If you read this and intend to make security design decisions based on it (as opposed to reading it just for fun), please read more about the subject from other sources as well. A few statements in it are a bit contradictory, like claiming DH is safe from MITM while at the same time in other words acknowledging e.g. that identity cannot be proven with it. I don't mean to bash the author as primers are a good way to get people interested in stuff, but small oversights can sometimes cause big problems.
And before you tackle those other sources, make sure to go on a week-long bender. This will hopefully kill enough brain cells that you might stand a chance of forgetting most of this post's mischaracterizations.
I can condone running through the math behind various primitives, to wet someone's whistle and give them a bit of an appreciation. To someone unfamiliar with the concept of one-way functions, seeing a run through of Diffie-Hellman is pretty neat. "What do you mean I can't figure out the secret, the numbers are right here in front of me..."
But one of the major things that makes crypto so damn hard is that the devil is in the details, and this article misleads much more than it informs. Linear analogies like paint-mixing and XOR (!?) are anti-enlightening to the feat that DH actually accomplishes. Never mind the blatantly incorrect summaries of the properties of each primitive, which were clearly driven more by the limited understanding of the author than any kind of real-world usage.
