  Measurement-device-independent entanglement witness (MDI-EW) will always give
an affirmative certification for witnessing entanglement with untrusted
measurement apparatuses. Using the MDI-EW method, we propose a
measurement-device-independent quantum secret sharing (MDI-QSS) protocol that
Charlie can securely distribute a key between the two agents Alice and Bob. A
tight bound for collective attacks can provide good bounds on the long-distance
MDI-QSS with source flaws. Then we show through numerical simulations that
using single-photon source a secure QSS over 136 km can be achieved.
