Research On Quantum Group Key Agreement Protocols

Since the first quantum key distribution(QKD)protocol was proposed by Bennett and Brassard,quantum cryptography communication technology has stepped gradually into the view of the public.Different from the classical key distribution(KD)protocols,the security of quantum key distribution protocols are guaranteed by the basic hypotheses of quantum mechanics,instead of the traditional computational complexity problems.Thus,it has been drawn wide attention from researchers over the world.Through about thirty years of development,the quantum cryptography communication technology based on QKD protocols has approached commercial market.Nevertheless,there are still many practical problems in today's quantum cryptography communication systems.For example,traditional QKD protocols are suitable only for the point-to-point communication model.However,applications involved multi-party in a typical communication network are very prevailing.Therefore,in order to build a large-scale QKD network,the problem about multiparty communication must be resolved.In addition,the traditional QKD protocols does not care about the question of identity authentication,and simply assume both parties in communication are legitimate,which is usually unrealistic in most communication networks.Moreover,although QKD can guarantee the unconditional security of key in theory,it may also exists many security breaches in practice,since the practical QKD systems are not absolutely perfect,such as non-ideal light source,channel noise,and detection flaw,and so on.To close the gap between theory and practice,researchers come up with different resolutions.For example,by the method of decoy states,it can make QKD free from the photon-number-splitting attack caused by non-ideal single photon source.By information reconciliation and privacy amplification,it can make QKD very robust in noisy channels.In 2012,Canadian researcher Lo et.al.put forward the measurement-device-independent quantum key distribution(MDI-QKD)protocol,which can close all security loopholes aiming at detectors once for all.Meanwhile,it has nice practical value and can be demonstrated easily in experiments.More importantly,MDI-QKD protocol can be easily extended to the multi-party situation,which naturally would be a huge advantage in QKD network.In view of those,it has been researched widely and deeply in recent years.In this dissertation,we focus on the basic MDI-QKD protocol and systematically study the multi-party group key agreement in QKD network and obtain some useful achievements:1.We study the traditional QKD protocols systematically and then we propose an identity authentication(IA)scheme applicable to MDI-QKD protocol,which can combine key distribution and identity authentication so that it can realize both of them effectively at a time,this characteristic is also one of main research interests in quantum identity authentication(QIA)protocols.Meanwhile,identity authentication is also very important in group key agreement protocols.Apparently,if the identity of members in group cannot be authenticated explicitly,then the secure group communication can not be guaranteed anymore.By pre-sharing a random password,we propose a novel scheme that combines the property of MDI-QKD protocol.Our scheme can easily and effectively accomplish identity authentication in MDI-QKD protocol.2.We study the group communication in today's QKD network and then we propose two kinds of measurement-device-independent quantum group key agreement(MDI-QGKA)protocols.Compared with the classical group key agreement protocol,our new protocols can make sure that group members negotiate an identical group key securely even in the case where the measurement devices in network are completely untrusted.The first protocol is based on the well-studied MDI-QKD,therefore,it possesses good applicability in nowadays.While the second one can accomplish the distributed group key agreement and it has a significant improve in the efficiency of key agreement,in this protocol it requires plenty of quantum operations,which means it may not apply into practices in a short time.3.We study the practical problems in quantum group key agreement protocols and then we improve the group key service model that in today's QKD network and propose a more suitable QKD network model for MDI-QKD protocol.Based on it,we optimize our first MDI-QGKA protocol deeply and comprehensively.About group member's leaving and joining,the communication rounds in group key agreement,the number of identity authentication between members,and the broadcast mode of group key,we come up with different ways of improvements.Meanwhile,we analyze two proposed protocols in depth.By utilizing the universally composable security model,we analyze our first protocol in detail.While from the perspective of entanglement,we give a meticulous survey on the security of the second protocol.