Dogs, Shells, Retro Crypto, etc.

I’ve written several unrelated posts since the previous newsletter.

The latest post is motivated by yesterday’s announcement of the discovery of new Hadamard matrices. The post looks at ways to construct new Hadamard matrices from old ones, so the new discoveries can be bootstrapped into even more possibilities, which could be useful in applications.

Before that I wrote about how the bash shell, and artifacts of Unix culture in general, are internally consistent even if they seem cryptic.

The distribution of dog names in NYC fits a log-normal distribution remarkably well.

Suppose you could travel back in time. Given what we know now about cryptography, could you give someone an encryption method that could be carried out by hand but not broken by hand?

Donald Knuth’s take on what we can learn from historical mistakes.

Instead of solving a differential equation to find out what its solutions look like, you might want to go the other way around and find a differential equation that functions of interest satisfy. Explanation here.

That’s it. Enjoy.