The Research Of Information Reconciliation And Privacy Amplification In Quantum Key Distribution

Information security is a very significant issue. Cryptography is one of the efficient methods that protects the secret information from being eavesdropped. The conventional mathematical cryptography is based on the unproved computational assumptions. However, with the development of computer science and the breakthrough of the quantum computer, the information security mechanism depending on the conventional mathematical cryptography will face the challenges. Quantum cryptography is based on both the conventional cryptography and quantum physics. Its security is guaranteed by the fundamental laws of physics. Both quantum no-cloning the Heisenberg uncertainty relation ensure the absolute security and the ability of detecting eavesdropper. These facts guarantee that quantum cryptography has the excellent capacity and the attractive foreground.As an important research issue of quantum cryptography, quantum key distribution(QKD) is the most promising quantum information technology. However, due to the difficulty in both single photon generation and detection, the transmission rate of discrete variable QKD and quantum secure direct communication is very low. At present, the continuous variable quantum key distribution only can distribute the random key, can not securely transmit the secret message. So the continuous variable deterministic quantum secure communication is an interesting issue. In addition, almost all QKD schemes assume that the sender and the receiver are all the legitimate communicator, hardly considering the identification problem. Now, quantum identification has attracted many researchers'interest.To improve the transmission rate of continuous variable QKD and quantum secure direct communication, the following works are presented in this paper.1. Design a judgement function and a way to partition the interval to improve the efficiency of the information reconciliation phase of the QKD. The efficiency of reconciliation in the continuous key distribution is the main factor which limits the ratio of secret key distribution. However, the efficiency depends on the computational complexity of the algorithm. The paper optimizes the two main aspect of the reconciliation process of the continuous key distribution: the partition of interval and the estimation of bit. We use Gaussian Approximation to effectively speed up the convergence of algorithm. We design the Estimation Function as the estimator of the SEC (Sliced Error Correction) algorithm. So we lower the computational complexity and simplify the core problem of the reconciliation algorithm. Thus we increase the efficiency of the reconciliation process in the continuous key distribution and then the ratio of the secret key distribution is also increased.2. The key reconciliation plays important roles in the quantum key distribution as well as shared bit strings for final key distillation. To distill efficiently the final key a so-called `Winnow' algorithm has been proposed. However, how to choose the interval length of the shared string is very difficult even impossible in practical program processing. This leads the key ratio of the Winnow algorithm is very low, consequently, the `Winnow' algorithm can not be employed in application. In this paper we investigate analytically the dependence of the interval length on error distribution and code. Then an auto-adaptive interval selection algorithm is proposed via formulating the interval length. In addition, some new characteristics of the protocol are investigated.3. Design a software system to implement information reconciliation and privacy amplification algorithm. This is very instructive in engineering project.