Semi-quantum key distribution with two classical users

Abstract

Semi-quantum key distribution (SQKD) is an important research issue which allows one quantum participant equipped with advanced quantum devices to distribute a shared secret key securely with one classical user who has restricted capabilities. In this paper, we propose a SQKD protocol which allows one quantum user to distribute two different private secret keys to two classical users respectively at the same time. Alice distributes two particle sequences from Bell states to Bob and Charlie respectively. Once the particles have been processed and returned, Alice can simultaneously detect reflected particles by Bob and Charlie based on Bell-state measurement and generate two different raw keys. To enable more participants in sharing keys, this protocol can be extended to the m + 1 party communication scheme by employing m-particle GHZ state. In large-scale communication networks, this extended model significantly reduces the complexity of communication compared to the traditional SQKD scheme. Security analyses show that the presented protocol is free from several general attacks, such as the entangle-measure attack, the modification attack, the double CNOT attack, and so on.

A novel semiquantum key distribution protocol with Bell states

“…Hence, In addition, the comparison of this protocol and present SQKD protocols using Bell states without a third party [8,9,11] are made. The comparison results are shown in Table 2 for clarity.…”

“…It is apparent from Table 2 that compared with the SQKD protocols in Refs. [8,9,11], this protocol has the highest qubit efficiency and has the merit that the reflecting operations of the classical user contribute to the generation of final shared key.…”

“…This protocol is proven to be secure against various attacks from Eve. Compared with present SQKD protocols using Bell states without a third party [8,9,11], this protocol has two merits: (1) it has the highest qubit efficiency; and (2) the reflecting operations of the classical user contribute to the generation of final shared key. The protocol of Ref.…”

“…In this paper, a novel Bell states based SQKD scheme is designed, where the reflection operations of the classical user contribute to the generation of secret key. Compared with present SQKD protocols using Bell states without a third party [8,9,11], this protocol has the highest qubit efficiency.…”

“…Subsequently, Ye et al [6,7] utilized single photons in both polarization and spatial-mode degrees of freedom to design two novel SQKD schemes. Besides single photons based SQKD [1][2][3][4][5][6][7], numerous Bell states based SQKD schemes [8][9][10][11] have also been designed. However, in Bell states based SQKD schemes [8][9][10][11], the reflection operations of the classical user cannot contribute to the generation of secret key, which may decrease the qubit efficiency of communication.…”