  Recently, Liu et al. [Commun. Theor. Phys. 57, 583, 2012] proposed a quantum
private comparison protocol based on entanglement swapping of Bell states,
which aims to securely compare the equality of two participants' information
with the help of a semi-honest third party (TP). However, this study points out
there is a fatal loophole in this protocol, i.e., TP can obtain all of the two
participants secret inputs without being detected through making a specific
Bell-basis measurement. To fix the problem, a simple solution, which uses
one-time eavesdropper checking with decoy photons instead of twice eavesdropper
checking with Bell states, is demonstrated. Compared with the original
protocol, it also reduces the Bell states consumption and simplifies the steps
in the protocol.
