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Comment by pawelgut | Hacker News Reader

Diffie–Hellman. I know that cryptography can get much fancier and more clever, but Diffie–Hellman took a concept my intuition told me was impossible and showed that it's possible in a really simple, elegant way. Learning about it was the first time I realized how beautiful the math behind computer science is.

It's also a great insight into just how fundamental the concept of computational complexity is.

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And here is an elegant explanation of the Diffie-Hellman protocol https://www.youtube.com/watch?v=YEBfamv-_do

Absolutely amazing. This is one of those instances when analogy is exact (mixing colors) and doesn't dilute the original motif (One way function).

Another explanation that is not as technically accurate, but really clicked on me to understand how it's possible to establish private communication in the open, is the following:

You put your secret message in a box, put a lock on it that only you have the key to, and send it to the other party. They, unable to open it, put on a second lock of their own, and send it back. You remove your lock, leaving theirs, and once again send it to the other party. Finally, they remove their lock too and can open the box without anyone else having had that possibility.

What can also be inferred from this, is how DH is vulnerable to a man-in-the-middle attack. Someone involved in the delivery could pretend to you to be the other party and to them to be you.

> a concept my intuition told me was impossible and showed that it's possible in a really simple, elegant way

I agree but, to be fair, the key ingredient ("discrete logarithms are hard") is not simple at all.

I am so glad that I took Cryptography as an elective in college even though the course brought down my grades :)

So true. Securely exchanging keys is an abstract concept until you see those paint colors mixing!

I love the idea of how essentially we have never met and we're shouting across a crowded room but no one else can understand our conversation.

Link?

https://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exc...

That's awesome, thanks

There's also this. The paint mixing analogy starts around 3 minutes in.

https://www.youtube.com/watch?v=YEBfamv-_do

Thank you for this. This probably ranks as the algorithm with the greatest coolness / simplicity ratio I've heard of.

+1 for Diffie-Hellman... and the paint analogy.

I was just blown away when my professor taught me this.

Second to this.

Totally blew my mind back then when I was trying to understand how asymmetrical cryptography works.

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