Research On Quantum Cryptography Communication Network Design And Operation Mechanism

Quantum mechanics has unique advantages in processing classical information, and it combined with information science results in the physics of quantum information, which is an inevitable trend, so more and more scholars begin to study quantum communication. With the development of the internet, information security has become a problem which can not be ignored, and quantum cryptography is an integral part of this field. To achieve unconditional secure communication, we must rely on quantum cryptography. Secure Keys can be obtained through Quantum Key Distribution(QKD) between the two communication parts, which can be used by one-time-pad to ensure the security of classical communication. However, the quantum key rate generated by the QKD protocol is limited, which changes with the communication distance and transceiver. So it has become essential to use the quantum key reasonably in a practical multi-user communication network. We need to build a reasonable communication network based on quantum mechanics, with multiple nodes connected together through a certain network topology.Firstly, this thesis describes the differences between classical information and quantum information, and makes a brief narrative on the current development status, background and research progress of experimental quantum cryptography communication. Secondly, it introduces some basic knowledge of quantum cryptography, unique properties of quantum state as well as two important QKD protocols,known as BB84 and B92 protocol. Then, based on the characteristics of quantum cryptography, the quantum secure communication network is designed, respectively from the use of different switching devices interconnect the network, the optimal sub-distance in quantum communication network, the operation mode of quantum communication network and the key usage policies. Depending on the characteristics of the local area network and the core network, they are selected different design parameters, operating modes and key usage strategies. Then the characteristics of OPNET network simulation software are introduced, the OPNET models for different parts in quantum communication network such as the quantum router, quantum switch, trust relay are created. The quantum communication network with the designed topology is constructed, the different policies are simulated with variable parameters. This paper put forward the idea of backup relay to design the network. In the simulation, we compared theperformance of the Local Area Network with backup relay and without it, the result shows that with the backup relay, the loss rate can be decreased obviously. The optimal polling period is also obtained by the simulation result of different parameters. In the Core Network simulation, the loss rate can not be reduced obviously by increasing the number of the backup relay. The network Capacity is also got by the simulation result of different number of users. The simulation result shows the validity of the design.