God rewards fools

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God rewards fools
hooman nili
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Solving the key-distribution problem

• The problemBefore two parties can exchange a
  secret (message) over the internet, they must
  share a secret (key) - A classic catch-22
  situation
• A weak link in the chainNo matter how secure a
  cryptosystem is in theory, in practice the
  key-distribution problem can undermine it.
  (Principle of weakest point)
• No apparent solution!For a number of years keys
  were being distributed physically, but it soon
  became a major logistical problem.

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Only three fools could solve it
How the three fools met Ralph Merkle, Martin
Hellman, Whitfield Diffie
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Night time Story God rewards fools
.. To start with, I wanted to be like other
kids, I wanted a Christmas tree and I wanted
Christmas presents. Bu then I realised that I
couldnt be like all the other kids and in
self-defence I adopted an attitude of Who would
want to be like everybody else?.... Our
personalities are very different he is much
more counter-culture that I am but eventually
the personality clash was very symbiotic. It was
just such a breath of fresh air to me. Working in
a vacuum had been really hard Martin Hellman
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Night time Story God rewards fools
Ralph Merkle like us Diffie Hellman was
willing to be a fool. And the way to get to the
top of the heap in terms of developing original
research is to be a fool, because only fools keep
trying. You have idea number 1, you get excited,
and it flops. Then you have idea number 2, you
get excited, and it flops. Then you have idea
number 99, you get excited, and it flops. Only a
fool would be excited by the idea number 100, but
it might take 100 ideas before one really pays
off. Unless you're foolish enough to be
continually excited, you won't have the
motivation, you won't have the energy to carry it
through. God rewards fools. -- Martin Hellman,
on the quest for solving the key-distribution
problem. He is the co-inventor of the
Diffie-Hellman-Merkle key exchange and the
concept of asymmetric ciphers.
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God rewards fools

• How could the fools hope to discover something
  that the NSA (National Security Agency) did not
  know already? And if they did discover anything,
  the NSA would classify it.
• Hellmans colleagues had told him he was crazy to
  do research in cryptography, because he would be
  competing with the NSA and their
  multibillion-dollar budget.

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Modular Maths (all you need to know!)

• To perform an operation on two numbers A and B,
  in mod C
• Do the operation as usual and divide by C.
• The remainder is the answer in mod C
• Example Calculate 9 x 6 in mod 5 i.e. 54 (mod 5)
• 54 5 (10 x 5) 4 Therefore, 54 (mod 5) 4

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A simple illustration

Internet
Choose a number and call it A
Choose a number and call it B
A3
B6
Feed A into the one-way function 7x (mod 11) and
call it ?
Feed B into the one-way function 7x (mod 11) and
call it ?
? 73 (mod 11) 343 (mod 11) 2
? 76 (mod 11) 117649 (mod 11) 4
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A simple illustration

Internet
Send ? to Bob
Send ? to Alice
? 2
? 4
? 2
? 4
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A simple illustration

Internet
Alice calculates
Bob calculates
?B(mod 11)
?A(mod 11)
? 2
? 4
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A simple illustration

Internet
Calculate
Calculate
?A (mod 11) 43 (mod 11) 64 (mod 11) 9
?B (mod 11) 26 (mod 11) 64 (mod 11) 9
?
Alice and Bob have now reached the same number,
9, which will not be transmitted over the
Internet. 9 is their private key!
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Discussion time

• Is key cryptography absolutely secure?
• The future of cryptography

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Useful web resources

• Google
• Search for cryptography
• http//www.rsasecurity.com (good luck!)
• Movie Enigmahttp//en.wikipedia.org/wiki/Enigma_
  (2001_film)
• http//www.gridpp.ac.uk/pics/imagegallery.html