Participant attack on a kind of MQSS schemes based on entanglement swapping.

A kind of multiparty quantum secret sharing (MQSS) schemes based on entanglement swapping is analyzed and an effective attack is proposed. Some unauthorized agent groups can recover the secret from the dealer with the help of this special attack. It is shown that entanglement swapping not only makes the MQSS protocols feasible but also brings a fatal drawback to them. Furthermore, a possible improvement on such protocols is proposed, which makes them secure against the proposed attack. [ABSTRACT FROM AUTHOR]