## Re: Brin: Quantum Cryptography Outperformed By Thermodynamics

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• ... Between ALL communications channels, even the public ones? That s asking rather a lot of Eve. I think there are a lot of people who would use a
Message 1 of 13 , Jun 15, 2012
On 6/15/2012 2:14 PM, KZK wrote:
>>>
>>> Eve cuts the wire between Alice and Bob (AB line) and insert her own
>>> node that connects to Alice (AE line) and Bob (BE Line) individually.
>>> Alice can't tell the difference between the AB line or the AE Line
>>> and sets her resisters. Eve sets her resisters connected on the AE
>>> line to random and deciphers the sequence that Alice used. Eve then
>>> Uses that sequence on the BE Line. Bob can't tell the difference
>>> between the AB line and the BE line, sets his resisters randomly and
>>> decodes the message. (Eve can even send Bob a False message).
>
>> David Hobby Fri, 15 Jun 2012 06:31:29 -0700:
>>
>> I believe that Alice and Bob are doing the resistor thing for each
>> bit simultaneously, and sharing their measurements over a separate
>> open channel.
>
> And so Eve man-in-the-middles the second connection too. So all of
> Alice and Bob's communications are with eve, so that (Eve and Alice)
> And (Eve and Bob) are doing the resistor thing for each bit
> simultaneously (but not Alice and Bob, they have no connection with
> each other), and (Eve and Alice) And (Eve and Bob) are sharing their
> measurements over the separate lines (but not Alice and Bob, they have
> no connection with each other). Bob still can't tell the difference
> between Eve and Alice and Alice can't tell the difference between Eve
> and Bob.
> ...
> Doesn't matter, so long as Eve is between all communications channels.

Between ALL communications channels, even the public ones? That's asking
rather a lot of Eve. I think there are a lot of people who would use a
cryptographic
system that required an additional open channel, confident that they
could somehow
route around Eve most of the time. (Alice and Bob could be just posting
their
versions of the public information on their respective websites, and
checking that
they agreed.)

But yes, it's a minor flaw that was not mentioned in the press release.

---David

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• ... I think you can be forgiven, particularly if there s any chance that your Bay Area friends can buy you a drink while you re here. If you have any time in
Message 2 of 13 , Jun 15, 2012
On Jun 14, 2012, at 11:21 PM, David Brin wrote:

Sorry for the salesmanship, but I'm working hard!  And it has been 8 years since a "big brin book" so I hope you don't mind!

I think you can be forgiven, particularly if there's any chance that your Bay Area friends can buy you a drink while you're here. If you have any time in the evening, I'd like to see you, and one or two others maybe, too?

Dave

• ... And so Eve man-in-the-middles the second connection too. So all of Alice and Bob s communications are with eve, so that (Eve and Alice) And (Eve and Bob)
Message 3 of 13 , Jun 15, 2012
>> On 6/15/2012 2:37 AM, KZK wrote:
>>
>> > But Eve, who is listening in to the publicly available noise, does
>> > not know which resistor was connected at each end and cannot work it
>> > out either because the laws of thermodynamics prevent the extraction
>> > of this information from this kind of signal.
>>
>>
>> So why isn't this susceptible to a simple man in the middle attack?:
>>
>>
>> Eve cuts the wire between Alice and Bob (AB line) and insert her own
>> node that connects to Alice (AE line) and Bob (BE Line) individually.
>> Alice can't tell the difference between the AB line or the AE Line
>> and sets her resisters. Eve sets her resisters connected on the AE
>> line to random and deciphers the sequence that Alice used. Eve then
>> Uses that sequence on the BE Line. Bob can't tell the difference
>> between the AB line and the BE line, sets his resisters randomly and
>> decodes the message. (Eve can even send Bob a False message).
>>
>>
>> Seems like this method requires a 100% secure land line, which is
>> impractical.
>
> David Hobby Fri, 15 Jun 2012 06:31:29 -0700:
>
> I believe that Alice and Bob are doing the resistor thing for each
> bit simultaneously, and sharing their measurements over a separate
> open channel.

And so Eve man-in-the-middles the second connection too. So all of
Alice and Bob's communications are with eve, so that (Eve and Alice) And
(Eve and Bob) are doing the resistor thing for each bit simultaneously
(but not Alice and Bob, they have no connection with each other), and
(Eve and Alice) And (Eve and Bob) are sharing their measurements over
the separate lines (but not Alice and Bob, they have no connection with
each other). Bob still can't tell the difference between Eve and Alice
and Alice can't tell the difference between Eve and Bob.

> (The paper says the voltage/current data on the noisy
> channel is "public".) Furthermore, they're tossing all the trials
> where those data show they both picked the "high" resistors or both
> picked the "low". So all Eve can usefully look at are data for
> essentially identical trials, each one with the noise characteristic
> of one high and one low resistor on the channel. Eve is free to relay
> noise between the two lines in your example, but that won't help
> her.

Doesn't matter, so long as Eve is between all communications channels.

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• Sure wish I could participate, but I m headed to the Big Boulder conference, in Boulder, Colorado, that weekend... disappointed! Nick ...
Message 4 of 13 , Jun 15, 2012
Sure wish I could participate, but I'm headed to the Big Boulder conference, in Boulder, Colorado, that weekend... disappointed!

Nick

On Fri, Jun 15, 2012 at 11:04 AM, Dave Land wrote:
On Jun 14, 2012, at 11:21 PM, David Brin wrote:

Sorry for the salesmanship, but I'm working hard!  And it has been 8 years since a "big brin book" so I hope you don't mind!

I think you can be forgiven, particularly if there's any chance that your Bay Area friends can buy you a drink while you're here. If you have any time in the evening, I'd like to see you, and one or two others maybe, too?

Dave

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• ... So Eve Man-in-the-middles Bob s connection to his webserver. Bob thinks he s writing information to correlate with Alice. What actually happens is Eve
Message 5 of 13 , Jun 15, 2012
> David Hobby Fri, 15 Jun 2012 10:35:51 -0700:
>
> Between ALL communications channels, even the public ones? That's
> asking rather a lot of Eve. I think there are a lot of people who
> would use a cryptographic system that required an additional open
> channel, confident that they could somehow route around Eve most of
> the time. (Alice and Bob could be just posting their versions of the
> public information on their respective websites, and checking that
> they agreed.)

So Eve Man-in-the-middles Bob's connection to his webserver. Bob thinks
he's writing information to correlate with Alice. What actually happens
is Eve replaces the data Bob uses with the data from the Eve-Alice
connection. When Bob is connected to the website he see's the
information he thinks he's posted (Because Eve knows to change it back
for him, and only him, (also Alice's website data must be changed for
Bob and only Bob)). Etc.

Complicated? Yes, But plausible (this is sort of how the Sony Rootkit
worked).

> But yes, it's a minor flaw that was not mentioned in the press
> release.

Seems like it might be impractical. CITOKATE.

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• ... FYI: Pretty sure you need the colon in Brin: for messages to be sent to DB. _______________________________________________
Message 6 of 13 , Jun 15, 2012
> Dave Land
> Fri, 15 Jun 2012 11:04:21 -0700
>
> I think you can be forgiven, particularly if there's any chance that your Bay
> Area friends can buy you a drink while you're here. If you have any time in the
> evening, I'd like to see you, and one or two others maybe, too?

FYI: Pretty sure you need the colon in "Brin:" for messages to be sent
to DB.

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• At every stop, there should be a What s next? question. In a message dated 6/14/2012 11:21:34 P.M. US Mountain Standard Time, dbrin@sbcglobal.net writes: Ask
Message 7 of 13 , Jun 15, 2012
At every stop, there should be a "What's next?" question.

In a message dated 6/14/2012 11:21:34 P.M. US Mountain Standard Time, dbrin@... writes: