  The laws of physics play a crucial role in the security of quantum key
distribution (QKD). This fact has often been misunderstood as if the security
of QKD would be based only on the laws of physics. As the experts know well,
things are more subtle. We review the progresses in practical QKD focusing on
(I) the elements of trust that are common to classical and quantum
implementations of key distribution; and (II) some threats to security that
have been highlighted recently, none of which is unredeemable (i.e., in
principle QKD can be made secure). This leads us to guess that the field,
similar to non-quantum modern cryptography, is going to split in two
directions: those who pursue practical devices may have to moderate their
security claims; those who pursue ultimate security may have to suspend their
claims of usefulness.
