  It is claimed in Phys. Lett. A by T. Nishioka et. al. 327 (2004) 28-32, that
the security of Y-00 is equivalent to that of a classical stream cipher. In
this paper it is shown that the claim is false in either the use of Y-00 for
direct encryption or key generation, in all the parameter ranges it is supposed
to operate including those of the experiments reported thus far. The security
of Y-00 type protocols is clarified.
