| With the development of information technologies and the increasing of information exchange, it becomes more important for people to have a research on information security than ever before. quantum cryptography, which is based on conventional cryptography and quantum physics, has gotten more attention because of its significant advantages. According to modern cryptography, the security of encryption system is decided by the private level of key. Encryption and decryption algorithms in encryption system can be made known to public. As the focus of research, Quantum key distribution (QKD), which uses Heisenberg uncertainty relation and quantum no-cloning principle, not only ensures the absolute security of communication between sender and receiver, but makes the ability of detecting eavesdropper possible. However, considering the difficulty in single photon generation, detection and finding, the transmission rate achieved by QKD is low, especially based on discrete variables and free space. To improve the transmission rate of continuous variable, the following works are presented in this paper.1) Analysing the working process of QKD protocol. After coordinating the information, the initial key string can be achieved by both sender and receiver. In order to eliminate eavesdropping on the information included in the initial key string, more protections should be needed through the way of getting the secure key from the initial key. Because of the sensitivity of chaotic system caused by initial state and the good randomness of chaotic sequence, the chaotic system is introduced, after the initial key is randomly arranged into the chaotic system. Eavesdropper only gets a little part of information of the initial key string, so it will be impossible for him to get the same string that the sender and the receiver has.2) A specific plan is proposed. In this plan, the initial key string is randomly re-arranged and divided into blocks, its purpose is to set chaotic system. In order to get the final key string, the chaotic sequence needs to be digitized, the information the eavesdropper has obtained needs to be removed. In addition to that, the security of the scheme is discussed.3) The simulation results show that how sensitive the chaotic system is to initial conditions, how the different binarization in the chaotic sequence will influence binary sequence and how to use the random performance of the key sequence to select the appropriate program parameters. |
