Ke-Jia Zhang

Cryptanalysis and improvement of the quantum private comparison protocol with semi-honest third party

Recently, a quantum private comparison (QPC) protocol with a dishonest third party (TP) (Yang et al. in Quantum Inf Process, 2012. doi:10.1007/s11128-012-0433-4) was proposed, which pointed out that the assumption of semi-honest third party (TP) is unreasonable. Here we find this protocol is not so secure as it was expected, and then we give some improvement strategies, which ensure that both players’ secrets will not be leaked to anyone. We also discuss the assumption for TP in QPC protocls, which gives a constructive suggestions for the design of a new QPC protocol.

Improving the security of arbitrated quantum signature against the forgery attack

As a feasible model for signing quantum messages, some cryptanalysis and improvement of arbitrated quantum signature (AQS) have received a great deal of attentions in recent years. However, in this paper we find the previous improvement is not suitable implemented in some typical AQS protocols in the sense that the receiver, Bob, can forge a valid signature under known message attack. We describe the forgery strategy and present some corresponding improved strategies to stand against the forgery attack by modifying the encryption algorithm, an important part of AQS. These works preserve the merits of AQS and lead some potential improvements of the security in quantum signature or other cryptography problems.

Security analysis of quantum multi-signature protocol based on teleportation

The security of the recent quantum multi-signature protocol based on teleportation is analyzed. We show that there are some security vulnerabilities in the protocol. The detailed attack strategies are described from the aspect of participant attack. We also point out that the protocol is not secure against external attack. Finally, we give some possible countermeasures to improve the protocol.

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.

A quantum protocol for millionaire problem with Bell states

We propose a quantum protocol for the millionaire problem with Bell states, where two distrustful parties can compare the values of their fortune with the help of a semi-dishonest third party. The efficiency of our protocol is higher than that of previous protocols for millionaire problem. In our protocol, any information about the values of their fortune will not be leaked out. The security of our protocol is also discussed.

A novel quantum group signature scheme without using entangled states

In this paper, we propose a novel quantum group signature scheme. It can make the signer sign a message on behalf of the group without the help of group manager (the arbitrator), which is different from the previous schemes. In addition, a signature can be verified again when its signer disavows she has ever generated it. We analyze the validity and the security of the proposed signature scheme. Moreover, we discuss the advantages and the disadvantages of the new scheme and the existing ones. The results show that our scheme satisfies all the characteristics of a group signature and has more advantages than the previous ones. Like its classic counterpart, our scheme can be used in many application scenarios, such as e-government and e-business.

Quantum Walks on Two Kinds of Two-Dimensional Models

In this paper, we numerically study quantum walks on two kinds of two-dimensional graphs: cylindrical strip and Mobius strip. The two kinds of graphs are typical two-dimensional topological graph. We study the crossing property of quantum walks on these two models. Also, we study its dependence on the initial state, size of the model. At the same time, we compare the quantum walk and classical walk on these two models to discuss the difference of quantum walk and classical walk.