Controlled quantum key agreement based on maximally three-qubit entangled states

In this paper, we propose a two-party and a three-party controlled quantum key agreement (QKA) protocols with three-qubit GHZ states and Bell measurements. Compared with previous protocols, the significant change of our schemes is that a supervisor is introduced for controlling the agreement process to improve the controllability. Moreover, our protocols ensure each communication participant contribute equally to the agreement keys, and all participants can negotiate the shared keys without exchanging classical bits between them. The performance analysis shows that our protocols can be immune to outsider and participant attack.

New quantum key agreement protocol with five-qubit Brown states

We propose a new two-party quantum key agreement (QKA) protocol using five-qubit Brown states. One-way quantum transmission can be realized by merging Brown states and decoy photons randomly. The security of this protocol is shown to resist the outsider attack and participant attack over the ideal channel. Some methods are also proposed to ensure its security in noisy and lossy quantum channel. Finally, we generalize it and propose a multi-party QKA protocol based on Brown states.

Participant attack and improving dynamic quantum secret sharing using d-dimensional GHZ state

In 2017, Qin and Dai [Quantum Inf. Process. 16, 64 (2017). https://doi.org/10.1007/s11128-017-1525-y ], proposed a dynamic quantum secret sharing (DQSS) scheme based on the d-dimensional state. However, as shown in this study, a malicious participant can reveal the secret key of other participants without being detected. Furthermore, this study identifies a security issue in Qin and Dai’s DQSS protocol pertaining to the honesty of a revoked participant. Without considering these security issues, the DQSS protocol could fail at providing secret-sharing function. Therefore, two improvements are proposed to circumvent these problems.

REEXAMINING THE SECURITY OF THE RECONSTRUCTION PHASE OF THE HILLERY-BUZĚK-BERTHIAUME QUANTUM SECRET-SHARING PROTOCOL

The participant attack is the most serious threat for quantum secret-sharing protocols. However, it is only during the transmission of quantum information carriers that attention is paid to this kind of attack in the existing quantum secret-sharing protocols. The security considerations of the secret reconstruction phase of quantum secret-sharing protocols against this kind of attack are neglected. We demonstrate our viewpoint by taking the scheme of Hillery, Buzěk, and Berthiaume (HBB) [Phys. Rev. A59 (1999) 18–29] as an example. By telling a lie in the reconstruction phase, a dishonest participant can easily attain the entire secret key instead of eavesdropping during the transmission awkwardly, whereas the honest one cannot judge whether the dishonest one tells the truth and the obtained secret random key is identical to what the secret distributor owns because of lack of verification mechanism in the HBB protocol. It is not difficult to find that almost all the quantum secret-sharing protocols have such disadvantages. Our viewpoint presented may be useful for the design of other similar protocols.