separately. As a result, their efficiency is far from being optimal. Here we provide the joint eavesdropping strategy on both operational degree of freedom and the passive light-source side channel of the generic form, and develop a method to calculate the corresponding secret key rate. In particular, we use the optimal phase-covariant cloning of the signal photon state followed by a joint collective measurement of the side channel and the operational degree of freedom. To estimate security under the explicit attack strategy, we develop an ‘‘effective error’’ method and demonstrate it on the BB84 protocol with decoy states. Our work extends the practical analysis of QKD protocols with the light-source side channels and can be used as a tool for the analysis of realistic eavesdropping methods.

DOI
10.1134/s1995080224602753

Related papers

Explicit attacks on passive side channels of the light source in the BB84 decoy state protocol

Бабухин Данила Валерьевич, Сыч Денис Васильевич

Abstract Various imperfections of the hardware in quantum key distribution (QKD) lead to discrepancies between the theory and real-world devices. An eavesdropper can use these discrepancies to compromise the QKD security, thus legitimate sides need to estimate the influence of imperfections to prevent the loss of security. Here we investigate explicit eavesdropping attacks on passive side channels of the light source for a BB84 decoy states QKD protocol. We consider an optimal phase-covariant cloning attack, followed by unambiguous state discrimination and a joint measurement. Our calculations provide a hint that for state-of-the-art light sources the inherent presence of passive side channels still allows the protocol to be secure, albeit with the reduced secret key rates.

Journal of Physics Conference Series•Jul 1, 2021•4 citations

Unambiguous state discrimination and joint measurement attacks on passive side channel of the light source in BB84 decoy-state protocol

Бабухин Данила Валерьевич, Сыч Денис Васильевич

Abstract Quantum key distribution (QKD) has a promise of unconditionally secure communication between the remote sides. The real-world QKD implementations, however, have numerous loopholes, both of engeneering and physical origin, and compromise the security promise. In this work, we investigate two attack strategies on the passive side channel of the light source along with the optimal cloning attack on the BB84 protocol with decoy-states. We calculate an upper bound of a secret key rate for these situations and show that the joint measurement attack on the signal and side channel degree of freedom is more effective to the adversary.

Journal of Physics Conference Series•Dec 1, 2021•2 citations

Explicit attacks on the Bennett-Brassard 1984 protocol with partially distinguishable photons

Бабухин Данила Валерьевич, Dmitry Anatolevich Kronberg, Сыч Денис Васильевич

The distinguishability of photons in nonoperational degrees of freedom compromises the unconditional security of quantum key distribution since an eavesdropper can improve attack strategies by exploiting this distinguishability. However, the optimal eavesdropping strategies in the presence of light-source side channels are not known. Here we provide several explicit attack strategies on the Bennett-Brassard 1984 (BB84) protocol with partially distinguishable photons. In particular, we consider the phase-covariant cloning attack, which is optimal in the absence of side channels, and show that there are even better strategies in the presence of side channels. The improved strategies exploit a measurement of the side-channel state followed by an attack on the signal photon. Our results explicitly demonstrate a reduction of the critical error rate and set an upper bound on the practical secret key rate.

arXiv:2205.15964•Physical Review A•Oct 3, 2022•8 citations

Intercept-resend attack on passive side channel of the light source in BB84 decoy-state protocol

Бабухин Данила Валерьевич, Сыч Денис Васильевич

Abstract Quantum key distribution (QKD) promises unconditionally secure communication based on fundamental laws of physics, though practical realizations of QKD may have loopholes and side channels, thus their security can be compromised. We analyze the intercept-resend attack on the BB84 decoy-state protocol under the presence of a passive side channel of the light source. We derive an upper bound for the secret key rate and show that it does not significantly deviate from the ideal side-channel-free case.

Journal of Physics Conference Series•Dec 1, 2020•3 citations

Bounding light source side channels in QKD via Hong-Ou-Mandel interference

Alexander Duplinskiy, Сыч Денис Васильевич

Side-channel attacks on practical quantum key distribution systems compromise its security. Although some of these attacks can be taken into account, the general recipe of how to eliminate all side-channel flaws is still missing. In this work, we propose a method for estimation of the total passive side-channel information leakage from the Alice's light source. The method relies on Hong-Ou-Mandel interference between different signals emitted by Alice, which reveals their overall mode mismatch without the necessity to measure all individual degrees of freedom independently. We include experimental values of interference visibility in the security proof for the decoy-state BB84 protocol, and lower-bound the secure key rate for realistic light sources. The obtained results provide a tool that can be used for certification of the current QKD systems and pave the way towards the loophole-free design of the future ones.

arXiv:1908.04703•Aug 13, 2019•0 citations

Source-independent quantum key distribution without pre-sending entanglement

Rong-Zheng Liu, Hua-Lei Yin

Quantum key distribution (QKD) theoretically offers information-theoretic security. The prevailing approach is the prepare-and-measure BB84 protocol, which implements QKD using conventional laser rather than single-photon source via the decoy-state method. However, side-channel attacks targeting sources severely threaten system security. Despite extensive efforts, including fully passive scheme, this vulnerability persists even with perfect single-photon source. Here, we propose a source-independent (SI) QKD protocol that resolves all known and unknown source-side attacks without pre-sending entanglement source. Aligning with advances in quantum light sources, our protocol simultaneously doubles the transmission distance while remaining robustness against imperfection of source. Theoretical analysis shows that non-classical light source provides practical security advantages unattainable with conventional laser.

quant-pharXiv:2604.28089•Optics Letters•May 1, 2026•0 citations
Abstract Passive light-source side channel in quantum key distribution (QKD) provides additional information to an eavesdropper via various non-operational degrees of freedom of the optical signal. The currently known explicit eavesdropping strategies aimed at additional information gain from the passive light-source side channel were limited to the attack on the side channel and the operational degree of freedom separately. As a result, their efficiency is far from being optimal. Here we provide the joint eavesdropping strategy on both operational degree of freedom and the passive light-source side channel of the generic form, and develop a method to calculate the corresponding secret key rate. In particular, we use the optimal phase-covariant cloning of the signal photon state followed by a joint collective measurement of the side channel and the operational degree of freedom. To estimate security under the explicit attack strategy, we develop an ‘‘effective error’’ method and demonstrate it on the BB84 protocol with decoy states. Our work extends the practical analysis of QKD protocols with the light-source side channels and can be used as a tool for the analysis of realistic eavesdropping methods.
Abstract Various imperfections of the hardware in quantum key distribution (QKD) lead to discrepancies between the theory and real-world devices. An eavesdropper can use these discrepancies to compromise the QKD security, thus legitimate sides need to estimate the influence of imperfections to prevent the loss of security. Here we investigate explicit eavesdropping attacks on passive side channels of the light source for a BB84 decoy states QKD protocol. We consider an optimal phase-covariant cloning attack, followed by unambiguous state discrimination and a joint measurement. Our calculations provide a hint that for state-of-the-art light sources the inherent presence of passive side channels still allows the protocol to be secure, albeit with the reduced secret key rates.
Abstract Quantum key distribution (QKD) has a promise of unconditionally secure communication between the remote sides. The real-world QKD implementations, however, have numerous loopholes, both of engeneering and physical origin, and compromise the security promise. In this work, we investigate two attack strategies on the passive side channel of the light source along with the optimal cloning attack on the BB84 protocol with decoy-states. We calculate an upper bound of a secret key rate for these situations and show that the joint measurement attack on the signal and side channel degree of freedom is more effective to the adversary.
The distinguishability of photons in nonoperational degrees of freedom compromises the unconditional security of quantum key distribution since an eavesdropper can improve attack strategies by exploiting this distinguishability. However, the optimal eavesdropping strategies in the presence of light-source side channels are not known. Here we provide several explicit attack strategies on the Bennett-Brassard 1984 (BB84) protocol with partially distinguishable photons. In particular, we consider the phase-covariant cloning attack, which is optimal in the absence of side channels, and show that there are even better strategies in the presence of side channels. The improved strategies exploit a measurement of the side-channel state followed by an attack on the signal photon. Our results explicitly demonstrate a reduction of the critical error rate and set an upper bound on the practical secret key rate.
Abstract Quantum key distribution (QKD) promises unconditionally secure communication based on fundamental laws of physics, though practical realizations of QKD may have loopholes and side channels, thus their security can be compromised. We analyze the intercept-resend attack on the BB84 decoy-state protocol under the presence of a passive side channel of the light source. We derive an upper bound for the secret key rate and show that it does not significantly deviate from the ideal side-channel-free case.
Side-channel attacks on practical quantum key distribution systems compromise its security. Although some of these attacks can be taken into account, the general recipe of how to eliminate all side-channel flaws is still missing. In this work, we propose a method for estimation of the total passive side-channel information leakage from the Alice's light source. The method relies on Hong-Ou-Mandel interference between different signals emitted by Alice, which reveals their overall mode mismatch without the necessity to measure all individual degrees of freedom independently. We include experimental values of interference visibility in the security proof for the decoy-state BB84 protocol, and lower-bound the secure key rate for realistic light sources. The obtained results provide a tool that can be used for certification of the current QKD systems and pave the way towards the loophole-free design of the future ones.
Quantum key distribution (QKD) theoretically offers information-theoretic security. The prevailing approach is the prepare-and-measure BB84 protocol, which implements QKD using conventional laser rather than single-photon source via the decoy-state method. However, side-channel attacks targeting sources severely threaten system security. Despite extensive efforts, including fully passive scheme, this vulnerability persists even with perfect single-photon source. Here, we propose a source-independent (SI) QKD protocol that resolves all known and unknown source-side attacks without pre-sending entanglement source. Aligning with advances in quantum light sources, our protocol simultaneously doubles the transmission distance while remaining robustness against imperfection of source. Theoretical analysis shows that non-classical light source provides practical security advantages unattainable with conventional laser.