[ale] OT: Diffie-Hellman key exchange for dummies?

[List]

Jay,

I sort of hope somebody disagrees with me, but, the short answer to your 
question is no, this really is black magic unless you want to learn some 
of the basics of number theory and set theory which underly what is 
going on here.  In general terms, why it works is related to some of the 
magic of prime numbers, and some very clever computational insights that 
Diffie, Hellman, and (independently) Merkle figured out.  The secret 
sauce is that it is really easy to multiply two prime numbers together 
and get an answer, but it is very difficult to take the answer and 
figure out what the two prime numbers were.  Beyond that the math gets 
pretty deep pretty fast.

One of the inventors (Martin Hellman) wrote a very readable piece about 
the technology for the IEEE 30 years ago called "An Overview of Public 
Key Cryptography" which is available here: 
http://www.comsoc.org/livepubs/ci1/public/anniv/pdfs/hellman.pdf

Tom

Jay Loden wrote:
> This is somewhat off topic for a Linux enthusiast group, but this a group of smart folks with lots of knowledge, so I figured it might be a good place to ask anyway:
>
> I've heard the term "Diffie-Hellman Key Exchange" used before, and in basic terms I know that it's a secure way of agreeing on a secret key. However, when I tried to read a couple of articles to understand how it works under the hood, I found myself out of my depth. I have programming experience, but I'm not formally trained, and I never went beyond Algebra 2. Even though I was able to implement a simplistic version of the exchange by following the Linux Journal article below I don't really understand why it works on a mathematical level.
>
> Anyone who likes a challenge feel like trying to explain in laymen's terms to a mathematically challenged individual? :-)
>
> References:
> http://en.wikipedia.org/wiki/Diffie-Hellman
> http://www.rsa.com/rsalabs/node.asp?id=2248
> http://www.linuxjournal.com/article/6131
> http://en.wikipedia.org/wiki/Discrete_logarithm
>
> -Jay
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