In a recent paper [Z. J. Zhang and Z. X. Man, Phys. Rev. A 72, 022303 (2005)], a multiparty quantum secret sharing protocol based on entanglement swapping was presented. However, as we show, this protocol is insecure in the sense that an unauthorized agent group can recover the secret from the dealer. Hence we propose an improved version of this protocol which can stand against this kind of attack.

• Received 12 December 2006

DOI:https://doi.org/10.1103/PhysRevA.76.036301