Theoretical Research On Quantum Cryptographic Protocols

Despite of the computational ability of the opponent, the security of quantum cryptographic protocols is only guaranteed by the fundamental principles of quantum mechanics. With more than 20 years of development, quantum cryptographic protocols have gradually developed into an important branch of cryptography. So far, various quantum cryptographic protocols, which have different important application backgrounds, have been presented in theory. Especially, some of them have been made great progress in experiment.The contributions of this dissertation are mainly on the cryptanalysis, design and security proof of quantum cryptographic protocols, including quantum key distribution, quantum secret sharing, message authentication and quantum anonymous transmission etc. The details are as follows:With respect to quantum key distribution, we analyze the security of a multi-user quantum key distribution protocol, and give a new attack strategy on the protocol by entangling an auxiliary qubit. Using the attack strategy, the opponent can gain access to the private key of any two legitimate users. We give a feasible improvement to resist the proposed attack strategy.With respect to quantum secret sharing, we analyze the security of two different multiparty quantum secret sharing schemes, and give a joint attack strategy on the two schemes. Using the joint attack strategy, two dishonest sharers, the first and the last, can gain access to the dealer's secret if they collaborate with each other. We give a general model for a kind of quantum secret sharing with single-particle states, and analyze the conditions that make it secure in the model, on the basis of which, we give a feasible way to design secure quantum secret sharing schemes in the model. With respect to quantum direct communication, we analyze the security of a multiparty controlled quantum secure direct communication protocol, and give a new attack strategy on the protocol by virtue of the idea of quantum teleportation. Using the attack strategy, the receiver can gain access to the sender's secret message without the permission of any controller. We also discuss how to improve the protocol to resist the proposed attack strategy. Furthermore, we propose a new multiparty controlled quantum secure direct communication protocol with phase encryption, and prove the security of the protocol.With respect to message authentication, we give a way to construct message authentication codes with single-particle states and decoherence-free states, respectively. We also prove the security of the proposed message authentication codes, and show that nobody can forge valid message authentication codes except with exponentially small probability.As for anonymous quantum transmission, we propose an anonymous quantum transmission protocol with an anonymous receiver, in which nobody can get any information on the identity of the receiver except the sender, and the privacy of the quantum information is perfectly protected. Furthermore, we propose a fully anonymous quantum transmission protocol, and it is more economical and efficient compared with the pioneering works.