Research On Data Reconciliation For Key Distribution In Quantum Cryptography Communication

With the rapid development of the information society,the traditional cryptography technology has been difficult to meet the requirements of modern communication systems.Quantum cryptography communication has become the new generation of communication cryptography technology which guarantees the efficiency and safety of information transmission.Quantum key distribution is an important branch of quantum cryptography system which uses the characteristics of quantum physics and classical cryptography technology to make the key distribution information impossible be decrypted.In the quantum cryptography system,data reconciliation is an important part and it guarantees the security in exchanging key both communication sides.In fact,data reconciliation is a technology which belong to the field of classic communication.It is the basic principle that makes use of channel coding to correct error information for key string,so that the communication are consistent with the data sequence between the two sides.Error correcting code adopt the low density parity check codes which are very close to the Shannon limit.It can greatly improve the efficiency of the communication system by its flexible encoding and decoding technology.The major work to the efficiency and security of data reconciliation technology are listed as following:The distribution of irregular LDPC code parity check matrix degree are optimized by using Gaussian approximated and analysis of the composition of the parity check matrix and different decoding scheme.It reduces the convergence signal to noise ratio,and make the foundation for the selection of error correcting code in the data reconciliation.This thesis proposes a specific data reconciliation of post-processing that the scheme is through the slice error correction protocol which uses the quasi-cyclic low density parity check code and traditional low density parity check code to cascade to compress and code.The receiver uses side information to decode processes.The variation of the security key quantity with different reconciliation is calculated on the continuous variable quantum key distribution with homodyne detection.To analyze the security of secret key extracted direct reconciliation and reverse reconciliation scheme are proposed in individual attack and collective attack,and the maximum transmission distance of the key is also estimated.Simulation results indicate that the data reconciliation efficiency can achieve 91.2%when code length is 2×10~5 and the third and fourth level code rate is 0.3/0.95.The amount of the extracted secret key can reach 9.46kb/s when Eve uses individual attacks.Meanwhile,the extracted secret key can reach 3.98kb/s when using the optimal attack and transmission distance can reach about 30km.The results prove the safety and effciency of the data reconciliation scheme and provided an important theoretic for the metropolitan area network using quantum cryptography communication.