Scientific American on Quantum Encryption

Tyler Durden camera_lumina at
Thu Jan 20 08:43:53 PST 2005

What do you mean? By a physical fiber switch? That's certainly possible, 
though you'd need a very good condition switch to be able to do it. I'd bet 
if that switch switched a lot, the QCrypto channel would eventually be 

If you're talking about a WDM element or passive splitter or other purely 
optical component, then you'd need some kind of error correction (in the 
digital domain) in order to overcome the fact that many of the photons will 
not choose to go in the direction you want.

In the long run I think we'll see some small proliferation, but given the 
level of integration and how well current coding schemes work, I'd guess 
this will remain a niche unless there's a major breakthrough in factoring.


>From: "Trei, Peter" <ptrei at>
>To: "Eugen Leitl" <eugen at>, <transhumantech at>
>CC: <cypherpunks at>
>Subject: RE: Scientific American on Quantum Encryption
>Date: Thu, 20 Jan 2005 10:47:38 -0500
>I've actually seen these devices in operation. The thing
>that impressed me most was that the path need not be a
>single fiber from end to end - you can maintain quantum
>state across a switchable fiber junction. This means
>you are no longer limited to a single pair of boxes talking to
>each other.
>True, the SciAm article doesn't address a lot of issues,
>but the fact remains that this technology is interesting
>and important.
>Peter Trei
> > -----Original Message-----
> > From: owner-cypherpunks at
> > [mailto:owner-cypherpunks at]On Behalf Of Eugen Leitl
> > Sent: Thursday, January 20, 2005 6:17 AM
> > To: transhumantech at
> > Cc: cypherpunks at
> > Subject: Scientific American on Quantum Encryption
> >
> >
> >
> > Scientific American has little clue, as usual (see their
> > nanotechnology
> > retraction).
> >
> > Link:
> > Posted by: samzenpus, on 2005-01-20 06:35:00
> >
> >    from the just-try-and-break-it dept.
> >    [1]prostoalex writes "Scientific American claims that
> > [2]advances in
> >    commercially available quantum encryption might obsolete
> > the existing
> >    factorization-based solutions: "The National Security
> > Agency or one of
> >    the Federal Reserve banks can now buy a
> > quantum-cryptographic system
> >    from two small companies - and more products are on the
> > way. This new
> >    method of encryption represents the first major commercial
> >    implementation for what has become known as quantum information
> >    science, which blends quantum mechanics and information theory. The
> >    ultimate technology to emerge from the field may be a
> > quantum computer
> >    so powerful that the only way to protect against its prodigious
> >    code-breaking capability may be to deploy quantum-cryptographic
> >    techniques.""

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