Quantum private comparison protocol without a third party

TL;DR

This paper introduces a feasible quantum private comparison protocol that operates without a third party, achieving limited information leakage and advancing secure two-party quantum computations.

Contribution

It presents a novel quantum private comparison protocol that functions without a third party and quantifies the maximum information leakage involved.

Findings

Maximum information leakage is capped at 14 bits.

The protocol is feasible and efficient for practical use.

Leakage cannot be reduced to zero but remains bounded.

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.