Semi-quantum Key Agreement Protocols Based On χ-type Entanglement States And High-dimensional Quantum States

Quantum cryptography employs quantum states as information carriers to transmit keys between legitimate users through quantum channels.Because of its theoretical unconditional security and wide application prospects,the research field of quantum cryptography has developed rapidly in recent decades.Unlike classical cryptography,which is based on the computational complexity of unproven mathematical problems,some relevant technical schemes and theoretical systems in the field of quantum cryptography are not as mature as classical cryptography.It is particularly important for the practical application of quantum cryptography to continuously improve the cryptographic protocols such as key distribution,key agreement,authentication and signature in the professional field of quantum cryptography.Aiming at the quantum key agreement,one of the branches of quantum cryptography,this dissertation designs two efficient and secure semi-quantum key agreement protocols based on four-particle entangled states and high-dimensional single-particle states,respectively.The main research works in this dissertation are as follows:To improve the utilization efficiency of quantum entanglement resources and reduce the requirements on the quantum capabilities of participants,a new two-party semi-quantum key agreement protocol is proposed with four-particle χ-type entangled states.This protocol makes full use of the entanglement characteristics of the χ-type states and utilizes Bell measurements,Z-basis measurements,sequence permutation operations and single-particle quantum unitary operations to negotiate and generate the final shared key.The security analysis shows that the proposed protocol could resist both participant attacks and outsider attacks.Besides,compared with other similar two-party quantum key agreement protocols,the presented protocol possesses relatively high qubit efficiency(up to 42.11%)by utilizing the randomness of the collapse of quantum entangled states.There is only one participant possessing quantum capability in the protocol,which could reduce the requirement of quantum operation of quantum participants without involving the joint measurement capability of four qubits.To apply the excellent properties of the high-dimensional quantum system and the concept of semi-quantum into the quantum key agreement,a new efficient two-party semi-quantum key agreement protocol is proposed with high-dimensional single-particle states.Different from the previous semi-quantum key agreement protocols based on the two-level quantum system,the propounded protocol makes use of the advantage of the high-dimensional quantum system,which possesses higher efficiency and better robustness against eavesdropping.Besides,the protocol allows the classical participant to encode the secret key with qudit shifting operations without involving any quantum measurement abilities.The designed semi-quantum key agreement protocol could resist both participant attacks and outsider attacks.Meanwhile,the conjoint analysis of security and efficiency provides an appropriate choice for reference on the dimension of single-particle states and the number of decoy states.When the number of decoy states and the dimension of high-dimensional single-particle states in the transmission sequence are equal to 30 and 4,respectively,the proposed semi-quantum key agreement protocol could achieve acceptable efficiency and a high level of security.