Re: The Elevator Problem

s1113645@tesla.cc.uottawa.ca writes:
>
>
>On Sun, 10 Dec 1995, Daniel Miskell wrote:
>
>> There is an easy way to develop a secret key in front any number of eves, 
>>be  they experts or not, without the eves knowing what the key is.  Even if 
>>they  tap your phone/comm line, ect.  There was an article in Discovery 
>>Magazine a  couple of years ago, talking about how to use photons and their 
>>randomness as  the perfect, uncrackable code.  Use of the photons aside, 
>>there was a key  generation method discussed, simple, yet secure enough to 
>>work out on a tapped  phone.  Let me root around.
>
>You must mean quantum crypto, by G. Brassard and C. Crepeau of U de Montreal.
>Requires a direct fiber optic line from pt. A to B, in order to be 
>secure, if I am not mistaken. Which makes it impractical for most people, 
>as there are usually switches (or whatever they're called) and more than one 
>line in between. Lets you use OTPs with your next-door neighbor though.

I think i was misunderstood.  I was not referring to the actual use of light 
in the communications process.  I was talking about the key generation method 
suggested in that article.  Of course the use of light is impractical for most 
- the need for direct fiberoptics aside, you have to be able to test a photon 
for its polarized orientation.  In any case, i dig on.

Regards,
Munster.

---
_________________________________
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and aged to perfection, one must
not yield to produce mold.  One
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melt over the unprocessed ideas
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_________________________________

On Sun, 10 Dec 1995, Daniel Miskell wrote:

> I think i was misunderstood.  I was not referring to the actual use of light 
> in the communications process.  I was talking about the key generation method 
> suggested in that article.  Of course the use of light is impractical for most 
> - the need for direct fiberoptics aside, you have to be able to test a photon 
> for its polarized orientation.  In any case, i dig on.

I didn't read the Discover article, but I did see it in Applied Crypto, 
1st edition. The polarization thing was used for eavesdropper detection, 
rather than key generation (I think, and I may be quite wrong).

The paper was intended to show that you could have unconditional security
even if P=NP (I even think that was one of the paper titles), so the authors
used a one time pad (and used whatever key generation method is usually used
for OTPs, ie coin flips, real RNGs and whatnot). So nothing special or new 
with regards to key generation. (Of course they may have newer papers...Any 
hints folks?)

Incidentally, Brassard wrote a nice and very short intro to modern crypto
that's in the Springer-Verlag Lecture Notes in Computer Science series.
I think Applied Cryptology was the title. It had good coverage of his quantum
crypto scheme. It ought to be in any university library.

On Sun, 10 Dec 1995 I mistakenly wrote:

> Incidentally, Brassard wrote a nice and very short intro to modern crypto
> that's in the Springer-Verlag Lecture Notes in Computer Science series.
> I think Applied Cryptology was the title. It had good coverage of his quantum
> crypto scheme. It ought to be in any university library.

Sorry, it's Modern Cryptology: A tutorial, 1988.
You'll find good info in <http://www.iro.umontreal.ca/labs/theorique>
(the titles are in french, but don't worry, the text in the "cryptographie
quantique" section is in english and has plenty of links to papers. Also
weird stuff like quantum teleportation. You'll also see Brassard and 
Crepeau's home pages.)

If you run into the listing for the Discover article, please pass it on,
I keep putting that one off.