Su-Juan Qin

Novel multiparty quantum key agreement protocol with GHZ states

In many circumstances, a shared key is needed to realize secure communication. Based on quantum mechanics principles, quantum key agreement (QKA) is a good method to establish a shared key by every party’s fair participation. In this paper, we propose a novel three-party QKA protocol, which is designed by using Greenberger–Horne–Zeilinger (GHZ) states. To realize the protocol, the distributor of the GHZ states needs only one quantum communication with the other two parties, respectively, and everyone performs single-particle measurements simply. Then, we extend the three-party QKA protocol to arbitrary multiparty situation. At last, we discuss the security and fairness of the multiparty protocol. It shows that the new scheme is secure and fair to every participant.

Quantum private comparison against decoherence noise

In this paper, we propose a quantum private comparison scheme which can be used in decoherence noise scenario. With the combination of decoherence-free states and error-correcting code, it achieves a fault tolerant quantum private comparison to prevent collective decoherence noise and limited other decoherence noise. And the third party used in the protocol is not needed to be semi-honest.

Quantum secret sharing via local operations and classical communication

We investigate the distinguishability of orthogonal multipartite entangled states in d-qudit system by restricted local operations and classical communication. According to these properties, we propose a standard (2, n)-threshold quantum secret sharing scheme (called LOCC-QSS scheme), which solves the open question in [Rahaman et al., Phys. Rev. A, 91, 022330 (2015)]. On the other hand, we find that all the existing (k, n)-threshold LOCC-QSS schemes are imperfect (or “ramp”), i.e., unauthorized groups can obtain some information about the shared secret. Furthermore, we present a (3, 4)-threshold LOCC-QSS scheme which is close to perfect.

An arbitrated quantum signature scheme with fast signing and verifying

Existing arbitrated quantum signature (AQS) schemes are almost all based on the Leung quantum one-time pad (L-QOTP) algorithm. In these schemes, the receiver can achieve an existential forgery of the sender’s signatures under the known message attack, and the sender can successfully disavow any of her/his signatures by a simple attack. In this paper, a solution of solving the problems is given, through designing a new QOTP algorithm relying largely on inserting decoy states into fixed insertion positions. Furthermore, we present an AQS scheme with fast signing and verifying, which is based on the new QOTP algorithm. It is just using single particle states and is unconditional secure. To fulfill the functions of AQS schemes, our scheme needs a significantly lower computational costs than that required by other AQS schemes based on the L-QOTP algorithm.

Reexamination of arbitrated quantum signature: the impossible and the possible

As a new model for signing both quantum and classical messages, the arbitrated quantum signature (AQS) protocols have recently attracted a lot of attentions. In this paper, we analyze their security from an important security aspect—the receiver’s forgery of the signature, and provide a detailed proof of the fact that the attempt to design an improved optimal encryption used in AQS cannot prevent the receiver’s forgery attack unless some assistant security strategies are introduced. In order to show that, we firstly summarize an explicit formalization of the general AQS model and propose the necessary and sufficient conditions against the receiver’s forgery attack. Then a contradiction of them has been pointed out. In order to complete our security analysis, we verify that the AQS protocols for signing classic messages are still susceptible to the receiver’s forgery. Finally, some assistant security strategies are provided to recover the security.

Cheat sensitive quantum bit commitment via pre- and post-selected quantum states

Cheat sensitive quantum bit commitment is a most important and realizable quantum bit commitment (QBC) protocol. By taking advantage of quantum mechanism, it can achieve higher security than classical bit commitment. In this paper, we propose a QBC schemes based on pre- and post-selected quantum states. The analysis indicates that both of the two participants’ cheat strategies will be detected with non-zero probability. And the protocol can be implemented with today’s technology as a long-term quantum memory is not needed.

Comment on 'Two-way protocols for quantum cryptography with a nonmaximally entangled qubit pair'

Three protocols of quantum cryptography with a nonmaximally entangled qubit pair [Phys. Rev. A 80, 022323 (2009)] were recently proposed by Shimizu, Tamaki, and Fukasaka. The security of these protocols is based on the quantum-mechanical constraint for a state transformation between nonmaximally entangled states. However, we find that the second protocol is vulnerable under the correlation-elicitation attack. An eavesdropper can obtain the encoded bit M although she has no knowledge about the random bit R.

Local indistinguishability of orthogonal product states

In the general bipartite quantum system

A quantum secret-sharing protocol with fairness

m \otimes n

Practical quantum all-or-nothing oblivious transfer protocol

, Wang \emph{et al.} [Y.-L Wang \emph{et al.}, Phys. Rev. A \textbf{92}, 032313 (2015)] presented