Protocols And Mechanisms In The Quantum Key Distribution Networks

Quantum key distribution (QKD), based on the laws of quantum physics rather than the mathematical computational complexity, can distribute key between two distant entities Alice and Bob, with the unconditional security, which brings security of cryptography into a higher level. The rapid progress in theory and experiment of QKD techniques has been reflected by a number of successful demonstrations in the last few years, including both the high key generation rate and long transmission distance. Many groups all over the world have put forward QKD setups operating in the standard point-to-point modus, some of which are already commercial available.To fulfill the requirements of multiple users' secure communications, QKD network becomes the trend towards distributing the secret keys on many-to-many nodes over potentially unlimited distances in the near future. Work toward the QKD network which supports multi-user, high rate and long distance with compatibility and robustness will allow QKD to achieve widespread usage in practical environments. Though many schemes of QKD networks have been presented, a systematic theoretic research is still absent. This paper studies the characteristics of QKD network, trying to propose protocols and mechanisms on various networks. The main contents include:1. According to the construction principle, three main types of QKD networks are discussed, which are trusted-relay based QKD network (TRN-QKD), passive-optical-element based QKD network (PON-QKD), quantum entanglement based QKD network (QEN-QKD),2. TRN-QKD can conveniently adopt many different point-to-point QKD schemes with low cost. However TRN-QKD may have security loophole when some trusted nodes become untrusted due to Eve's attack. In chapter 3, based on our safe probability model, we propose the multi-path secrecy sharing and stochastic routing scheme to avoid this problem with probability close to 1. Similar to the classical one, we utilize the queuing model to analyze the key delay, and propose a pre-buffer strategy to improve the delay performance, hence the Quality of Service (QoS) on TRN-QKD. Finally, the classical network coding can be seamlessly applied to TRN-QKD in the case of multi-user key sharing.3. Various PON-QKDs are introduced, which are constructed by beam-splitter, optical-switch and wavelength divided multiplexer (WDM) etc. We firstly set up the concepts of network capacity and connectivity on behalf of PON-QKD's performance. On the other hand, network cost including end user's cost and routing cost can reflects the economic feature of PON-QKD. Combining these two parameters, we can get the performance price ratio to describe PON-QKD synthetically. The comparison results of five PON-QKDs are given in chapter 4.4. QEN-QKD is consist of many nodes with the identical pure entanglement state between two adjacent nodes. What we focus on is the conversion probability of a general entanglement into the perfect entanglement, or singlet conversion probability (SCP). Based on the one repeater's result, we deduce the 1-dimentional chain strategy. In the case of small size of 2-d QEN-QKD, we may use multi-path scheme to increase SCP. While in the case of large size, no matter what distance, SCP mainly equals to the percolation probability's square using percolation theory. Finally we also propose asymptotic and anisotropic percolation effect.5. We study the compatibility between QKD and classical optical communication network in chapter 2, by analyzing the classical noise's influence to QBER. To apply QKD in Virtual Private Network (VPN), we give two demonstrations on PPP channel and IPSec protocol respectively.6. Finally in chapter 6, we present the idea of backbone and access networks. The QKD network layer model is also described in detail, which contains quantum link layer, quantum network layer, key extraction layer and key management layer. This architecture can be used in further QKD networks' research and implementations.