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The information leakage problem in the efficient bidirectional quantum secure direct communication protocol with single photons in both polarization and spatial-mode degrees of freedom is pointed out. Next, a way to revise this protocol to a truly secure one is given. We hope people pay more attention to the information leakage problem in order to design truly secure quantum communication protocols. [ABSTRACT FROM AUTHOR]

A deterministic multiparty quantum secret sharing scheme is put forward, in which Bell states in high-dimensional Hilbert space are used. Only by preforming High-dimensional Bell measurements, all agents can recover the secret according to the dealer's announcement when collaborating with each other. It shows that unitary operation for encoding deterministic secret is unnecessary in quantum communication. The security of the transmission of the high-dimensional Bell states can be ensured by randomly using one of the two mutually unbiased bases for eavesdropping checking, and thus by which the proposed quantum secret sharing scheme is secure against usual attacks. In addition, the proposed scheme has three advantages: generality, high resource capacity and high security. [ABSTRACT FROM AUTHOR]

Two quantum secret sharing (QSS) protocols in a multiuser quantum direct communication (QDC) network system were put forward by Hong et al. [Chin. Phys. Lett. 29 (2012) 050303]. However, we find that either agent (Bob or Charlie) alone can obtain half the information about the sender's secret without collaboration with the other, which does not satisfy the security requirement of QSS. Moreover, the secret message sent by Alice in the second protocol can be eavesdropped on or its communication can be disturbed by the builder of quantum channels (Trent). [ABSTRACT FROM AUTHOR]