First quantum crypto bank transfer

Bill Stewart bill.stewart at
Tue Aug 24 00:58:26 EDT 2004

At 02:02 AM 8/23/2004, Florian Weimer wrote:
>* Bill Stewart:
> > I agree that it doesn't look useful, but "lawful intercept" is harder,
> > if you're defining that as "undetected eavesdropping with
> > possible cooperation of the telco in the middle",
> > because quantum crypto needs end-to-end fiber so there's
> > nothing the telco can help with except installing dark fiber,
> > and the quantum crypto lets you detect eavesdroppers.
>But this doesn't scale.
>You'd need dark fiber to all communication partners.

Yes.  That's part of one definition of "doesn't look useful".

>So if quantum key distribution was mandated for
>applications involving more than just a handful communication
>partners, you'd need relays (or rather unlikely advances in optical
>circuit switching).

It would be possible to use it as link encryption,
giving up the benefits of end-to-end in return for better scaling,
but you could still make all the relaying happen in the
user organization's facilities, rather than in a telco building
that's outside the user organization's control.
(Just because something isn't very useful doesn't mean you can't
at least try to do the job semi-correctly...)

>By the way, the complete bashing of the recent QKD experiment is
>probably not totally deserved.  Apparently, the experimenters used a
>QKD variant that relies on quantum teleportation of photons.
>This QKD variant is currently *not* available commercially,
>and the experiment itself could well be an important refinement of
>Zeilinger's earlier work in this area.

That's at least interesting, though I don't see why you'd take
the experiment out of the lab without a really well-defined
benefit to the end user (unless you've got a research grant.)
I'm surprised to hear that _any_ quantum key distribution variant
is available commercially, given the costs of dedicating fiber
and the effectiveness of current mathematical crypto
or the alternative approach of couriers with briefcases and handcuffs.

Bill Stewart  bill.stewart at 

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