5 ms·

Diffie-Hellman for the Layman

86 points by EntICOnc 5y ago

efitz 5y ago
I skimmed the article and it seems to be a description of a web tool that uses DH or something like it so that two people can come up with a common password without exchanging the password. However, it doesn’t explain the DH algorithm. I suggest re-titling the article for better accuracy.
- anaganisk 5y ago
  To be fair the title doesn't mention "Algorithm".
  - Snawoot 5y ago
    So we should take it refers to actual persons?
  - galoisgirl 5y ago
    That is not fair.
1cvmask 5y ago
Previous discussion here: https://news.ycombinator.com/item?id=26977949 https://news.ycombinator.com/item?id=26977949
mikefallen 5y ago
The math behind DH is pretty simple and really interesting.
- eru 5y ago
  Yes. Though having heard of modulo arithmetic before helps a lot. So eg simple enough for your typical HN crowd. There's also an interesting public key encryption system you can build on top of DH called ElGamal. https://en.wikipedia.org/wiki/ElGamal_encryption https://en.wikipedia.org/wiki/ElGamal_encryption What makes ElGamal so interesting, is that it's probabilistic and that you can easily prove its semantic security (from relatively straightforward assumptions), and more importantly 'indistinguishability under Chosen Plaintext Attack' (https://en.wikipedia.org/wiki/Ciphertext_indistinguishability#IND-CPA https://en.wikipedia.org/wiki/Ciphertext_indistinguishabilit...) Ie even if the attacker can guess your plaintext and knows the public key, they can't be sure that they guessed right.
binbag 5y ago
It's a nice article but it's not for lay people.
- Syzygies 5y ago
  For "lay" people, Whitfield Diffie talked at the Mathematical Sciences Research Institute in 1996 on the politics of communication, with Tim Berners-Lee in the audience. This was one of the best talks I ever attended. The other was Lynn Conway describing how she applied her study of anthropology to initiating a revolution in VLSI design. I did not know or appreciate at the time how being a trans woman also informed her understanding of the revolutionary process.
  - mathewsanders 5y ago
    Do you know if the Lynn Conway talk was recorded and available online?
    - Syzygies 5y ago
      I doubt it. This was mid-80's at Columbia. I'd love to watch it again if you can find it!
deepstack 5y ago
Hmm his "Web tool" is not working. https://borisretiman.com/privacy.html https://borisretiman.com/privacy.html, don't think think the domain is working.
moritonal 5y ago
If anyone is looking for an actual explanation of Diffie-Hellman for the layman, here is my 1-page blog about two kids implementing it on a calculator. https://blog.bonner.is/schoolyard-example-of-the-diffie-hellman-key-exchange/ https://blog.bonner.is/schoolyard-example-of-the-diffie-hell...
- Ennea 5y ago
  That was a very nice explanation, thank you. Side notes regarding your blog: The "subscribe to" text towards the bottom is hard to read against its background. Also, the preview of the "What problem does Polymer solve?" article (also towards the bottom) has raw HTML in it.
fauria 5y ago
If you are looking for an intuitive, visual explanation of the Diffie-Hellman key exchange method I highly recommend watching the video from Computerphile [1] where the color-mixing analogy [2] is put into practice. [1] - https://www.youtube.com/watch?v=NmM9HA2MQGI https://www.youtube.com/watch?v=NmM9HA2MQGI [2] - https://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange#General_overview https://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exc...
- siparikh 5y ago
  Here is another video from "Art of the Problem" that uses the same analogy that really helped me understand this better: https://www.youtube.com/watch?v=YEBfamv-_do https://www.youtube.com/watch?v=YEBfamv-_do
- noman-land 5y ago
  Easily the best layman's explanation out there. Really made it click in my head. I show this to everyone.
- foxyv 5y ago
  I think the color mixing analogy is probably the best. Probably since it's an actual implementation of Diffie-Hellman. The fact that it is so generic is pretty cool. I also like the prime number factorization explanation. It's a little harder to understand, but it's actually used in RSA which is pretty cool.
gjvc 5y ago
Previous discussion here: https://news.ycombinator.com/item?id=26977949 https://news.ycombinator.com/item?id=26977949

86 points by EntICOnc 5y ago

I skimmed the article and it seems to be a description of a web tool that uses DH or something like it so that two people can come up with a common password without exchanging the password. However, it doesn’t explain the DH algorithm. I suggest re-titling the article for better accuracy.

anaganisk 5y ago
To be fair the title doesn't mention "Algorithm".
- Snawoot 5y ago
  So we should take it refers to actual persons?
- galoisgirl 5y ago
  That is not fair.

1cvmask 5y ago

Previous discussion here: https://news.ycombinator.com/item?id=26977949 https://news.ycombinator.com/item?id=26977949

mikefallen 5y ago

The math behind DH is pretty simple and really interesting.

eru 5y ago
Yes. Though having heard of modulo arithmetic before helps a lot. So eg simple enough for your typical HN crowd. There's also an interesting public key encryption system you can build on top of DH called ElGamal. https://en.wikipedia.org/wiki/ElGamal_encryption https://en.wikipedia.org/wiki/ElGamal_encryption What makes ElGamal so interesting, is that it's probabilistic and that you can easily prove its semantic security (from relatively straightforward assumptions), and more importantly 'indistinguishability under Chosen Plaintext Attack' (https://en.wikipedia.org/wiki/Ciphertext_indistinguishability#IND-CPA https://en.wikipedia.org/wiki/Ciphertext_indistinguishabilit...) Ie even if the attacker can guess your plaintext and knows the public key, they can't be sure that they guessed right.

binbag 5y ago

It's a nice article but it's not for lay people.

Syzygies 5y ago
For "lay" people, Whitfield Diffie talked at the Mathematical Sciences Research Institute in 1996 on the politics of communication, with Tim Berners-Lee in the audience. This was one of the best talks I ever attended. The other was Lynn Conway describing how she applied her study of anthropology to initiating a revolution in VLSI design. I did not know or appreciate at the time how being a trans woman also informed her understanding of the revolutionary process.
- mathewsanders 5y ago
  Do you know if the Lynn Conway talk was recorded and available online?
  - Syzygies 5y ago
    I doubt it. This was mid-80's at Columbia. I'd love to watch it again if you can find it!

deepstack 5y ago

Hmm his "Web tool" is not working. https://borisretiman.com/privacy.html https://borisretiman.com/privacy.html, don't think think the domain is working.

moritonal 5y ago

If anyone is looking for an actual explanation of Diffie-Hellman for the layman, here is my 1-page blog about two kids implementing it on a calculator. https://blog.bonner.is/schoolyard-example-of-the-diffie-hellman-key-exchange/ https://blog.bonner.is/schoolyard-example-of-the-diffie-hell...

Ennea 5y ago
That was a very nice explanation, thank you. Side notes regarding your blog: The "subscribe to" text towards the bottom is hard to read against its background. Also, the preview of the "What problem does Polymer solve?" article (also towards the bottom) has raw HTML in it.

fauria 5y ago

If you are looking for an intuitive, visual explanation of the Diffie-Hellman key exchange method I highly recommend watching the video from Computerphile [1] where the color-mixing analogy [2] is put into practice. [1] - https://www.youtube.com/watch?v=NmM9HA2MQGI https://www.youtube.com/watch?v=NmM9HA2MQGI [2] - https://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange#General_overview https://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exc...

siparikh 5y ago
Here is another video from "Art of the Problem" that uses the same analogy that really helped me understand this better: https://www.youtube.com/watch?v=YEBfamv-_do https://www.youtube.com/watch?v=YEBfamv-_do
noman-land 5y ago
Easily the best layman's explanation out there. Really made it click in my head. I show this to everyone.
foxyv 5y ago
I think the color mixing analogy is probably the best. Probably since it's an actual implementation of Diffie-Hellman. The fact that it is so generic is pretty cool. I also like the prime number factorization explanation. It's a little harder to understand, but it's actually used in RSA which is pretty cool.

gjvc 5y ago

Previous discussion here: https://news.ycombinator.com/item?id=26977949 https://news.ycombinator.com/item?id=26977949