

Ask HN: What do you find tricky about Public Key Cryptography? - ColinWright

The other day I was explaining the Diffie-Hellman_Merkle-Williamson key exchange and public key crypto system to someone, and while they understood every individual step, they didn't really seem to "Get It".  They really started to struggle as I got into the connections between this an P versus NP, and they finally lost it when I was talking about NP complete and various algorithms.<p>Of course, it may have just been me, so I was wondering about the audience here on HN - is there anything in this area that you just don't "get", and would you be interested in having me try my explanations on you?
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patio11
That seems like explaining gene heritability with a quick detour through
organic chemistry to explain on a molecular level how DNA gets unzipped. Did
the person need to know those details? Were they obviously capable of
understanding them? If there are not two "yes" answers here, one might
question the likely success of attempting to cram half a college class into
their heads in a session.

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ColinWright
They were asking the questions, and I was sketching a map of things only as
they arose as a necessary part of answering them. I agree, it seems like a
detour, but actually it's a bit like Dirk Gently - everything really is
connected.

I'm thinking of writing up this farrago of topics and trying to make sense of
the connections between them for those who are interested, but I was
interested in hearing people's reactions to the topic. In essence, though,
there hasn't been any. Which is disappointing, but there we go.

So I think it's two "yes" answers. They were asking the questions, so I felt
that answering them was necessary. There were other questions that I dodged
because they were too much of a diversion. And yes, I do feel that the person
in question was sufficiently capable, they just didn't really "get it" at the
end. Perhaps they just need time to absorb some of the specifics, and then
next time they'll be in a better place and get further.

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vmilner
I think one problem is that both DH and RSA depend on the fact that finding
inverses is hard in certain big groups, which isn't an intuitive
idea.(Admittedly, in RSA, the idea that factoring is hard is intuitive, but
then you have the problem that the fact that the big composite number gives
you a group, isn't).

I always find it a shame that Fermat's Little Theorem, and multiplicative
groups aren't taught earlier in a typical maths education, as the beauty
returned from a small effort is significant.

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debacle
Diffie-Hellan is a pretty simple algo. You can do a frame-by-frame analysis of
it in about fifteen minutes and it should be fairly easy to understand.

The trickiest thing about public key cryptography is that I always lose my
keys!

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runT1ME
Monads and why they're useful (in application)

(I understand, but I just find it fascinating that no two monad explanations
seem to be similar on the surface...)

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ColinWright
I'm curious as to what you think the connection is between monads and Public
Key Crypto.

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runT1ME
Oh. I misunderstood. I thought you were asking for examples of other 'easy to
understand' mathematical concepts that programmers get stuck on that you could
try explaining.

I admit, public key crypto isn't always easy to explain, but I believe it has
more to do with it being non intuitive opposed to overly abstract or math
heavy (though obviously the implementations are).

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drallison
The tricky thing about cryptography is key-management with secure key-exchange
a close second.

