How Secure Are Two-Way Ping-Pong and LM05 QKD Protocols under a Man-in-the-Middle Attack?

We consider a man-in-the-middle attack on two-way quantum key distribution ping-pong and LM05 protocols in which an eavesdropper copies all messages in the message mode, while being undetectable in the mode. Under the attack there is therefore no disturbance in the message mode and the mutual information between the sender and the receiver is always constant and equal to one and messages copied by the eavesdropper are always genuine. An attack can only be detected in the control mode but the level of detection at which the protocol should be aborted is not defined. We examine steps of the protocol to evaluate its security and find that the protocol should be redesigned. We also compare it with the security of a one-way asymmetric BB84-like protocol in which one basis serves as the message mode and the other as the control mode but which does have the level of detection at which the protocol should be aborted defined.     

Comparing the efficiencies of different detect strategies in the ping-pong protocol

The way to compare the efficiencies of different detect strategies (DSs) in the “ping-pong” protocol is studied. The trade-off between information gain and disturbance is calculated and compared for different DSs. The comparison result primely tallies with our intuitional analysis. It is shown that the analysis of this trade-off is a feasible way to compare the performances of different DSs in theory. Supported by the National High Technology Research and Development Program of China (Grant No. 2006AA01Z419), the National Natural Science Foundation of China (Grant Nos. 90604023 and 6087319), the National Laboratory for Modern Communications Science Foundation of China (Grant No. 9140C1101010601), the Natural Science Foundation of Beijing (Grant No. 4072020), and the ISN Open Foundation.     

Quantum key distribution using three basis states

This note presents a method of public key distribution using quantum communication of n photons that simultaneously provides a high probability that the bits have not been tampered. It is a variant of the quantum method of Bennett and Brassard (BB84) where the transmission states have been decreased from 4 to 3 and the detector states have been increased from 2 to 3. Under certain assumptions regarding method of attack, it provides superior performance (in terms of the number of usable key bits) for n<18m, where m is the number of key bits used to verify the integrity of the process in the BB84-protocol.     

Failure of Kak quantum key distribution protocol

Kak’s quantum key distribution (QKD) protocol provides not only the distribution but also the integrity of secret key simultaneously in quantum channel. Consequently the additional exchange of information, used to check whether an eavesdropper exists, is unnecessary. In this comment, we will point out the failure of Kak’s protocol and show that Kak’s protocol does not have the joint distribution and integration that the author declares in [1].     

量子密码--新一代密码技术

本文阐述了量子密码的基本原理，着重介绍了光纤量子密码研究的最新进展。     

Security analysis on some experimental quantum key distribution systems with imperfect optical and electrical devices

In general, quantum key distribution （QKD） has been proved unconditionally secure for perfect devices due to quantum uncertainty principle, quantum noneloning theorem and quantum nondividing principle which means that a quantum cannot be divided further. However, the practical optical and electrical devices used in the system are imperfect, which can be exploited by the eavesdropper to partially or totally spy the secret key between the legitimate parties. In this article, we first briefly review the recent work on quantum hacking on some experimental QKD systems with respect to imperfect devices carried out internationally, then we will present our recent hacking works in details, including passive faraday mirror attack, partially random phase attack, wavelength-selected photon-number-splitting attack, frequency shift attack, and single-photon-detector attack. Those quantum attack reminds people to improve the security existed in practical QKD systems due to imperfect devices by simply adding countermeasure or adopting a totally different protocol such as measurement-device independent protocol to avoid quantum hacking on the imperfection of measurement devices [Lo, et al., Phys. Rev. Lett., 2012, 108： 130503].     

基于随机相位编码的确定性量子密钥分配

提出一种新的随机相位编码的确定性量子密钥分配(QKD)方案.在该方案中,通信双方不需要公布测量基,就可以共享秘密信息,提高了密钥生成效率.因为传输的量子比特是随机编码的,即便光源非严格为单光子,该方案仍旧是安全的.理论分析显示出,对于光子数分裂攻击,中间人攻击和特洛伊木马等攻击手段,本方案比之前的QKD方案具有更强的安全性.     

运行双协议相位调制的量子密钥分发系统

基于差分编码方式提出一种改进方案.在Alice端用光纤马赫-曾德干涉仪产生双脉冲差分信号;在Bob端,用双法拉第反射式麦克尔逊干涉仪代替光纤马赫-曾德干涉仪,这种干涉仪能自动补偿环境引起的偏振抖动和光纤双折射引起的相位漂移,从而提高系统稳定性.双协议(即双脉冲差分协议联合BB84协议)的使用,增强了系统的安全性.该系统具有高效、安全、简洁、稳定等优点,在实验上实现了长期稳定的密钥分发和量子保密通信,误码率<5%,传输距离达80km.     

Quantum Key Distribution Based on Coherent States

Ｏｎｅｏｆｔｈｅｍｏｓｔｉｎｔｒｉｇｕｉｎｇａｎｄｅｘｃｉｔｉｎｇｒｅｃｅｎｔｄｅｖｅｌｏｐｍｅｎｔｓｉｎｑｕａｎｔｕｍｍｅｃｈａｎｉｃｓｉｓｔｈｅｐｒｅｄｉｃｔｉｏｎａｎｄｄｅｍｏｎｓｔｒａｔｉｏｎｏｆａｃｒｙｐｔｏｇｒａｐｈｉｃｋｅｙｄｉｓｔｒｉ...     

长距离长期稳定的量子密钥分发系统

介绍了最近完成的长距离长期稳定的量子密钥分发系统.该系统利用往返光路补偿光纤偏振 抖动和相位漂移的原理,采用结电容平衡魔T网络耦合的单光子探测技术,在506km单模 光纤中实现了长时间（大于12h）稳定的量子密钥分发实验.单脉冲平均光子数为007, 误码率为4%,其中单光子探测器的探测效率大于5%,单脉冲暗计数低于29×10^{-6.关键词：量子保密通信量子密钥分发单光子探测}     

高稳定的差分相位编码量子密钥分发系统

在差分法基础上提出了一种改进的差分相位编码量子密钥分发(QKD)方案.Alice采用脉冲激光光源,通过两个串联光纤延迟环产生四个均匀的相干脉冲,并对脉冲进行差分调制,补偿了传输过程中环境对偏振的扰动.Bob采用双FM干涉仪,在窄脉冲门控模式下进行单光子探测.单程传输避免了木马攻击,增强了方案的安全性.实验结果表明,系统可以长期稳定运转(大于24h),误码率为3％.改进的系统具有高效、稳定、低成本的优点,实施方便,有很好的实用价值.关键词：量子保密通信量子密钥分发差分相位编码     

1550 nm单模光纤中的量子密钥分配

从实验中实现了红外波段的远程量子密钥分配。系统采用双不等臂M-Z干涉仪相位编码方式,工作波长为1550nm。通过分析量子密钥分配系统传输距离与误码率之间相互关系,给出了理论上理想不等臂M-Z系统与实际系统的最低误码率与传输距离间的关系,以及系统实测传输距离与误码率的关系。实验结果显示,本密钥分配系统已非常接近理想实验系统的性能。     

量子通信研究进展与应用

量子通信利用量子信道进行信息的编码、传输和处理,具有安全性高和信道容量高等特点。量子保密通信以信息安全为主要目的,包括量子密钥分发、量子安全直接通信和量子秘密共享等模式。利用量子纠缠,量子隐形传态根据事先已经分发的纠缠粒子对实现不传输实物粒子而传输未知粒子的状态,量子密集编码通过传输一个粒子而实现两个粒子信息的传输,这些是经典通信无法实现的任务。文章简单介绍量子通信的内容和进展情况。     

基于量子隐形传态的量子保密通信方案

量子保密通信包括量子密钥分发、量子安全直接通信和量子秘密共享等主要形式.在量子密钥分发和秘密共享中,传输的是随机数而不是信息,要再经过一次经典通信才能完成信息的传输.在量子信道直接传输信息的量子通信形式是量子安全直接通信.基于量子隐形传态的量子通信(简称量子隐形传态通信)是否属于量子安全直接通信尚需解释.构造了一个量子隐形传态通信方案,给出了具体的操作步骤.与一般的量子隐形传态不同,量子隐形传态通信所传输的量子态是计算基矢态,大大简化了贝尔基测量和单粒子操作.分析结果表明,量子隐形传态通信等价于包含了全用型量子密钥分发和经典通信的复合过程,不是量子安全直接通信,其传输受到中间介质和距离的影响,所以不比量子密钥分发更有优势.将该方案与量子密钥分发、量子安全直接通信和经典一次性便笺密码方案进行对比,通过几个通信参数的比较给出各个方案的特点,还特别讨论了各方案在空间量子通信方面的特点.     

量子密码通信中量子比特率理论分析

在量子密钥分配中,量子比特率是一个重要的系统参数。通过引入测量因子和筛选因子,建立了基于理想单光子源和泊松分布单光子源的量子比特率理论模型,给出了量子比特率的表达式,并对两种单光子源进行了比较分析。结果表明,当平均光子数大于1时,泊松分布单光子源能被优化。在发射机脉冲重复率一定的条件下,采用泊松分布单光子源无法达到理想单光子源的量子比特率,这是为保密通信所必须付出的代价。     

A full quantum network scheme

In this paper, we study the thermodynamic features of a two-dimensional charged black hole. Weinhold curvature and Ruppeiner curvature are explored as information geometry, respectively. Moreover, based on the Legendre invariant proposed by Hernando Quevedo, the geometro-thermodynamics behavior of this black hole is investigated.     

光纤色散与损耗对光量子密钥分发系统的影响

运用量子薛定谔方程,通过计算传输光场干涉强度和分析量子密钥分发系统的误码率,研究了光纤色散和损耗对量子密钥分发系统误码率的影响.研究表明,在目前的基于光纤的量子密钥分发系统中,选择色散位移光纤并以损耗最小波长1.55 μm为工作波长,同时缩短脉冲宽度,可以有效提高量子密钥系统的传输距离.关键词：量子保密通信量子密钥分发光纤色散光纤损耗