The simulation method of decoy-state based on coherent states was proposed in this paper.We analyze the yield ratio of decoy pulses and signal pulses at the output,and verified the effectiveness of decoy state in overcoming the photon-number-splitting(PNS) attack.In addition,we take the yield ratio as a threshold that used to examine whether there exist a PNS attack.We simulate the average photon number 0,0.2,0.6,as the vacuum,signal and decoy,respectively.In the case of the channel loss is 0.2dB/km,detection efficiency is 20%,and dark count is 10-5,the results of simulation show the secure communication distance is up to 140km.Due to the classical computer simulation,a new scheme for quantum information research is provided.
The simulation method of decoy-state based on coherent states was proposed in this paper.We analyze the yield ratio of decoy pulses and signal pulses at the output,and verified the effectiveness of decoy state in overcoming the photon-number-splitting(PNS) attack.In addition,we take the yield ratio as a threshold that used to examine whether there exist a PNS attack.We simulate the average photon number 0,0.2,0.6,as the vacuum,signal and decoy,respectively.In the case of the channel loss is 0.2dB/km,detection efficiency is 20%,and dark count is 10-5,the results of simulation show the secure communication distance is up to 140km.Due to the classical computer simulation,a new scheme for quantum information research is provided.
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]
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]
With the potential of quantum computers to compromise current public-key cryptosystems, Quantum Key Distribution (QKD), which is based on the physical laws of quantum mechanics, has garnered significant attention. However, while QKD security proofs typically assume ideal single-photon sources, realistic implementations rely on Weak Coherent Pulses (WCP) due to the difficulties associated with commercializing true single-photon sources. Unfortunately, the multi-photon components inherent in WCPs are vulnerable to Photon Number Splitting (PNS) attacks, which limits the secure transmission distance to a few tens of kilometers. This article introduces the Decoy State method, which effectively resolves this issue. Proposed by W.-Y. Hwang in 2003 and further advanced by H.-K. Lo and X.-B. Wang, this technique utilizes the random interleaving of pulses with different mean photon numbers during transmission. By doing so, it enables the accurate estimation of single-photon yield and error rates, thereby effectively detecting PNS attacks. Because it can be implemented using standard commercial lasers and intensity modulators, the Decoy State method has become the standard technology in most modern QKD systems. It serves as a core component for long-distance quantum communication, enabling major milestones reported recently. This article reviews the principles, mathematical analysis, and latest applications of the Decoy State method.
Abstract The decoy state method has been proposed to detect a photon number splitting (PNS) attack. Today, the decoy state method is considered to be an almost universal method for proving the secrecy of quantum cryptography protocols and calculating the length of a secret key. In this paper, it is shown that there exist attacks, for example, a beam splitting (BS) attack, to which the decoy state method turns out to be insensitive. The decoy state method is oriented to the detection of changes in the photocount statistics of information states and decoy states under a PNS attack. Under a BS attack, the photocount statistics is not changed. As a result, the decoy state method significantly overestimates the length of the key. Thus, the decoy state method is not a universal method that allows the detection of various attacks. Apparently, due to a large number of publications on the decoy state method, a widespread opinion has been formed that this method is universal. This fact has led to attempts to adopt this method as an international standard in quantum cryptography, which is clearly premature.
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.
Nonorthogonal coded agreements and decoy state method can effectively protect the photon number against splitting attack. Owing to the fact that the component of single-photon in the coherent-state superposition (CSS) is as high as 90%, CSS has recently emerged as an alternative to single-photon qubits for quantum information processing and metrology. The approximate CSS of small amplitudes is generated by the subtraction of photons from a squeezed vacuum state, and the approximate CSS of large amplitude is generated from Fock state by using a single homodyne detection. Here, we combine both of the methods and propose a new protocol by using the CSS as a light source. We derive the secure key generation rate, the lower bound of count rate and upper bound of error rate of single-photon. We simulate the curves relationship between secure key generation rate and safety transmission distance in the case of an infinite number of decoy states by using matlab. The parameters are given according to the Gobby-Yuan-Shields (GYS) experiment. We infer that the safety transmission distance achieves 147.4 km and the secure key generation rate is much higher than those of other schemes. We also simulate the relationship between key generation rate and safety transmission distance in the case of a limited number of decoy states by using matlab. The parameters are given according to the GYS experiment too. When the N is 1010, the safety transmission distance achieves 144 km; when the N is 109, the safety transmission distance achieves 139 km; when the N is 108, the safety transmission distance achieves 125.9 km. In this paper, we propose the use of CSS as the light source. Combining SARG04 agreements and decoy state, the scheme has the following advantages: first, the scheme which combines SARG04 agreements and decoy state method can effectively resist PNS; second, nonorthogonal decoy-state quantum key distribution based on coherent-state superpositions has a longer safety transmission distance and higher secure key generation rate than nonorthogonal decoy-state quantum key distribution based on weak coherent pulse and nonorthogonal decoy-state quantum key distribution based on conditionally prepared down-conversion source; third, nonorthogonal decoy-state quantum key distribution based on coherent-state superpositions is easier to prepare, which just needs one decoy state, than other schemes that require several decoy states. Obviously, our scheme can enhance the performance of quantum key distribution. Nonorthogonal decoy-state quantum key distribution based on coherent-state superpositions will have a very good application with the further development of preparation technology of CSS.