Simple Collaboration Eavesdropping on the Improved Multiparty Quantum Secret Sharing Protocol

We propose a new attack strategy for the improvement n-party (n≥4) case S. Lin, F. Gao, Q.Y. Wen, F.C. Zhu in Opt. Commun. 281:4553, 2008] of the multiparty quantum secret sharing protocol Z.J. Zhang, G. Gao, X. Wang, L.F. Han, S.H. Shi in Opt. Commun. 269:418, 2007]. Our attack strategy is an interesting collaboration eavesdropping and much simpler than that in the paper T.Y. Wang, Q.Y. Wen, F. Gao, S. Lin, F.C. Zhu in Phys. Lett. A 373:65, 2008].