Based on EPR pairs, this paper proposes a different quantum private comparison (QPC) protocol enabling two parties to compare the equality of their information without revealing the information content. Due to the use of quantum entanglement of Bell state as well as one-way quantum transmission, the new protocol provides easier implementation as well as better qubit efficiency (near 50%) than the other QPCs. It is secure against Trojan horse attack and other well-known attacks.

New quantum private comparison protocol using EPR pairs

Two conditions must be satisfied in a secure quantum key agreement (QKA) protocol: (1) outside eavesdroppers cannot gain the generated key without introducing any error; (2) the generated key cannot be determined by any non-trivial subset of the participants. That is, a secure QKA protocol can not only prevent the outside attackers from stealing the key, but also resist the attack from inside participants, i.e. some dishonest participants determine the key alone by illegal means. How to resist participant attack is an aporia in the design of QKA protocols, especially the multi-party ones. In this paper we present the first secure multiparty QKA protocol against both outside and participant attacks. Further more, we have proved its security in detail.

Multiparty quantum key agreement with single particles

As an important branch of quantum cryptography, quantum private comparison (QPC) has recently received a lot of attention. In this paper we study the security of previous QPC protocols with a semi-honest third party (TP) from the viewpoint of secure multi-party computation and show that the assumption of a semi-honest TP is unreasonable. Without the unreasonable assumption of a semi-honest TP, one can easily find that the QPC protocol (Tseng et al. in Quantum Inf Process, 2011, doi: 10.1007/s11128-011-0251-0 ) has an obvious security flaw. Some suggestions about the design of QPC protocols are also given.

Comment on quantum private comparison protocols with a semi-honest third party

This paper proposes a pioneering quantum private comparison (QPC) protocol for n users. State-of-the-art QPC protocols have been designed for two users who wish to compare their private information. However, if n users want to perform the equality comparison, these two-user QPC protocols have to be executed repeatedly at least n ? 1 times. The proposed protocol allows n users' private information to be compared within one protocol execution. The proposed QPC protocol takes the Greenberger---Horne---Zeilinger (GHZ) class as a quantum resource and uses a special property in the GHZ-class state to perform the equality comparison. Moreover, due to the one-step quantum transmission, the protocol is free from Trojan horse attacks and it is also shown to be secure against other well-known attacks.

Multi-user private comparison protocol using GHZ class states

Two efficient quantum private comparison (QPC) protocols are proposed, employing single photons and collective detection. In the proposed protocols, two distrustful parties (Alice and Bob) compare the equivalence of information with the help of a semi-honest third party (TP). Utilizing collective detection, the cost of practical realization is reduced greatly. In the first protocol, TP gains the result of the comparison. While in the second protocol, TP cannot get the comparison result. In both of our protocols, Alice and Bob only need be equipped with unitary operation machines, such as phase plates. So Alice and Bob need not to have the expensive quantum devices, such as qubit generating machine, quantum memory machine and quantum measuring machine. Security of the protocols is ensured by theorems on quantum operation discrimination.

Efficient quantum private comparison employing single photons and collective detection

We propose a two-party quantum private comparison protocol using single photons, in which two distrustful parties can compare whether their secrets are equal with the help of a third party (TP). Any information about the values of their respective secrets will not be leaked out even with a compromised TP. Security is also discussed.

Secure quantum private comparison

Improved secure quantum sealed-bid auction

After analyzing the main quantum private comparison (QPC) protocols based on the entanglement states, we propose a new QPC protocol using only polarized single photons. It will be shown that entanglement is not necessary for QPC. Most importantly, it will be pointed out that QPC protocols can be constructed by adapting the current quantum three-party secret sharing models properly.

New quantum private comparison protocol without entanglement

We propose a (t, n)-threshold multiparty quantum-information splitting protocol following some ideas of the standard teleportation protocol [C. H. Bennett, G. Brassard, C. Crpeau, R. Jozsa, A. Peres and W. K. Wootters, Phys. Rev. Lett.70 (1993) 1895] and Tokunaga et al.'s protocol [Y. Tokunaga, T. Okamoto and N. Imoto, Phys. Rev. A71 (2005) 012314]. The sender distributes the classical shared keys to his or her n agents and each agent owns a secret key in advance. The sender's quantum information can be extracted by an agent subset by collaboration in such a way that at least t or more agents can get the quantum information with the mutual assistances but any t - 1 or fewer agents cannot. In contrast to the previous multiparty quantum-information splitting protocols in which the sender's quantum information can be recovered only if all the agents collaborate, our protocol is more practical and more flexible.

Threshold multiparty quantum-information splitting via quantum channel encryption

A quantum protocol for (t,n)-threshold identity authentication based on Greenberger-Horne-Zeilinger states is presented. A trusted third party (TTP) can authenticate the users simultaneously when and only when t or more users among n apply for authentication. Compared with the previous multiparty simultaneous quantum identity authentication (MSQIA) protocols, the proposed scheme is more flexible and suitable for practical applications.

Yu-Guang Yang

Papers

Secure quantum private comparison

Improved secure quantum sealed-bid auction

New quantum private comparison protocol without entanglement

Threshold multiparty quantum-information splitting via quantum channel encryption

A Quantum Protocol for (t,n)-Threshold Identity Authentication Based on Greenberger-Horne-Zeilinger States