The Development Of Key Instruments And The Research On Attack And Defence In Quantum Secure Communication

Quantum key distribution(QKD), as the core of quantum secure communication,based on the fundamental principles of quantum mechanics, can in principle offer the unconditionally secure private communications between two users, Alice and Bob. The last three decades have witnessed dramatic advances in both theoretical and experimental developments of QKD, which is bringing quantum secure communication into practical applications. However, the key instruments and the security of quantum secure communication can not meet the need of practical applications in some aspects today. On the one hand, key instruments, such as single-photon detector(SPD)and weak-coherent-pulse laser, are imperfect, violating some of the assumptions in security proof. On the other hand, any imperfections in a practical QKD system may be exploited by an eavesdropper(Eve) to collect information about the key without being discovered. In this dissertation,we study the characteristic of key instruments and the research on attack and defence in quantum secure communication, and then the main results are listed as follows:1. We study high speed single photon detector based on In Ga As/In P-APD. We have finished 200 MHz repetition rate high speed SPD based on sinusoidal gating schemes in 2011, in which the In Ga As/In P-APD was cooled to-35?C. With detection efficiency of 10.6%,we have achieved a dark count rate of 3.95 × 10-5/pulse and an afterpulse probability of 6.26%. Then high speed SPDs with gating frequency up to 1GHz based on both of the sinusoidal gating schemes and the self-differencing technique have also been tested. Furthermore, in order to improve the stability, we proposed an innovative scheme for achieving high speed In Ga As SPD.2. We also study on the pulse laser used as weak-coherent-pulse in the quantum secure communication. On the one hand, we designed high speed narrow width pulse laser for BB84 QKD systems, which also can be used for high speed SPD research and quantum attack and defence research. On the other hand, we designed pulse lasers with identical wave shape and spectrum, which can be used in measurement device independent quantum key distribution(MDI-QKD).3. The decoy-state method has been widely used to be against the photon-numbersplitting(PNS) attack. However, decoy-state method itself may introduce anotherloophole while it has closed the loophole of multi-photon pulses. As is well known,decoy-state method is demonstrated based on the assumption that Eve can never distinguish the decoy state and the signal state. Unfortunately, this assumption is invalid in certain conditions, and Eve can beat the decoy-state method due to the property of intensity modulator. In this paper, we first demonstrate that Eve can distinguish the decoy state and the signal state in certain conditions, in which the intensity modulator used for the decoy-state method deviates from the model in the security proofs. Then a fatal loophole of decoy state ``plug-and-play" QKD systems has been exploited and a wavelength-selected PNS(WSPNS) attack scheme against``plug-and-play" QKD systems based on weak laser pulses is proposed. The results show that Eve can get information without being discovered by the legitimate parties, just like PNS attack was performed in ``plug-and-play" QKD systems without decoy-state method. In other words, under the WSPNS attack, decoy-state method in these systems is invalid, since it introduces another loophole while it has closed the loophole of multi-photon pulses.4. In order not to be discovered, the quantum bit error rate(QBER) introduced by Eve in an attack should be undetectable, since it is always used to estimate the amount of information eavesdropped by Eve in the channel. In this paper, we propose a frequency shift(FS) attack on ``plug-and-play" QKD systems with phase-coding BB84 protocol. In this attack, Eve also performs time shift on the signal pulse from the constant acting range of the phase modulation voltage to its rising edge to introduce an imperfection, just the same as what she does in the phase-remapping attack.But instead of phase-remapping, the imperfection to be considered in this paper, is frequency shift due to the working principle of phase modulator. The most novel advantage of our FS attack is that Eve can get full information without introducing detectable QBER.5. High-speed self-differencing(SD-) SPDs have been widely investigated and have been applied to QKD with Mbits/s secure key rate, high quality random numbers generation, and long distance entanglement distribution. However, the application of SD-SPD will be compromised by its loopholes. In this thesis, we analyze and demonstrate experimentally an intrinsic imperfection of SD-SPDs, which is introduced by its operation principle. Then we show that when this loophole is exploitedby Eve, the GHz high-speed QKD system can be fully remotely controlled. Thus it can be applied to attack the GHz high-speed QKD system, in which Eve blind the SD-SPDs by using bright blinding light pulses, and then she can fully remotely control the measurement results of Bob by sending a control light pulse superimposed over the bright blinding light pulse. Here we remark that the base of our attack lies in the operation principle of the SD-SPD, thus it can not be removed by modifying the SD-SPD, excepting some active countermeasures are applied by the legitimate parties.