Research On Several Problems Of Quan-Tum Secure Communication

Quantum secure communication technology is based on the basic principles of quantum mechanics,combined with information science and cryptography.As a new interdisciplinary,quantum secure communication technology can achieve information acquisition,transmission,processing and storage,which has made significant progress over the last three decades.With the development of society and advance of science and technology,information transmission and exchange become faster and faster nowadays,the demand for security and reliability of communication system is much higher than before.Different from the classical communication,the security of quantum communication depands on principles of quantum mechanics rather than computational complexity hypothesis,which security is guaranteed by Heisenberg uncertainty principle,nonorthogonal indistinguishable theorem and quantum non-cloning theorem.Quantum secure communication technology has unconditional security and detectability for an eavesdropper,these two features can not be achieved in the classical communication.Therefore,quantum secure communication technology has a huge advantage in the security and reliability of information trasmission.In this thesis,we study the related protocols of quantum secure communication.The main contributions of this thesis are as follows:1.In this thesis,we put forward a weak blind quantum signature protocol based on quantum entanglement swapping of Bell states.The protocol uses the symmetric cryptography to complete the signature and verification.Different from the existing quantum signature protocols,our protocol can offer two-step verification services to ensure the validity of the verification.The two-step verification process includes verification of the signature information and verification of the initial information.The protocol utilizes the entanglement swapping of Bell states principle as the foundation for signature and verification.The entanglement swapping of Bell states mechanism enhances the security of verification criteria.Besides,our protocol contains a trusted arbitrator,who is responsible for controlling the protocol process and verifying the authenticity of signature information and initial information.Futhermore,the proposed protocol has the properties of non-forgeability,non-repudiation,blindness and traceability.2.This work proposes two fault tolerant quantum blind signature protocols based on the entanglement swapping of logical Bell states,which are robust against two kinds of collective noises: the collective-dephasing noise and the collective-rotation noise,respectively.Both of the quantum blind signature protocols are constructed from four-qubit decoherence-free(DF)states,i.e.,logical Bell states.The logical states are served as the travelling states to combat the collective noise.Therefore,our protocols can offer the higher communication fidelity.The protocol utilizes the entanglement swapping of logical Bell states principle as the foundation for signature and verification.Based on the fundamental property of quantum entanglement swapping,the receiver just needs to perform two Bell-state measurements on the logical Bell qubits to verify the signature,which makes the protocols more convenient in a practical application.Moreover,we prove the security of the protocols against some individual eavesdropping attacks,and we show that our protocols have the inherent characteristics of quantum blind signature.3.Aiming at the limitations and security vulnerabilities in the WLS protocol,this thesis proposes an improved quantum multi-signature protocol based on the controlled quantum teleportation.The study found that the WLS protocol exists several problems.Firstly,it has been found that a particle of the GHZ state in the WLS protocol is not used in the signature and verification phases.The improved protocol utilizes the Bell state instead of the GHZ state as the information carrier.With the present techonology,the Bell state is easier to be implemented than the GHZ state.Secondly,the WLS protocol can only sign on certain specific information,so that the applicability of the WLS protocol receives restrictions.The improved protocol eliminates the restriction on the initial information parameters,which can sign on any quantum state.Finally,the security analysis shows that the WLS protocol can not prevent the attacks of the dishonest internal participant.The improved protocol can effectively overcome the security problems of the WLS protocol.4.In this thesis,we propose a semiquantum secure direct communication protocol with Einstein-Podolsky-Rosen(EPR)photon pairs in which classical sender Bob can transmit a secret message to quantum Alice directly.Therefore,the protocol can use less quantum resources to achieve the quantum secure direct comminication.The proposed protocol mainly contains two communication phases: the security checking phase and the message coding phase.After checking the security of quantum channels,Bob encodes his secret message on Alice's code qubits;Alice can extract Bob's secret message by measuring her home qubits and the returned code qubits,respectively.We demonstrate the security of the protocol against some individual eavesdropping attacks.Furthermore,the efficiency analysis shows that our protocol can provide higher efficiency.5.In this thesis,we incorporate the idea of DFS into semiquantum key distribution and propose two fault-tolerant semiquantum key distribution protocols,the randomization-based semiquantum key distribution protocol and the measure-resend semiquantum key distribution protocol,which are robust against the collective-dephasing noise.Logical qubits have been selected to build travelling blocks for constructing a decoherence-free subspace.Thus,our protocols can provide higher communication fidelity.In this protocol,Alice encodes each bit of the secret key in the logical qubit and sends logical qubits randomly to Bob;Bob randomly chooses his classical operations on these received logical qubits.Alice and Bob can create a shared key through this communication process.The security analysis proves that our protocol can resisit some individual attacks.