Multiparty quantum secret sharing of secure direct communication

Based on the two-step protocol [F.G. Deng, G.L. Long, X.S. Liu, Phys. Rev. A 68 (2003) 042317], we propose a (n,n)-threshold multiparty quantum secret sharing protocol of secure direct communication. In our protocol, the sender's secure direct communication message can be extracted only if all the sharers collaborate. We show a variant version of this protocol based on the variant two-step protocol. This variant version can considerably reduce the realization difficulty in experiment. In contrast to the use of multi-particle GHZ states in the case that the sharer number is larger than 3, the use and identification of Bell states are enough in our two protocols disregarding completely the sharer number, hence, our protocols are more feasible in technique