John Denker writes:
A much better strategy for Eve is to _not_ make so many
measurements. Rather, she should preserve the photon in all its analog,
quantum-mechanical glory and recirculate it back to Bob, bypassing the
other participants in the ring.
Then Bob, in blissful ignorance,
This message analyzes the Shining Cryptographers network in terms of
how much information Eve the eavesdropper can hope to get by measuring
the photon state before and after it is rotated. See earlier messages
for more detail about how the SC Net works.
This analysis will focus on one
At 10:10 AM 1/20/01 -0800, [EMAIL PROTECTED] wrote:
This analysis will focus on one particular kind of attack. Eve will make
measurements of the photon polarization angle as it travels through the
network and attempt to deduce information about the signals being sent
by the participants.
This
On Thu, 18 Jan 2001 [EMAIL PROTECTED] 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.
At 02:04 PM 1/18/01 -0800, [EMAIL PROTECTED] wrote:
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;
Right, it is. Here's a Gedankenexperiment: temporarily trap the signal
Ray Dillinger wrote, quoting me:
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
In the `traditional' DC Net, how is absence of a message detected?
If this is a seperately distinguishable outcome of a round, each round may
return three outcomes: `0', `1' and `none'. To represent these quantum
mechanically, you need at least a 3-state quantum system (to make the outcomes
Jaap-Henk Hoepman, [EMAIL PROTECTED], writes:
In the `traditional' DC Net, how is absence of a message detected?
A practical implementation of a DC Net would require multiple protocol
layers. The lowest layer is the "raw" DC net itself, which has the
property that each person sends a bit
At 11:20 PM 1/17/01 -0800, [EMAIL PROTECTED] wrote in part:
The probability that Eve's measurement will leave the result unchanged is
3/4, and therefore the probability that she will perturb the result is 1/4.
OK so far. Then, for the case of two measurements,
Eve's chances of perturbing the
John Denker, [EMAIL PROTECTED], writes:
Eve need not limit herself to snooping "the signal". What she really wants
to know is the "state of mind" of the participants, i.e. the settings of
their rotators. If she knows that, she knows everything. She can, as a
final step, synthesize a
At 08:35 PM 1/16/01 -0800, [EMAIL PROTECTED] wrote:
To recap, a group of cryptographers wants to communicate anonymously,
without the sender of a message being traced.
To recap in more detail, as I understand it:
1) The desired result is a plain broadcast message, open to the world
hey aren't supposed to. There has been various
work done on tracing disruptors. Similar extensions to the simple
Shining Cryptographers net would be needed once actual evidence of
Eve's manipulation is detected. (In addition the SC Net is equally as
vulnerable to disruptors as the DC Net, of course.
At 10:35 PM 1/15/01 -0800, [EMAIL PROTECTED] wrote:
Here is a rough idea for a quantum-cryptography variant on the DC Net,
the Dining Cryptographers Net invented by David Chaum.
The photon starts off with vertical polarization. Each cryptographer
manages a station through which the photon
John Denker, [EMAIL PROTECTED], writes:
At 10:35 PM 1/15/01 -0800, [EMAIL PROTECTED] wrote:
Here is a rough idea for a quantum-cryptography variant on the DC Net,
the Dining Cryptographers Net invented by David Chaum.
Hmmm. This seems like a mistake in the physics. If the attacker, Eve,
Let me follow up on the Shining Cryptographers idea with a more careful
analysis of the last proposal I made in my earlier posting.
To recap, a group of cryptographers wants to communicate anonymously,
without the sender of a message being traced. They do so by circulating
a photon around a
The Shining Cryptographers Net
Here is a rough idea for a quantum-cryptography variant on the DC Net,
the Dining Cryptographers Net invented by David Chaum. It does not
provide as much anonymity as the DC Net, but perhaps will inspire others
to look for a more powerful design.
In a simple
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