  We critically analyze the results and claims in [Physics Letters A 373 (2009)
901-904].
  We show that the strong security leak appeared in the simulations is only an
artifact and not caused by "multiple reflections". Since no wave modes exist at
cable length of 5% of the shortest wavelength of the signal, no wave is present
to reflect it.
  In the high wave impedance limit, the conditions used in the simulations are
heavily unphysical (requiring cable diameters up to 28000 times greater than
the measured size of the known universe) and the results are modeling artifacts
due to the unphysical values.
  At the low cable impedance limit, the observed artifacts are due to violating
the recommended (and tested) conditions by neglecting the cable capacitance
restrictions and using about 100 times longer cable than recommended without
cable capacitance compensation arrangement.
  We implement and analyze the general circuitry of Liu's circulator and
confirm that they are conceptually secure against passive attacks. We introduce
an asymmetric, more robust version without feedback loop. Then we crack all
these systems by an active attack: a circulator-based man-in-the middle attack.
  Finally, we analyze the proposed method to increase security by dropping only
high-risk bits. We point out the differences between different types of
high-risk bits and show the shortage of this strategy for some simple key
exchange protocols.
