差分量子保密通信系统的方案及稳定性研究

【作者】 陈霞；

【导师】 王发强；

【作者基本信息】 华南师范大学 ， 光学工程， 2007， 硕士

【摘要】 密码学是一门有着古老历史的应用科学。自古以来，它一直在军事、国防、外交等领域发挥着重要的作用。量子密码学是量子力学与密码学相结合的产物，差分量子编码是编码方案中应用性较强的一种方案，本文就是围绕差分量子保密通信系统展开的。第一章，介绍了量子密码学的基本概念和理论。包括：密码学的发展历程、基本概念；量子密码学的数学、物理基础。第二章，介绍了量子密钥的产生过程，并针对单光子协议进行了分析，依次详细介绍了BB84协议、B92协议和差分相位编码协议。其中详细介绍了差分相位编码协议的系统演化，包括：IWY方案、BLT／BLT⊕方案、双向来回式差分相位编码方案和自动补偿差分相位编码方案，同时引出了双协议方案。第三章，对量子保密通信系统的稳定性进行了分析。包括：以马赫曾德(MZ)干涉系统为例，分析影响系统稳定性的因素，对各种双折射机制、温度变化、机械振动、拉伸(压缩)、干涉仪的非对称性等影响做了分析；介绍提高系统稳定性的干涉仪：Sagnac干涉仪、法拉第反射式干涉仪和PLC干涉仪，其中详细介绍了法拉第反射式干涉仪提高稳定性的机理；最后针对差分量子保密系统，对其稳定性的保障和增强措施进行了简要分析。第四章，在BB84协议和差分协议的基础上首次提出一种新的密钥编码协议——双协议。该协议在继承差分协议优点的同时，克服了差分协议由于维度只有一维，在抵御截获——重发攻击时安全性存在的缺陷；在Bob端采用双法拉第旋转镜(FM)技术，完全补偿了Bob端的双折射现象和环境引起的偏振抖动，增强了系统的稳定性；采用分别评估不同测量基下误码率的安全性评估方法，进一步增强了系统的安全性。我们先后提出了双脉冲双协议方案和非对称多脉冲双协议方案：双脉冲双协议是在Alice端，用光纤MZ干涉仪产生双脉冲差分信号，同时大部分时间运行双脉冲二维调制差分协议和BB84协议，来弥补双脉冲的差分信号对截获／重发攻击存在安全漏洞。非对称多脉冲双协议使用多脉冲的光源，Alice和Bob分别以η(η→1)的概率选取{0，p}基中的相位，以(1-η)的概率选取{p／2，3p／2}基中的相位对脉冲信号进行调制。两维基的使用，加强了系统的安全性。以η(η→1)的概率选取{0，p}基中的相位对系统进行调制，相当于用差分协议进行编码，提高了系统的成码率。我们从理论和实验上依次论证了两种双协议方案的正确性和可行性，双协议是本文最主要的创新之处。更多还原

【Abstract】 Since ancient times, secret communications play a unique role in militaryand diplomacy. Cryptology is one of the technical tools for secretcommunications, where secrecy is based on the secrecy of keys. Quantumcryptography is a combination of quantum mechanics and cryptology. Thedifferential-phase-shift quantum key distribution scheme is one of the mostpromising schemes of quantum cryptography, which is the main content ofthis dissertation.In Chapter 1, the related principles and concepts of the quantum securitysystem are mainly introduced, including: the development and basic conceptsof cryptology.In Chapter 2, the related principles of the quantum key distribution aremainly introduced, including: the quantum key generation course and thesingle photon quantum key distribution schemes. We give the instruction ofBB84 scheme, B92 scheme and differential phase shift quantum keydistribution (DPS-QKD) scheme. The evolement of the DPS-QKD scheme isdiscussed in detail.In Chapter 3, the factors which influence the stability of the system arepresented, as well as the interference instruments which can enhance thestability of the system.In Chapter 4, a novel phase modulated quantum key distribution schemewith high security, which is combined DPS-QKD with BB84 scheme andcalled biprotocol of quantum cryptography, is proposed in this part. Thisscheme has several advantages: firstly, as we know, only {0,p} is used tomodulate the phase in DPS-QKD scheme, the degree of the freedom is one, soit is not security against intercept-and-resend attacks for this scheme. But inthe biprotocol of quantum cryptography, we use {0, p} and {p/2, 3p/2}together to modulate the phase of the pulses which makes the degree of thefreedom becomes two and thus enhance the security of the scheme. Secondly,in order to enhance the stability of the whole system, we use two MZinterferometers with Faraday-mirrors-based Michelson interferometers whichis used to compensate for birefringence and polarization-dependent losses inthe fiber in Bob’ site. Lastly, we evaluate the security in two different basesseparately to enhance the security of the system. We propose biprotocol ofquantum cryptography for two pulses and unsymmetrical biprotocol of quantum cryptography for multiple pulses.In biprotocol of quantum cryptography for two pulses, we use a fiber MZinterferemeter to generate the two pulse signals to encode information.DPS-QKD scheme which is used for most of the time and BB84 scheme areused together to enhance the security.In unsymmetrical biprotocol of quantum cryptography for multiplepulses, we use a coherent light source to generate pulses, select the phase tomodulate the pulses from {0, p} with the probability ofη(η→1) and selectthe phase to modulate the pulses from {p/2, 3p/2} with the probability of (1—η). By this way, the key generation rate and the security of the system areboth enhanced a lot.The biprotocol of quantum cryptography is the innovation of thisdissertation and experiments has been down to domenstrate the feasibility ofit.更多还原