[14225] in cryptography@c2.net mail archive
Re: quantum hype
daemon@ATHENA.MIT.EDU (R. Hirschfeld)
Sat Sep 20 11:35:16 2003
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Date: Sat, 20 Sep 2003 13:37:29 +0200
From: "R. Hirschfeld" <ray@unipay.nl>
To: iang@systemics.com
Cc: cryptography@metzdowd.com
In-reply-to: <3F6B2762.41756307@systemics.com> (message from Ian Grigg on Fri,
19 Sep 2003 11:57:22 -0400)
Reply-To: ray@unipay.nl
> Date: Fri, 19 Sep 2003 11:57:22 -0400
> From: Ian Grigg <iang@systemics.com>
> If I understand this correctly, this is both
> an eavesdropping scenario and an MITM scenario.
>
> In the above, Eve is acting as Mallory, as she
> is by definition intercepting the bits and re-
> sending them on?
As Dave Howe pointed out, Eve is acting as a repeater and tries not to
alter the bits. This seems a sensible model of eavesdropping for QKD.
The threat is that Alice and Bob might incorporate bits that were seen
by Eve into their key. If Bob never receives a bit, it won't be used.
> That is, the "Quantum Property" is that Eve can
> be detected because she destroys photos in the
> act of listening, and Mallory, who can resend
> the photons, has only a 50% chance of reading
> each bit correctly in advance, so he can be
> detected after the fact as well, as 25% of his
> bits are wrong.
The terminology "destroy" is used a bit loosely. I think the
important thing for QKD is that if a photon is measured with the wrong
basis, the information it is carrying about the key is lost.
Ray
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