  Yuan and Shields claim that our data-encryption protocol is entirely
equivalent to a classical stream cipher utilizing no quantum phenomena. Their
claim is, indeed, false. Yuan and Shields also claim that schemes similar to
the one presented in Phys. Rev. Lett. 90, 227901 are not suitable for key
generation. This claim is also refuted. In any event, we welcome the
opportunity to clarify the situation for a wider audience.
