One-insider attack of quantum secret sharing protocol with collective eavesdropping-check

Recently, a kind of quantum secret sharing protocol with collective eavesdropping check was proposed by Lin et al. In this paper, we present a one-insider attack against Lin's three-party protocol. With the method of intercept-resending and entanglement-swapping, we show that the insider participant who performs the last local operation on the qubit sent by the secret sender could illegally extract the secret messages without being detected. This greatly improves the two-insider-collaborating attacks proposed by Gao and Liu, respectively. Furthermore, such an attacking method also applies in the n-party version of such a secret sharing protocol. Our attack method once more shows the power of intercept-resend attack and poses the importance of information authentication in quantum and classic communications.