Design And Analysis Of Quantum Cryptographic Protocols

Quantum cryptography is a new cryptosystem which can realize the cipher by using quantum physics and gets a high level of attention.As an important branch in the field of information security,quantum cryptography is better superiority and greater safety than traditional classical cryptography.The security of classical cryptography is based on the assumption of computational complexity,while the security of quantum cryptography is guaranteed by the fundamental laws of quantum mechanics.Because quantum cryptography can provide unconditional security and has the ability of detecting eavesdropping behavior,it has very important strategic significance and tremendous prospect in applications.In addition,quantum cryptography has obtained significant achievements in both theory and experiments.The contributions of this dissertation are mainly on the design and security analysis of the protocols of quantum cryptography,including quantum key agreement,quantum secure direct communication,deterministic secure quantum communication and so on.The concrete content is as follows:A three-party quantum key agreement protocol is proposed based on single photons in both the polarization and the spatial-mode degrees of freedom.Three participants can effectively agree on a secure shared key by encoding their sub-secret bit strings on the single photons with collective unitary operations.Then the three-party quantum key agreement protocol is extended to the multi-party setting.The comprehensive analysis of security shows that our protocols are secure against both outside and participant attacks.Each participant in our quantum key agreement protocols contributes equally to the final shared key.The shared key cannot be determined by any non-trivial subset of participants and the sub-secret keys of the participants can be kept secret in the protocol.The efficiency analysis shows that our protocols are more efficient than previously proposed multi-party quantum key agreement protocols.Moreover,the proposed protocols are feasible since the preparation and the measurement of single-photon state in both polarization and spatial-mode degrees of freedom are available with current quantum techniques.Given that the most quantum secure direct communication protocols are based on the single photons with only one degree of freedom and entangled photons,a feasible three-party quantum secure direct communication is designed based on single photons in both the polarization and the spatial-mode degrees of freedom.The three legal participants' secret messages can be encoded on the polarization and the spatial-mode states of single photons independently with desired unitary operations.A party can obtain the other two parties' secret messages simultaneously through a quantum channel without any extra public information transmitted in the classical channels.Therefore,the security loophole of information leakage before eavesdropper detection is removed in the proposed protocol.Moreover,the comprehensive security analysis shows that the presented quantum secure direct communication network protocol can defend the outside eavesdropper's several sorts of attacks.Besides,the efficiency analysis shows that our protocol are more efficient than previously proposed three-party quantum secure direct communication protocols.A new controlled quantum secure direct communication protocol is proposed with single photons in both polarization and spatial-mode degrees of freedom.Based on the defined collective unitary operations,the sender's secret messages can be encoded directly on the single photons.Only with the permission and help of the controller,the receiver can reconstruct the secret messages accurately and successfully.Moreover,the security of the new protocol is discussed comprehensively.It is showed that the presented protocol can defend both the outside attacks and inside attacks.The external eavesdropper should not extract information about the transmitted secret messages and the receiver should not obtain secret messages without the permission of the controller.Compared with single photon in only one degree of freedom,the single photon in two degrees of freedom can improve the capacity of information transmission.Countering the security loophole that the information leakage before eavesdropper detection may exist in quantum secure direct communication,deterministic secure quantum communication scheme is presented.We design an efficient and authenticated bidirectional deterministic secure quantum communication scheme by using single photons in both the polarization and the spatial-mode degrees of freedom.After authenticating each other's identity,the two participants can encode their secret messages by performing different local unitary operations,which are chosen separately from the Pauli operations and Hadamard operations,on the single photons.A classic bit string is generated in the protocol.Two participants' secret messages can be only recovered accurately after the extra public information is transmitted in the classical channels.More importantly,the presented protocol can defend the outside eavesdropper's several sorts of attacks and the drawback of information leakage does not exist in it.Each single photon in two degrees of freedom can carry two bits of classical information.And the efficiency analysis shows that the presented protocol has a higher efficiency of information transmission.In addition,the proposed protocol only exploits the single photon,the preparation and the measurement of which is more feasible than that of hyperentangled state.So it is easy to implement with current experimental techniques.