Improving the security of multiparty quantum secret splitting and quantum state sharing

A protocol for multiparty quantum secret splitting (MQSS) with an ordered N Einstein-Podolsky-Rosen (EPR) pairs and Bell state measurements is recently proposed by Deng et al. [F.G. Deng et al., Phys. Lett. A 354 (2006) 190]. We analyzed the security of the protocol and found that this protocol is secure for any other eavesdropper except for the agent Bob who adopts intercept-and-resend attack. Bob can obtain all the information of Alice's alone without being found. We also propose an improved version of the MQSS protocol.