Study On Protocol And Security Strategy Of Quantum Communication

Quantum communication is developed by the needs of information security. Quantum mechanics and classical communication is the cornerstone of quantum communication. Quantum communication includes the quantum key distribution, quantum secure direct communication, quantum secret sharing, quantum identification and quantum teleportation etc.Quantum communication has attracted more and more interests for its unconditional security guaranteed by Heisenberg uncertainty principle and quantum no-cloning theory. The National Science Foundation and the United States Department of Defense is looking to this new technology. The European Union has started the research since 1999. Quantum communication also has been written into the ten-year plan of Japan. The importance of study quantum information technology, including quantum communication, has been improved to a high position in the issue of long-term science and technology development program (2006-2020) in China.Quantum communication will play a major role in the transmission of security information in national defense, banks, and confidential government department. This dissertation is focused on quantum key distribution protocol, eavesdropping strategy of quantum key distribution, decoy-state quantum key distribution and quantum secure direct communication with authentication. The main contributions of this work can be summarized as follows:The security of BB84 quantum key distribution protocol has been theoretical researched. A mathematical model has been founded based on information theory and quantum measurement channel. The amount of information and the quantum bit error rate caused by eavesdropper are analyzed while the BB84 quantum key distribution protocol is attacked by intercept/resend attack using different measurement bases. The formulation results showed that the quantum bit error rate threshold that legitimate user used to detect intercept/resend attack must be set properly, and the measurement result must be compared both Bob choose the right measurement basis and wrong measurement basis. A new standard is provided for the detection of eavesdropper.A new eavesdropping strategy based on Breidbart basis is proposed. Combined with BB84 quantum key distribution, its performance has been analyzed. Eve intercepts and keeps the photons Alice sends to Bob in the quantum memory. Then she randomly sends a sequence of photons polarized with Breidbart basis to Bob. If the quantum bit error rate caused by Eve is smaller than the threshold, Eve will not be discovered by Alice and Bob. When Alice and Bob communicate in public channel, Eve can know which basis is correct and measure the corresponding photons to get the key at 100%.A high performance decoy state for quantum key distribution is proposed. With modified coherent state, we can decrease the multi-photon in weak coherent source by canceling two or three photons to improve security distance of decoy state QKD. Based on the math model of decoy state, we deduced the formula of the yield and error rate of single photon with Modified Coherent State, and substituted in GLLP to calculate the generation rate of quantum keys. The formulation results showed that decoy state with Modified Coherent State can increase transmission length, and provide a theory basis to next step in practical application.A new quantum secure direct communication (QSDC) scheme with authentication is proposed, based on polarized photons and EPR pairs. EPR pairs are used to transmit information, while polarized photons are used to detect Eve and their measurement bases are used to transmit authentication information. Alice and Bob have their own identity number which is shared by legal users before communication. Identity number is encoded on the bases of polarized photons and distilled if there is no Eve. Compared with other QSDC with authentication, this new scheme is considerably easier and less expensive to implement in a practical setting.