  There is a big gap between theory and practice in quantum key distribution
(QKD) because real devices do not satisfy the assumptions required by the
security proofs. Here, we close this gap by introducing a simple and practical
measurement-device-independent (MDI) QKD type of protocol, based on the
transmission of coherent light, for which we prove its security against any
possible device imperfection and/or side-channel at the transmitters' side.
Besides using a much simpler experimental set-up and source characterization
with only one single parameter, we show that the performance of the protocol is
comparable to other MDI-QKD type of protocols which disregard the effect of
several side-channels.
