Quantum private comparison protocol without a third party

Abstract

To evade the well-known impossibility of unconditionally secure quantum two-party computations, previous quantum private comparison protocols have to adopt a third party. Here we study how far we can go with two parties only. We propose a very feasible and efficient protocol. Intriguingly, although the average amount of information leaked cannot be made arbitrarily small, we find that it never exceeds 14 bits for any length of the bit-string being compared.Comment: 4 pages, 1 figur

Cryptanalysis and improvement of Wu-Cai-Wu-Zhang's quantum private comparison protocol

“…It is not considered as a "loophole" even if the external party Eve can cheat in these protocols. This is also the case of our previous QPC protocol in [5]. Nevertheless, it is surely an appealing improvement * Electronic address: hegp@mail.sysu.edu.cn if external eavesdropping can be defeated too.…”

“…Therefore, most existing quantum private comparison (QPC) protocols added a third party to accomplish the task (see [4] and the references therein). In 2016, we proposed a QPC protocol [5] which involves two parties only. Although it is not unconditionally secure, the loose upper bound of the average amount of information leaked is 14 bits only.…”

“…Recently, Wu, Cai, Wu and Zhang [12] reported the above problem of the protocol in [5], and they also proposed a new one (called as WCWZ protocol thereafter) aiming to achieve security against external eavesdropping. They also stated that the protocol in [5] has a second problem that "the result of comparison can be manipulated partially by either party", and "He's original protocol is not suitable for a smaller bit-length comparison protocol".…”

“…Recently, Wu, Cai, Wu and Zhang [12] reported the above problem of the protocol in [5], and they also proposed a new one (called as WCWZ protocol thereafter) aiming to achieve security against external eavesdropping. They also stated that the protocol in [5] has a second problem that "the result of comparison can be manipulated partially by either party", and "He's original protocol is not suitable for a smaller bit-length comparison protocol". We would like to note that in [5], it was already elaborated that 14 bits is merely the loose upper bound of the average amount of information leaked, and no cheating strategy has been found that can saturate this bound.…”

Multi-Party Quantum Summation Based on Quantum Teleportation

“…In quantum summation protocols, the privacy of participants’ inputs is preserved and the correctness of the summation is guaranteed by quantum properties. Quantum summation has also potential applications in quantum voting [ 17 , 18 , 19 , 20 , 21 ] and quantum private equality comparison [ 22 , 23 , 24 ]. Designing quantum summation protocols that can be implemented with current or near future quantum technologies is therefore of interest, as we pursue in this paper.…”