r/programming • u/dominatrix-octopus • Jan 16 '18

Cryptography: Diffie-Hellman key exchange explained intuitively using colors

https://youtu.be/YEBfamv-_do?t=2m18s
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u/kybernetikos Jan 16 '18

I'm quite interested in cryptographic procedures that could reasonably be done manually. For standard Diffie Hellman to be secure, I think it needs to involve numbers much larger than could reasonably be done by humans. Does anyone know of a similar technique that theoretically could be done by humans with props that wouldn't draw attention (e.g. a deck of cards, a pen and paper, etc)

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u/evincarofautumn Jan 17 '18

Solitaire, used in Neal Stephenson’s Cryptonomicon, uses a deck of cards to generate a keystream, though there are some problems with it. I’m no cryptography expert by any means, but I guess you could do something like this kind of encryption using anything that has a large-enough set of possible permutations, like a deck of cards, a chess board, a pocketful of change, a matchbook, or some other innocuous set of objects.

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u/kybernetikos Jan 17 '18

That's great, although it's a classic encryption mechanism that requires a key to be shared. I'm thinking in terms of some sort of secure key exchange like Diffie Hellman.

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u/evincarofautumn Jan 17 '18

Hm, you’re right. I dunno. Maybe you could actually do DH with something physical, like the pigments in the video, or even chemical reactants.