  The Ekert 91 quantum key distribution (QKD) protocol appears to be secure
whatever devices legitimate users adopt for the protocol, as long as the
devices give a result that violates Bell's inequality. However, this is not the
case if they ignore non-detection events because Eve can make use of the
detection-loophole, as Larrson showed. We show that even when legitimate users
take into account non-detection events Eve can successfully eavesdrop if the
QKD system has been appropriately designed by the manufacturer. A loophole
utilized here is that of `free-choice' (or `real randomness'). Local QKD
devices with pseudo-random sequence generator installed in them can apparently
violate Bell's inequality.
