Topical Review: Optimum Probe Parameters for Entangling Probe in Quantum Key Distribution

For the four-state protocol of quantum key distribution, optimum sets of probe parameters are calculated for the most general unitary probe in which each individual transmitted photon is made to interact with the probe so that the signal and the probe are left in an entangled state, and projective measurement by the probe, made subsequent to projective measurement by the legitimate receiver, yields information about the signal state. The probe optimization is based on maximizing the Renyi information gain by the probe on corrected data for a given error rate induced by the probe in the legitimate receiver. An arbitrary angle is included between the nonorthogonal linear polarization states of the signal photons. Two sets of optimum probe parameters are determined which both correspond to the same optimization. Also, a larger set of optimum probe parameters is found than was known previously for the standard BB84 protocol. A detailed comparison is made between the complete and incomplete optimizations, and the latter simpler optimization is also made complete. Also, the process of key distillation from the quantum transmission in quantum key distribution is reviewed, with the objective of calculating the secrecy capacity of the four-state protocol in the presence of the eavesdropping probe. Emphasis is placed on information leakage to the probe. PACS: 03.67.Dd; 03.67.Hk; 03.65.Ta     

Performance Analysis for Brandt’s Conclusive Entangling Probe

The Fuchs–Peres–Brandt (FPB) probe realizes the most powerful individual attack on Bennett-Brassard 1984 quantum key distribution by means of a single controlled-NOT gate in which Alice’s transmitted qubit becomes the control-qubit input, Bob’s received qubit is the control-qubit output, and Eve supplies the target-qubit input and measures the target-qubit output. The FPB probe uses the minimum-error-probability projective measurement for discriminating between the target-qubit output states that are perfectly correlated with Bob’s sifted bit value when that bit is correctly received. This paper analyzes a recently proposed modification of the FPB attack in which Eve’s projective measurement is replaced by a probability operator-valued measurement chosen to unambiguously discriminate between the same two target-qubit output states. PACS: 03.67.Dd, 03.67.Hk, 03.65.Ta.     

Unambiguous State Discrimination in Quantum Key Distribution

The quantum circuit and design are presented for an optimized entangling probe attacking the BB84 Protocol of quantum key distribution (QKD) and yielding maximum information to the probe. Probe photon polarization states become optimally entangled with the signal states on their way between the legitimate transmitter and receiver. Although standard von-Neumann projective measurements of the probe yield maximum information on the pre-privacy amplified key, if instead the probe measurements are performed with a certain positive operator valued measure (POVM), then the measurement results are unambiguous, at least some of the time. It follows that the BB84 (Bennett–Brassard 1984) protocol of quantum key distribution has a vulnerability similar to the well-known vulnerability of the B92 (Bennett 1992) protocol Pacs: 03.67.Dd, 03.67.Hk, 03.65.Ta     

基于量子单向函数的身份认证和密钥分配协议

研究量子单向函数和信息分割原理,提出一种身份认证和密钥分配协议。使用可信服务器为示证者提供随机身份信息,以完成认证过程的确认,在密钥分配的同时进行认证,利用量子单向函数提高认证的安全性。实验结果表明,该协议涉及的量子通信技术易于实现,能提高密钥的分配效率。     

Security of Practical Time-Reversed EPR Quantum Key Distribution

Abstract. We propose a proof of the security of a time-reversed EPR quantum key distribution protocol against enemies with unlimited computational power. The considered protocol uses interactive key distillation, and the proof holds for implementations using imperfect photon sources.     

Security of Practical BB84 Quantum Key Distribution

Abstract. We propose a proof of the security of a practical BB84 quantum key distribution protocol against enemies with unlimited computational power. The considered protocol uses interactive key distillation, and the proof holds for implementations using imperfect optical devices.     

QKD网络中组密钥协商的研究

传统组密钥协商方法很难满足QKD(Quantum Key Distribution)网络的实用需求。针对这种情况,提出一种适用于多种QKD网络结构的复合式量子组密钥协商方案。该方案将不同结构的QKD网络归为统一的形式,充分利用密钥缓存池中的密钥,在经典信道上完成安全协商过程,最终参与组播通信的QKD设备都能获得一致的组密钥,并将这些密钥分发给用户。与几种传统组密钥协商方案对比,该方案具有很好的安全性和可扩展性,并在绝大数应用环境下具有很高的效率。     

基于QCircuit的BB84窃听仿真与分析

该文研究量子线路模型仿真量子密钥分配协议.基于QCircuit软件运用量子线路模型设计不同攻击模型下的BB84量子密钥分配协议仿真模型,并引入rsec和I(α,E)两个指标,设计指标分析线路模型,仿真分析了不同噪声信道模型下BB84密钥分配协议在P/P、B/P和B/B三种不同截取/重发策略下的有效性及安全性.仿真结果表...     

基于纠缠的量子密钥分配协议仿真

由于受物理资源和实验条件的限制,在经典计算机上对量子密钥分配（QKD）仿真,为研究者提供一种手段以便更好地掌握这类抽象协议。对以纠缠态为基础的E91协议的量子密钥分配过程进行仿真,重点对比分析了理想环境、有噪环境以及窃听环境下的仿真结果,并验证该量子密钥分配协议的安全性。     

一种基于[7,1]CSS纠错码的量子密钥分配协议

量子密钥分配协议具有可证明的绝对安全性,但是由于量子信道噪声的作用,量子比特在传输过程中容易产生错误,从而降低量子密钥分配的效率.对此,根据量子纠错理论,利用Hamming码构造一种[7,1]CSS纠错码,并结合BB84协议,提出一种改进的量子密钥分配协议.通过理论分析与数值计算,对比改进协议与BB84协议在含噪声量子...     

量子密码研究与进展

量子密码解决了传统密码技术存在的问题,是近年来国际学术界的一个研究热点。本文论述了传统密码技术存在的问题,阐述了量子密码的基本原理,介绍了主要的量子密码协议：BB84协议、B92协议和E91协议等,并研究了量子密码通信的研究现状及其进展。量子密码必将会在网络安全通信中得到广泛的应用。     

量子密码学的研究进展

量子密码术是一种新的重要加密方法，它利用单光子的量子性质，借助量子密钥分配协议可实现数据传输的可证性安全．量子密码具有无条件安全的特性(即不存在受拥有足够时间和计算机能力的窃听者攻击的危险)，而在实际通信发生之前，不需要交换私钥．本文综述了量子密码学的研究进展，其中包括了量子密码学的物理基础、量子密钥分配、保密增强、量子密钥的实用性以及目前技术限制所存在的缺陷．     

量子密码通信及其研究进展

2007年4月2日,国际上首个量子密码通信网络由中国科学家在北京测试运行成功。这是迄今为止国际公开报道的唯一无中转,可同时、任意互通的量子密码通信网络,标志着量子保密通信技术从点对点方式向网络化迈出了关键一步。这次实验的成功,为量子因特网的发展奠定了基础。文章阐述量子密码的产生、量子密码学的基本原理、该领域的实验研究及研究成果,最后指出量子密码通信将是保障未来网络通信安全的一种重要技术。     

The influence of stochastic dispersion on quantum key distribution system

By theoretical calculation and analysis, this paper studies the influence of stochastic fiber dispersion on interference stability and erroneous detected rate of quantum key distribution （QKD） system receiver, and analyses its effects on quantum key generation rates of decoy states QKD. The result shows that the interference contrast and erroneous detected rate of the system will be affected by real part only but not by imaginary part only. However, when the real part exists, the imaginary part will have an effect on the interference contrast and erroneous detected rate.     

有噪声的BB84量子密码协议的改进

把量子力学应用到密码学中产生了一个新的学科———量子密码学。量子密码提供的密钥交换方式,能够自动检查是否有人在窃听,这是公钥体制所不具备的。该文对有噪声的BB84协议作了一些改进,以增强安全性、提高效率。这种改进方案对其它带有噪声的量子密码协议同样适用。     

Another Alternative to Quantum Cryptography

Quantum cryptography has several unorthodox attributes: it is invulnerable to passive eavesdropping; communicators need no initial shared secret (cryptographic key), but they do need an auxiliary tamper-proof link; the scheme requires an uninterrupted light path (no repeater), and a one-time pad of keystream must be prepared in advance of the secure transmission. At least two other cryptologic schemes share these same attributes. This is quite remarkable because each of the three schemes has an entirely different physical basis for its message secrecy. In quantum cryptography an eavesdropper cannot measure or clone the state of a photon without revealing the attempt to the authorized receiver. The second scheme is the Yuen–Kim protocol. Potential bits for the keystream are masked by classical noise. The eavesdropper cannot extract the same useful bits that the authorized receiver extracts because their receivers are statistically independent. Our own scheme, called QDRN, distributes broadband noisy light to terminals, where interferometers provide identical keystreams. Security presumes that there exists some bandwidth broad enough so that the eavesdropper cannot store the phase information either optically or digitally for some period like minutes, or even hours if necessary, after which the users may safely transmit data. The Yuen–Kim protocol is by far the simplest to implement. However, it is limited to point-to-point links and distances of some tens of kilometers. By contrast, QDRN operates with full power, is compatible with amplifiers and networks, and extends to hundreds of kilometers, quite possibly a megameter. PACS: 03.67.Dd     

量子计算与量子密码的原理及研究进展综述

量子计算与量子密码是基于量子效应的计算技术和密码技术.1984年Bennett和Brassard提出了第一个量子密钥分发协议,开启了量子密码学的研究,此后相继在量子加密、量子签名等领域进行了大量研究.1994年,Shor利用量子Fourier变换,设计了第一个实用的量子算法,在多项式时间内对大整数进行因子分解.1996年,Grover提出了量子搜索算法,能够对无结构数据进行二次加速.Shor算法和Grover算法的提出不仅体现了量子计算的优越性,还对传统基于数学困难问题的密码学体制造成威胁.经过半个世纪的发展,量子计算与量子密码在理论与实践的研究上都取得了丰硕的成果.从量子力学的数学框架、基本概念和原理、量子计算基本思想、量子密码研究进展及主要思想等方面进行总结梳理.     

量子密码理论研究进展

21世纪信息空间的开发、利用和对抗无疑成为各国科技发展的战略高点。近年来,量子信息技术的快速发展拓宽了信息理论的研究内容,也给信息科学研究带来了新的机遇与挑战。介绍了量子计算理论对现代密码学的重要影响,建立了量子保密通信模型,给出了几类量子攻击模式。分析了量子密钥分配、量子消息加密和量子数字签名等理论和技术的研究新进展,对未来几类重点研究问题进行了总结和展望。     

测量设备无关量子密钥分发中的改进型诱骗态方法

测量设备无关量子密钥分发协议作为量子网络的候选组件之一,消除了探测端的所有漏洞,提升了系统安全性。目前的测量设备无关量子密钥分发协议采用非理想单光子源,并引入了诱骗态方法来提高密钥率。最近,一种整合在诱骗态方法中的数据后处理方法双扫描法在统计波动方面表现出色。使用诱骗态方法估算单光子对成分时,引入双扫描法能获得更高的密钥率。然而,双扫描法需要耗时的优化过程。在此,文章提出了一种新颖的改进型诱骗态方法,以实现比原始诱骗态方法更好的性能,同时避免了类似双扫描法优化时间的出现。在文章所有的实验参数值模拟中,改进型诱骗态方法均比原始诱骗态方法的密钥率更高;相较于双扫描法,文章所提方法具有速度快、兼容性好的优点。     

Enhancing the security of quantum communication by hiding the message in a superposition

A new method to hide specific quantum states in a superposition will be proposed. The proposed method is used to hide an encrypted message in a superposition. The process of hiding and unhiding the target quantum states is fast by using a single iteration of the amplitude amplification operators. This makes the message 100% safe by direct measurement from an eavesdropper. No entanglement sharing is required among the communicating parties.