An efficient protocol for the quantum private comparison of equality with W state

We propose an efficient quantum protocol for comparing the equal information with the help of a semi-honest third party (TP). Our protocol utilizes the triplet W states and the single-particle measurement. A precise proof of security of the protocol is presented. The security of this protocol with respect to various kinds of outside attacks is discussed. Outside eavesdroppers cannot learn any information about the private information. The security of this protocol with respect to various kinds of party attacks is also discussed. One party cannot learn any information about the other's private information. The TP cannot learn any information about the private information, even about the comparison result or the length of secret inputs. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.