Quantum communication,a new communication technology which has been developed in recent years. Quantum communication is a new subject produced by the combination of quantum theory and information theory. Quantum communication has been proved to have absolute security communication mode in theory, while quantum key distribution is the most thorough study and the most widely used in the current quantum communication.The theory and actual quantum key distribution system also remain certain differences, such as the light detector efficiency is mismatching. These differences may be taken advantage by Eve to gain some or even all the key informations, thus the actual quantum key distribution system requires more strict safety analysis and argument, which is the focus in current researches.The paper emphatically introduces the security research under the efficiency mismatch attack in quantum key distribution system. This research mainly includes the following aspects.Firstly, we introduce the development of the quantum communication, the basic concept of quantum key distribution protocol, background knowledge, and related key technologies. And then it introduces the typical quantum key distribution protocol BB84 protocol and the B92 protocol, the paper used by the single-photon detector based on phase-encoding double MZ interferometer basics.Secondly, two types of attack models(pseudo state attacks and time shift attack) have been analyzed and discussed using the efficiency mismatching of two single photon detector in quantum key distribution system. Additionally, the two kinds of attack models have been carried on a thorough comparable analysis and research.pseudostate attack refers to the eavesdropper intercepted and perform a complete measurement to each quantum state emitted by the sender. Then based on her measurements a new shifted signal could been produced. In the case of detector efficiency mismatching, the eavesdropper can grasp part of the informations, without introducing any mistakes. Time-shift attack is that the Eve doesn’t measure the quantum state emitted by the sender. On the contrary, Eve just needs to put Alice’s signal forward or backward time shift simply according to her will.Third, the paper presents a scheme to overcome the time shifting attack, and improve the synchronization system. Using free-running mode of the ID210 single photon detector overcomes the time shifting attack. The ID210 operation allow internal gated, external gated,free-running or free-gating modes. Our former practical QKD system adopts APD of gate control signal.That is to say,only when the "door ’’open the signal is just rising and it count once.The article selects the free running mode(asynchronous mode), because in this mode we don’t need the door control and then overcome the attacks.Fourth,the synchronization of the information both sended and received is critical in quantum key distribution system. Only the information synchronized, the subsequent key could be extracted. In order to ensure the accuracy of the single photon counting, we need to send the synchronous signal of the sender to the receiver accurately, and synchronizing with the detected information of the single photon detector. If the accuracy of synchronization signal is higher and the error rate is bit lower, the single photon counting will be more accurate, the performance of quantum key distribution system also better. We use delay chip AD9501 in our laboratory. In this paper STM32 was used to control the two time delay chips DS1023-200 and MC100EP195, executing two levels of delay. We convert the original manual adjustment to automatically adjustment, and improve the efficiency. Moreover, the implementation solutions by hardware and software are raised. At last,we not only summarize the main contents of the paper,but also propose the next research direction that is primaily using quantum key distribution protocol of MDI to overcome the attack caused by receiver equipment imperfect and the research based on the sources ID equipment not perfect attack. |