We analyzed the security of the multiparty quantum secret sharing (MQSS) protocol recently proposed by Zhang, Li, and Man [Phys. Rev. A 71, 044301 (2005)] and found that this protocol is secure for any other eavesdropper except for the agent Bob who prepares the quantum signals as he can attack the quantum communication with a Trojan horse. That is, Bob replaces the single-photon signal with a multiphoton one and the other agent Charlie cannot find this cheating as she does not measure the photons before they run back from the boss Alice, which reveals that this MQSS protocol is not secure for Bob. Finally, we present a possible improvement of the MQSS protocol security with two single-photon measurements and four unitary operations.

https://arxiv.org/pdf/quant-ph/0506194.pdf

Improving the security of multiparty quantum secret sharing against Trojan horse attack

Multi-step quantum secure direct communication using multi-particle Green–Horne–Zeilinger state

We propose a theoretical scheme for secure quantum key distribution network following the ideas in quantum dense coding. In this scheme, the server of the network provides the service for preparing and measuring the Bell states, and the users encode the states with local unitary operations. For preventing the server from eavesdropping, we design a decoy when the particle is transmitted between the users. The scheme has high capacity as one particle carries two bits of information and its efficiency for qubits approaches 100%. Moreover, it is unnecessary for the users to store the quantum states, which makes this scheme more convenient in applications than others.

https://iopscience.iop.org/article/10.1088/0256-307X/22/5/006/pdf

Secure Quantum Key Distribution Network with Bell States and Local Unitary Operations

https://arxiv.org/pdf/quant-ph/0504119.pdf

Bidirectional quantum secret sharing and secret splitting with polarized single photons

Quantum secure direct communication is the direct communication of secret messages without need for establishing a shared secret key first. In the existing schemes, quantum secure direct communication is possible only when both parties are quantum. In this paper, we construct a three-step semiquantum secure direct communication (SQSDC) protocol based on single photon sources in which the sender Alice is classical. In a semiquantum protocol, a person is termed classical if he (she) can measure, prepare and send quantum states only with the fixed orthogonal quantum basis{|0>,|1>}. The security of the proposed SQSDC protocol is guaranteed by the complete robustness of semiquantum key distribution protocols and the unconditional security of classical one-time pad encryption. Therefore, the proposed SQSDC protocol is also completely robust. Complete robustness indicates that nonzero information acquired by an eavesdropper Eve on the secret message implies the nonzero probability that the legitimate participants can find errors on the bits tested by this protocol. In the proposed protocol, we suggest a method to check Eves disturbing in the doves returning phase such that Alice does not need to announce publicly any position or their coded bits value after the photons transmission is completed. Moreover, the proposed SQSDC protocol can be implemented with the existing techniques. Compared with many quantum secure direct communication protocols, the proposed SQSDC protocol has two merits: firstly the sender only needs classical capabilities; secondly to check Eves disturbing after the transmission of quantum states, no additional classical information is needed.

Three-step semiquantum secure direct communication protocol

Improving Wojcik's eavesdropping attack on the ping-pong protocol

In this paper, by introducing the additional classical information and taking advantage of the property of quantum entanglement swapping of two photon pairs instead of the property of quantum entanglement of a photon pair, the Bostrom-Felbinger protocol [Phys. Rev. Lett. 89, 187902 (2002)] is improved. In the improved protocol, when the photon travels from the message receiver's site to the message sender's site, any attack can be detected in the control mode. Moreover, it is deterministically successful to transmit the secret messages in the message mode. The security of the present improved protocol against the eavesdropping is ensured by the Bostrom-Felbinger protocol, and besides, the attacks proposed by Cai [Phys. Rev. Lett. 90, 109801 (2003)] to attack the Bostrom-Felbinger protocol without eavesdropping can be prevented.

Yong Li

Papers

Improving Wojcik's eavesdropping attack on the ping-pong protocol

The improved Bostrom-Felbinger protocol against attacks without eavesdropping

Improved Wójcik's eavesdropping attack on ping-pong protocol without eavesdropping-induced channel loss