Design And Analysis Of Multi-party Quantum Key Agreement Protocols Based On Continuous Variable

With the rapid development of quantum computing,classical cryptography that relies on mathematical problems and computational complexity is threatened.Quantum cryptography,which combines quantum mechanics and classical cryptography,came into being at the historic moment,and now has many branches,which has good research significance.Quantum cryptographic protocols can be divided into discrete variable protocols and continuous variable protocols according to the encoding information carrier.Compared with discrete-variable protocols,the preparation of continuous variable quantum states is less difficult,the protocol's ability to resist attacks is increased,the channel capacity is increased,and communication efficiency is improved.As an important research direction of quantum cryptography,quantum key agreement is more fair than quantum key distribution.It can negotiate a shared key without a third party.In view of the vacancy of quantum key agreement in the field of continuous variables and the shortcomings of the existing continuous variable quantum cryptography protocols,a multi-party quantum key agreement protocol is designed and analyzed based on three different continuous variable quantum states.There are mainly the following contents.(1)Using the continuous variable single-mode squeezed states to implement a three-party quantum key agreement protocol,encoding information on a regular component of the single-mode squeezed states.Each participant sends the quantum state of the encoded information to other participants in turn.By measuring the initial and the secretly encoded quantum state,the final key can be obtained at the same time.The protocol is highly efficient.In addition,the idea of extending the protocol to any number of communicating parties is proposed.The protocol performs random decoy operations in different time slots to detect eavesdropping in the channel,ensuring that confidential information is not leaked.Through the calculation of mutual information and secure code rate,it is found that the protocol performs well on Gaussian channels.(2)Implementation of a three-party quantum key agreement protocol using continuous variable two-mode squeezed states.Encryption and Bell-based measurements of the two-mode squeezed states can exchange secrets between the two parties.Any one participant can obtain the other two participants' secrets,so participants can negotiate the shared key.In addition,two kinds of multi-party quantum key agreement ideas based on two-mode squeezed states are proposed.Using the entanglement characteristic of the two-mode squeezed states,the channel can be subjected to bidirectional entanglement detection and eavesdropping detection.Security analysis can prove that the protocol can resist attacks from internal and external participants and eavesdroppers.The protocol can achieve higher security code rates in ideal channels and in the presence of beam splitting attacks.(3)Using continuous variable GHZ states to realize multi-party quantum key agreement protocol.Using the characteristics of the prepared triple GHZ state to encode the amplitude components,combining classical cryptography and quantum cryptography,multi-party quantum key negotiation is achieved under the premise of minimizing the leakage of secret information.Utilizing the entanglement characteristics of continuous variable GHZ states,the channel are subjected to bidirectional entanglement detection and wiretapping detection.Security analysis shows that the proposed protocol can resist multiple attack methods.From the perspective of information theory,it proves that the protocol can resist joint eavesdropping and achieve unconditional security.