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

Physical Review A

Proof-of-principle experiment of a modified photon-number-splitting attack against quantum key distribution

Wei-Tao Liu, Shi‐Hai Sun, Lin-Mei Liang, Jianmin Yuan

Published Apr 21, 2011• 22 citations
Publisher

Abstract

Any imperfections in a practical quantum key distribution (QKD) system may be exploited by an eavesdropper to collect information about the key without being discovered. We propose a modified photon-number-splitting attack scheme against QKD systems based on weak laser pulses taking advantage of possible multiphoton pulses. Proof-of-principle experiments are demonstrated. The results show that the eavesdropper can get information about the key generated between the legitimate parties without being detected. Since the equivalent attenuation introduced by the eavesdropper for pulses of different average photon numbers are different, the decoy-state method is effective in fighting against this kind of attack. This has also been proven in our experiments.

DOI
10.1103/physreva.83.042326

Related papers

Wavelength-selected photon-number-splitting attack against plug-and-play quantum key distribution systems with decoy states

Mu-Sheng Jiang, Shi‐Hai Sun, Chunyan Li +1 more

Any imperfections in a practical quantum key distribution (QKD) system may be exploited by an eavesdropper (Eve) to collect information about the key without being discovered. For example, without the decoy-state method, Eve can perform the photon-number-splitting (PNS) attack and get full information without introducing any perturbation, since weak laser pulses are widely used in practical systems instead of single-photon sources. However, the decoy-state method against PNS attack itself may introduce another loophole while closing the loophole of multiphoton pulses. In this paper, a fatal loophole of practical decoy-state plug-and-play QKD systems has been exploited and a wavelength-selected photon-number-splitting (WSPNS) attack scheme against plug-and-play QKD systems with the decoy-state method is proposed. Theoretical analysis shows that the eavesdropper can get full information about the key generated between the legitimate parties just like the PNS attack was performed in plug-and-play QKD systems without the decoy-state method.

Physical Review A•Sep 10, 2012•31 citations

Revealing of photon-number splitting attack on quantum key distribution system by photon-number resolving devices

Andrei Gaidash, V. I. Egorov, Artur V. Gleim

Quantum cryptography allows distributing secure keys between two users so that any performed eavesdropping attempt would be immediately discovered. However, in practice an eavesdropper can obtain key information from multi-photon states when attenuated laser radiation is used as a source of quantum states. In order to prevent actions of an eavesdropper, it is generally suggested to implement special cryptographic protocols, like decoy states or SARG04. In this paper, we describe an alternative method based on monitoring photon number statistics after detection. We provide a useful rule of thumb to estimate approximate order of difference of expected distribution and distribution in case of attack. Formula for calculating a minimum value of total pulses or time-gaps to resolve attack is shown. Also formulas for actual fraction of raw key known to Eve were derived. This method can therefore be used with any system and even combining with mentioned special protocols.

Journal of Physics Conference Series•Aug 1, 2016•16 citations

Detecting the possibility of a type of photon number splitting attack in decoy-state quantum key distribution

Xiao-Ming Chen, Lei Chen, Yalong Yan

The existing decoy-state quantum key distribution (QKD) beating photon-number-splitting (PNS) attack provides a more accurate method to estimate the secure key rate, while it still considers that only single-photon pulses can generate secure keys in any case. However, multiphoton pulses can also generate secure keys if we can detect the possibility of PNS attack in the channel. The ultimate goal of this line of research is to confirm the absence of all types of PNS attacks. In particular, the PNS attack mentioned and detected in this paper is only the weaker version of PNS attack which significantly changes the observed values of the legitimate users. In this paper, under the null hypothesis of no weaker version of PNS attack, we first determine whether there is an attack or not by retrieving the missing information of the existing decoy-state protocols, extract a Cauchy distribution statistic, and further provide a detection method and the type I error probability. If the result is judged to be an attack, we can use the existing decoy-state method and the GLLP formula to estimate the secure key rate. Otherwise, the pulses with the same basis received including both single-photon pulses and multiphoton pulses, can be used to generate the keys and we give the secure key rate in this case. Finally, the associated experiments we performed (i.e., the significance level is 5%) show the correctness of our method.

Chinese Physics B•Oct 17, 2022•2 citations

Enhancing practical security of quantum key distribution with a few decoy states

Jim Harrington, Ettinger, J. Mark, Richard Hughes +1 more

Quantum key distribution establishes a secret string of bits between two distant parties. Of concern in weak laser pulse schemes is the especially strong photon number splitting attack by an eavesdropper, but the decoy state method can detect this attack with current technology, yielding a high rate of secret bits. In this Letter, we develop rigorous security statements in the case of finite statistics with only a few decoy states, and we present the results of simulations of an experimental setup of a decoy state protocol that can be simply realized with current technology.

arXiv:quant-ph/0503002•Mar 1, 2005•33 citations

Coherent-pulse implementations of quantum cryptography protocols resistant to photon-number-splitting attacks

Antonio Acín, Nicolas Gisin, Valerio Scarani

We propose a class of quantum cryptography protocols that are robust against photon-number-splitting attacks (PNS) in a weak coherent-pulse implementation. We give a quite exhaustive analysis of several eavesdropping attacks on these schemes. The honest parties (Alice and Bob) use present-day technology, in particular an attenuated laser as an approximation of a single-photon source. The idea of the protocols is to exploit the nonorthogonality of quantum states to decrease the information accessible to Eve due to the multiphoton pulses produced by the imperfect source. The distance at which the key distribution becomes insecure due to the PNS attack is significantly increased compared to the existing schemes. We also show that strong-pulse implementations, where a strong pulse is included as a reference, allow for key distribution robust against photon-number-splitting attacks.

arXiv:quant-ph/0302037•Physical Review A•Jan 15, 2004•136 citations

Photon-Number Splitting (PNS) Attacks in Weak Coherent Pulse QKD: Simulation and Countermeasures

Sharika Punjabi, Sakshi

For a start, Quantum Key Distribution offers security not depending on any fundamental assumption. However, actual realizations choose to use weak coherent pulses as photon sources, rather than the ideal single-photon state, which bears security weaknesses due to the emission of sporadic multi-photon states. These states can be used in Photon-Number Splitting (PNS) attacks, where the attacker intercepts and buffers photons of multi-photon pulses and forwards the rest, enabling partial recovery of the key without inducing detectable perturbations. This article presents a simulation-based approach to analyze PNS attacks with realistic channel conditions like losses, detector imperfections, and finite key lengths. The research also examines the performance of decoy-state countermeasures, that use variable-intensity pulses to statistically reveal eavesdropping and Simulation results confirm the dominant character of PNS on raw key rates for the no-countermeasure scenario and ensure optimal decoy-state schemes restore security by cutting single-photon contributions. Results establish that although WCP QKD is vulnerable to PNS attacks in theory, strict adoption of decoy-state protocols aided with monitoring and finite-key analysis can provide immunity against an adversary. The paper emphasizes the need for simulation-based, implementation-dependent security analysis in direction towards well-designed practical quantum cryptographic systems. [1] [2] [3] [4] [10] [8]

•Mar 23, 2026•0 citations
Any imperfections in a practical quantum key distribution (QKD) system may be exploited by an eavesdropper to collect information about the key without being discovered. We propose a modified photon-number-splitting attack scheme against QKD systems based on weak laser pulses taking advantage of possible multiphoton pulses. Proof-of-principle experiments are demonstrated. The results show that the eavesdropper can get information about the key generated between the legitimate parties without being detected. Since the equivalent attenuation introduced by the eavesdropper for pulses of different average photon numbers are different, the decoy-state method is effective in fighting against this kind of attack. This has also been proven in our experiments.
Any imperfections in a practical quantum key distribution (QKD) system may be exploited by an eavesdropper (Eve) to collect information about the key without being discovered. For example, without the decoy-state method, Eve can perform the photon-number-splitting (PNS) attack and get full information without introducing any perturbation, since weak laser pulses are widely used in practical systems instead of single-photon sources. However, the decoy-state method against PNS attack itself may introduce another loophole while closing the loophole of multiphoton pulses. In this paper, a fatal loophole of practical decoy-state plug-and-play QKD systems has been exploited and a wavelength-selected photon-number-splitting (WSPNS) attack scheme against plug-and-play QKD systems with the decoy-state method is proposed. Theoretical analysis shows that the eavesdropper can get full information about the key generated between the legitimate parties just like the PNS attack was performed in plug-and-play QKD systems without the decoy-state method.
Quantum cryptography allows distributing secure keys between two users so that any performed eavesdropping attempt would be immediately discovered. However, in practice an eavesdropper can obtain key information from multi-photon states when attenuated laser radiation is used as a source of quantum states. In order to prevent actions of an eavesdropper, it is generally suggested to implement special cryptographic protocols, like decoy states or SARG04. In this paper, we describe an alternative method based on monitoring photon number statistics after detection. We provide a useful rule of thumb to estimate approximate order of difference of expected distribution and distribution in case of attack. Formula for calculating a minimum value of total pulses or time-gaps to resolve attack is shown. Also formulas for actual fraction of raw key known to Eve were derived. This method can therefore be used with any system and even combining with mentioned special protocols.
The existing decoy-state quantum key distribution (QKD) beating photon-number-splitting (PNS) attack provides a more accurate method to estimate the secure key rate, while it still considers that only single-photon pulses can generate secure keys in any case. However, multiphoton pulses can also generate secure keys if we can detect the possibility of PNS attack in the channel. The ultimate goal of this line of research is to confirm the absence of all types of PNS attacks. In particular, the PNS attack mentioned and detected in this paper is only the weaker version of PNS attack which significantly changes the observed values of the legitimate users. In this paper, under the null hypothesis of no weaker version of PNS attack, we first determine whether there is an attack or not by retrieving the missing information of the existing decoy-state protocols, extract a Cauchy distribution statistic, and further provide a detection method and the type I error probability. If the result is judged to be an attack, we can use the existing decoy-state method and the GLLP formula to estimate the secure key rate. Otherwise, the pulses with the same basis received including both single-photon pulses and multiphoton pulses, can be used to generate the keys and we give the secure key rate in this case. Finally, the associated experiments we performed (i.e., the significance level is 5%) show the correctness of our method.
Quantum key distribution establishes a secret string of bits between two distant parties. Of concern in weak laser pulse schemes is the especially strong photon number splitting attack by an eavesdropper, but the decoy state method can detect this attack with current technology, yielding a high rate of secret bits. In this Letter, we develop rigorous security statements in the case of finite statistics with only a few decoy states, and we present the results of simulations of an experimental setup of a decoy state protocol that can be simply realized with current technology.
We propose a class of quantum cryptography protocols that are robust against photon-number-splitting attacks (PNS) in a weak coherent-pulse implementation. We give a quite exhaustive analysis of several eavesdropping attacks on these schemes. The honest parties (Alice and Bob) use present-day technology, in particular an attenuated laser as an approximation of a single-photon source. The idea of the protocols is to exploit the nonorthogonality of quantum states to decrease the information accessible to Eve due to the multiphoton pulses produced by the imperfect source. The distance at which the key distribution becomes insecure due to the PNS attack is significantly increased compared to the existing schemes. We also show that strong-pulse implementations, where a strong pulse is included as a reference, allow for key distribution robust against photon-number-splitting attacks.
For a start, Quantum Key Distribution offers security not depending on any fundamental assumption. However, actual realizations choose to use weak coherent pulses as photon sources, rather than the ideal single-photon state, which bears security weaknesses due to the emission of sporadic multi-photon states. These states can be used in Photon-Number Splitting (PNS) attacks, where the attacker intercepts and buffers photons of multi-photon pulses and forwards the rest, enabling partial recovery of the key without inducing detectable perturbations. This article presents a simulation-based approach to analyze PNS attacks with realistic channel conditions like losses, detector imperfections, and finite key lengths. The research also examines the performance of decoy-state countermeasures, that use variable-intensity pulses to statistically reveal eavesdropping and Simulation results confirm the dominant character of PNS on raw key rates for the no-countermeasure scenario and ensure optimal decoy-state schemes restore security by cutting single-photon contributions. Results establish that although WCP QKD is vulnerable to PNS attacks in theory, strict adoption of decoy-state protocols aided with monitoring and finite-key analysis can provide immunity against an adversary. The paper emphasizes the need for simulation-based, implementation-dependent security analysis in direction towards well-designed practical quantum cryptographic systems. [1] [2] [3] [4] [10] [8]