  Nishioka et al claim in [1], elaborating on their earlier paper [2], that the
direct encryption scheme called Y-00 [3,4] is equivalent to a classical
non-random additive stream cipher, and thus offers no more security than the
latter. In this paper, we show that this claim is false and that Y-00 may be
considered equivalent to a \emph{random} cipher. We explain why a random cipher
provides additional security compared to its nonrandom counterpart. Some
criticisms in [1] on the use of Y-00 for key generation are also briefly
responded to.

Quantum Physics