[8476] in cryptography@c2.net mail archive
Re: The Shining Cryptographers Net
daemon@ATHENA.MIT.EDU (Ray Dillinger)
Fri Jan 19 11:09:34 2001
Date: Thu, 18 Jan 2001 16:03:39 -0800 (PST)
From: Ray Dillinger <bear@sonic.net>
To: hal@finney.org
Cc: cryptography@c2.net, jsd@research.att.com
In-Reply-To: <200101182204.OAA23251@finney.org>
Message-ID: <Pine.LNX.4.21.0101181554330.215-100000@bolt.sonic.net>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
On Thu, 18 Jan 2001 hal@finney.org wrote:
>> Or does somebody have a good defense against this hyper-active attack?
>
>The only thing I can suggest would be if the rotation stations could
>somehow count or limit the number of photons going through so that they
>would know when there were extra. I think this is possible in theory;
>whether it can be done in practice is questionable.
Hm? As far as I know there's no way to detect (count) a photon
that doesn't affect its quantum state in some way that can be
later detected. In this case, that's not an option, because you're
trying to use the quantum state to transmit information. If you
fiddle with it by trying to count photons, the information will
change.
Is there a detector that affects some *other* part of the Quantum
state, and won't mess with the polarization?
>Another idea would be for the stations to actually absorb the photon
>in some manner that preserved its polarization, and then to re-emit it.
>These could be primed to pass only a single photon.
Now you are talking serious voodoo. I don't think that this
can be done this year. Maybe not this decade.
Bear
