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:2012.14062 · Physical Review Applied

Perceiving Quantum Hacking for Quantum Key Distribution Using Temporal Ghost Imaging

Fang‐Xiang Wang, Juan Wu, Wei Chen, Shuang Wang, De‐Yong He, Zhen−Qiang Yin, Chang‐Ling Zou, Guang‐Can Guo, Zheng‐Fu Han

Published Mar 17, 2021• 9 citations
arXivHTMLPDF

Abstract

Quantum key distribution (QKD) can generate secure key bits between remote users with quantum mechanics. However, the gap between the theoretical model and practical realizations gives eavesdroppers opportunities to intercept the secret key. The most insidious attacks, known as quantum hacking, are the ones with no significant discrepancy of the measurement results using side-channel loopholes of QKD systems. Depicting full-time-scale characteristics of the quantum signals, the quantum channel, and the QKD system can provide legitimate users extra capabilities to defeat malicious attacks. Here, we propose the method exploring a temporal ghost-imaging (TGI) scheme to perceive quantum hacking with temporal fingerprints and experimentally verify its validity. The scheme presents a common approach to promote QKD's practical security from a unique perspective of signals and systems.

DOI
10.1103/physrevapplied.15.034051

Related papers

Quantum hacking: Experimental demonstration of time-shift attack against practical quantum-key-distribution systems

Yi Bing Zhao, Chi‐Hang Fred Fung, Bing Qi +2 more

Quantum-key-distribution (QKD) systems can send quantum signals over more than $100\phantom{\rule{0.3em}{0ex}}\mathrm{km}$ standard optical fiber and are widely believed to be secure. Here, we show experimentally a technologically feasible attack---namely, the time-shift attack---against a commercial QKD system. Our result shows that, contrary to popular belief, an eavesdropper, Eve, has a non-negligible probability $(\ensuremath{\sim}4%)$ to break the security of the system. Eve's success is due to the well-known detection efficiency loophole in the experimental testing of Bell's inequalities. Therefore, the detection efficiency loophole plays a key role not only in fundamental physics, but also in technological applications such as QKD systems.

arXiv:0704.3253•Physical Review A•Oct 28, 2008•598 citations

Quantum key distribution with hacking countermeasures and long term field trial

A. R. Dixon, J. F. Dynes, Marco Lucamarini +11 more

Quantum key distribution's (QKD's) central and unique claim is information theoretic security. However there is an increasing understanding that the security of a QKD system relies not only on theoretical security proofs, but also on how closely the physical system matches the theoretical models and prevents attacks due to discrepancies. These side channel or hacking attacks exploit physical devices which do not necessarily behave precisely as the theory expects. As such there is a need for QKD systems to be demonstrated to provide security both in the theoretical and physical implementation. We report here a QKD system designed with this goal in mind, providing a more resilient target against possible hacking attacks including Trojan horse, detector blinding, phase randomisation and photon number splitting attacks. The QKD system was installed into a 45 km link of a metropolitan telecom network for a 2.5 month period, during which time the system operated continuously and distributed 1.33 Tbits of secure key data with a stable secure key rate over 200 kbit/s. In addition security is demonstrated against coherent attacks that are more general than the collective class of attacks usually considered.

Scientific Reports•May 10, 2017•46 citations

Temporal ghost imaging for quantum device evaluation

Juan Wu, Fang‐Xiang Wang, Wei Chen +5 more

Ghost imaging (GI) can reconstruct the image of an object by measuring the correlation function of two beams, none of which carries the structure information of the object independently. This powerful technology makes it possible to obtain high-quality imaging of the object even in the presence of noise. Here, we introduce the GI method into quantum device evaluation in the time domain. We realized a proof-of-principle experiment to evaluate the temporal detection efficiency of a gated-mode single-photon avalanche detector (SPAD). The experimental results show that high-quality evaluation of temporal characteristics of the SPAD can be realized by the method of temporal GI (TGI). Our work indicates that the TGI method is an effective tool to monitor the temporal characteristics of quantum devices in real time and will bring a new perspective to the security evaluation of quantum communication.

Optics Letters•May 9, 2019•18 citations

Quantum Hacking in the Age of Measurement-Device-Independent Quantum Cryptography

Anqi Huang

Cryptography is essential for secure communication in the digital era. Today, public-key cryptography is widely employed, and has provided an efficient method for encrypting content and ensuring both confidentiality and authenticity of electronic communications. However, the security of these systems is based on assumptions of computational hardness within the constraints of current computing capability. Thus, as quantum computing becomes a reality, public-key algorithms will be genuinely vulnerable to attack. By contrast, quantum cryptography, which is based on quantum physics instead of mathematical assumptions, is able to achieve information-theoretic security. \n \nAdvances in practical quantum cryptographic systems have not kept pace with theory, where an eavesdropper can relatively easily exploit loopholes in practical implementations to compromise theory-proved security. Bridging the gap between perfect theory and imperfect practice has become a priority for the growing field of quantum key distribution (QKD), which has strived to strengthen the practical security of QKD systems. Among all the countermeasures against quantum hacking, the measurement-device-independent (MDI) QKD protocol is promising because it is immune to all side-channel attacks on measurement devices. However, the MDI QKD protocol has some limitations that critically restrict its practical usefulness. Technically, the MDI scheme is not compatible with existing QKD systems, and produces a low key rate. In addition, the theory underlying MDI QKD security is based on the use of trusted source stations. Thus, this protocol is not a universal solution. This thesis further investigates the practical security of quantum cryptography in and beyond MDI quantum cryptography. \n \nTo overcome the technical limitations of MDI QKD, we first evaluate two other countermeasures against imperfect detections. The first is an industrial patch based on random detection efficiency, recently implemented by ID Quantique in the commercial Clavis2 QKD system. While powerful, experimental testing shows that this countermeasure is not sufficient to defeat the detector blinding attack. The second countermeasure aims to achieve a higher key rate than MDI QKD while maintaining the same security properties. However, our research shows that detector-device-independent (DDI) QKD security is not equivalent to that of MDI QKD and, further, that DDI QKD is insecure against detector side-channel attacks. \n \nWhile this initial work points to the superior performance of MDI QKD systems, core challenges remain. The fundamental security assumption adopted for MDI QKD systems, regarding the exclusive use of trustable source stations, cannot always be satisfied in practice. Our study revealed several side channels of source devices. The first is disclosed from the implementation of a decoy-state protocol, which is widely used in QKD systems with weak coherent sources. The pump-current-modulated intensities result in a timing mismatch between the signal and decoy states, violating the key assumption in the decoy-state QKD protocol. Moreover, an active Eve can break the basic assumption about photon numbers in the QKD system. In this work, we experimentally demonstrate a laser seeding attack on the laser source, which shows that Eve can increase the emission power of the laser diode. Furthermore, by shining a high-power laser into an optical attenuator, Eve can decrease the attenuation values. The increase in laser emission power and the decrease in attenuation leads to an increase in mean photon numbers. \n \nIn summary, MDI QKD is a milestone in quantum cryptography. However, this thesis indicates the importance of continued investigations into the practical security of MDI QKD. The analysis of practical security should be extended to other countermeasures against side-channel attacks and the source stations in MDI QKD systems. Practical quantum hacking and security analysis promote the development of quantum cryptographic systems, which will eventually achieve the unconditional security claimed in theory.

•Apr 13, 2018•3 citations

Enhancing Quantum Key Distribution (QKD) to address quantum hacking

Luis Adrián Lizama-Pérez, J. Mauricio López, Eduado De Carlos López +1 more

Quantum key distribution (QKD) is intended to produce cryptographic secret keys between two remote parties, usually called Alice and Bob. Even though QKD has been proven to be unconditionally secure against the eavesdropper, commonly called Eve, practical implementations of QKD may contain vulnerabilities that may lead to the generated secret keys being compromised. In order to detect the presence of the eavesdropper in the channel, in our proposal Alice introduces an interleaved sequence of decoy states which produce a characteristic distribution at Bob's station. Thus, in analyzing such distribution in presence and absence of the eavesdropper Eve, her activity in the channel is detected. This protocol doesn’t require changes at the quantum physical level, but it can be incorporated at the high software level.

Procedia Technology•Jan 1, 2012•11 citations

Experimental study of time-dependent side channels in quantum key distribution

Hao Tan, Weiyang Zhang, Liying Han +2 more

Quantum key distribution allows remote parties to share secret keys with proven security. However, in most systems, these schemes will also modulate light that gets leaked between the signal pulses, resulting in time-dependent side channels. Here, the authors experimentally study practical quantum key distribution with these side channels, analyzing the security risks and the corresponding countermeasures.

Physical Review A•Apr 28, 2025•2 citations
Quantum key distribution (QKD) can generate secure key bits between remote users with quantum mechanics. However, the gap between the theoretical model and practical realizations gives eavesdroppers opportunities to intercept the secret key. The most insidious attacks, known as quantum hacking, are the ones with no significant discrepancy of the measurement results using side-channel loopholes of QKD systems. Depicting full-time-scale characteristics of the quantum signals, the quantum channel, and the QKD system can provide legitimate users extra capabilities to defeat malicious attacks. Here, we propose the method exploring a temporal ghost-imaging (TGI) scheme to perceive quantum hacking with temporal fingerprints and experimentally verify its validity. The scheme presents a common approach to promote QKD's practical security from a unique perspective of signals and systems.
Quantum-key-distribution (QKD) systems can send quantum signals over more than 100km100\phantom{\rule{0.3em}{0ex}}\mathrm{km}100km standard optical fiber and are widely believed to be secure. Here, we show experimentally a technologically feasible attack---namely, the time-shift attack---against a commercial QKD system. Our result shows that, contrary to popular belief, an eavesdropper, Eve, has a non-negligible probability $(\ensuremath{\sim}4%)$ to break the security of the system. Eve's success is due to the well-known detection efficiency loophole in the experimental testing of Bell's inequalities. Therefore, the detection efficiency loophole plays a key role not only in fundamental physics, but also in technological applications such as QKD systems.
Quantum key distribution's (QKD's) central and unique claim is information theoretic security. However there is an increasing understanding that the security of a QKD system relies not only on theoretical security proofs, but also on how closely the physical system matches the theoretical models and prevents attacks due to discrepancies. These side channel or hacking attacks exploit physical devices which do not necessarily behave precisely as the theory expects. As such there is a need for QKD systems to be demonstrated to provide security both in the theoretical and physical implementation. We report here a QKD system designed with this goal in mind, providing a more resilient target against possible hacking attacks including Trojan horse, detector blinding, phase randomisation and photon number splitting attacks. The QKD system was installed into a 45 km link of a metropolitan telecom network for a 2.5 month period, during which time the system operated continuously and distributed 1.33 Tbits of secure key data with a stable secure key rate over 200 kbit/s. In addition security is demonstrated against coherent attacks that are more general than the collective class of attacks usually considered.
Ghost imaging (GI) can reconstruct the image of an object by measuring the correlation function of two beams, none of which carries the structure information of the object independently. This powerful technology makes it possible to obtain high-quality imaging of the object even in the presence of noise. Here, we introduce the GI method into quantum device evaluation in the time domain. We realized a proof-of-principle experiment to evaluate the temporal detection efficiency of a gated-mode single-photon avalanche detector (SPAD). The experimental results show that high-quality evaluation of temporal characteristics of the SPAD can be realized by the method of temporal GI (TGI). Our work indicates that the TGI method is an effective tool to monitor the temporal characteristics of quantum devices in real time and will bring a new perspective to the security evaluation of quantum communication.
Cryptography is essential for secure communication in the digital era. Today, public-key cryptography is widely employed, and has provided an efficient method for encrypting content and ensuring both confidentiality and authenticity of electronic communications. However, the security of these systems is based on assumptions of computational hardness within the constraints of current computing capability. Thus, as quantum computing becomes a reality, public-key algorithms will be genuinely vulnerable to attack. By contrast, quantum cryptography, which is based on quantum physics instead of mathematical assumptions, is able to achieve information-theoretic security. \n \nAdvances in practical quantum cryptographic systems have not kept pace with theory, where an eavesdropper can relatively easily exploit loopholes in practical implementations to compromise theory-proved security. Bridging the gap between perfect theory and imperfect practice has become a priority for the growing field of quantum key distribution (QKD), which has strived to strengthen the practical security of QKD systems. Among all the countermeasures against quantum hacking, the measurement-device-independent (MDI) QKD protocol is promising because it is immune to all side-channel attacks on measurement devices. However, the MDI QKD protocol has some limitations that critically restrict its practical usefulness. Technically, the MDI scheme is not compatible with existing QKD systems, and produces a low key rate. In addition, the theory underlying MDI QKD security is based on the use of trusted source stations. Thus, this protocol is not a universal solution. This thesis further investigates the practical security of quantum cryptography in and beyond MDI quantum cryptography. \n \nTo overcome the technical limitations of MDI QKD, we first evaluate two other countermeasures against imperfect detections. The first is an industrial patch based on random detection efficiency, recently implemented by ID Quantique in the commercial Clavis2 QKD system. While powerful, experimental testing shows that this countermeasure is not sufficient to defeat the detector blinding attack. The second countermeasure aims to achieve a higher key rate than MDI QKD while maintaining the same security properties. However, our research shows that detector-device-independent (DDI) QKD security is not equivalent to that of MDI QKD and, further, that DDI QKD is insecure against detector side-channel attacks. \n \nWhile this initial work points to the superior performance of MDI QKD systems, core challenges remain. The fundamental security assumption adopted for MDI QKD systems, regarding the exclusive use of trustable source stations, cannot always be satisfied in practice. Our study revealed several side channels of source devices. The first is disclosed from the implementation of a decoy-state protocol, which is widely used in QKD systems with weak coherent sources. The pump-current-modulated intensities result in a timing mismatch between the signal and decoy states, violating the key assumption in the decoy-state QKD protocol. Moreover, an active Eve can break the basic assumption about photon numbers in the QKD system. In this work, we experimentally demonstrate a laser seeding attack on the laser source, which shows that Eve can increase the emission power of the laser diode. Furthermore, by shining a high-power laser into an optical attenuator, Eve can decrease the attenuation values. The increase in laser emission power and the decrease in attenuation leads to an increase in mean photon numbers. \n \nIn summary, MDI QKD is a milestone in quantum cryptography. However, this thesis indicates the importance of continued investigations into the practical security of MDI QKD. The analysis of practical security should be extended to other countermeasures against side-channel attacks and the source stations in MDI QKD systems. Practical quantum hacking and security analysis promote the development of quantum cryptographic systems, which will eventually achieve the unconditional security claimed in theory.
Quantum key distribution (QKD) is intended to produce cryptographic secret keys between two remote parties, usually called Alice and Bob. Even though QKD has been proven to be unconditionally secure against the eavesdropper, commonly called Eve, practical implementations of QKD may contain vulnerabilities that may lead to the generated secret keys being compromised. In order to detect the presence of the eavesdropper in the channel, in our proposal Alice introduces an interleaved sequence of decoy states which produce a characteristic distribution at Bob's station. Thus, in analyzing such distribution in presence and absence of the eavesdropper Eve, her activity in the channel is detected. This protocol doesn’t require changes at the quantum physical level, but it can be incorporated at the high software level.