Semiquantum Key Distribution And Agreement

With the rapid development of quantum cryptography,its popular research branches quantum key distribution and quantum key agreement have achieved rich fruits,and the security of information transmission has been greatly guaranteed.The ultimate purpose of quantum key distribution and quantum key agreement is to share a string of identical keys among all legitimate communication parties.The biggest difference between the two is that the former only requires one party to distribute her key to other parties through a quantum channel,that is,the key is determined by one party alone.The latter requires all participants to participate equally in the key generation process,and the shared key cannot be controlled by any non-trivial subset of all participants.In order to improve the practical applicability,the concept of "semiquantum" is put forward.The semiquantum involves the classical communicator,whose quantum ability is limited and can only do the following operations:(1)measuring qubits in the Z basis((?));(2)preparing new qubits in the Z basis;(3)sending qubits without disturbance;(4)arranging the order of qubits through different delay lines.This dissertation studies semiquantum key distribution and semiquantum key agreement,and proposes three innovative protocols specifically as follows:(1)A novel two-party semiquantum key distribution protocol based on GHZ-like states is proposed,which uses only one type of GHZ-like entanglement states as the initial quantum resources and realizes the generation of a secret shared private key between a quantum party and a classical party without a third party.The protocol does not require Hadamard gate or entanglement swapping,and is more efficient and flexible than several existing semiquantum key distribution protocols.(2)A single-state multi-party semiquantum key agreement protocol based on multi-particle GHZ entangled states is proposed.By using only one type of GHZ entangled states as the initial quantum resources,the goal of equally facilitating the generation of shared private keys between a quantum party and N-1classical parties on a quantum channel can be achieved.This protocol is more practical because it does not require the pre-sharing of keys between different participants,nor does it require the use of unitary operations or entanglement swapping.(3)A multiparty semiquantum key agreement protocol with d-level single-particle states is proposed.Using single particles as initial quantum resources,a quantum party and N-1classical parties can equally generate the final shared key through a quantum channel.Classical parties need to use quantum shift operations to encode their keys and perform quantum measurement operations.This protocol does not require the classical party to perform the permutation operation and is more extensible than the existing d-level semiquantum key agreement protocol.