The number of key exchanges required (p. 90)

[theodore-s-beers]

Correct me if I'm wrong, but the equation provided actually describes the sequence of triangular numbers. (The text in the book says, "The number of key exchanges grows about as fast as the number of people squared.") This isn't a big deal, but I found it interesting. It might be a detail worth adding in the future.

[lvh]

Sure, and the triangle numbers are bounded O(n^2). The goal is to point out that it's faster-than-linear. I'm not sure people have as much of a feel for how big triangular numbers (n(n+1)/2) are compared to just squaring a number.