Cryptanalysis and Improvement of a Quantum Network System of QSS-QDC Using χ -Type Entangled States

In the paper [Chin. Phys. Lett. 29 (2012) 050303] of Hong et al., two quantum secret sharing protocols were proposed. We study the security of the second protocol and find that it is insecure. Acting as the communication center, Trent may eavesdrop Alice's secret messages without introducing any error. Finally, a feasible improvement of the second protocol is given.