Today is the birthday of William Friedman, one of the fathers of modern cryptology and an unsung American hero from World War II.
Before Friedman, cryptology could be described at best as a hodgepodge of tricks and unproven methods for securing information. Some tricks worked better than others. But there was no math in cryptology to quantify the strength (and exploit the weaknesses) of ciphers, really, until Friedman came along and brought the power of modern statistical techniques to bear on such problems as breaking rotor-machine ciphers. He almost single-handedly broke the Japanese PURPLE cipher, and in what’s surely one of the greatest problem-solving feats of all time, his team was able to complete reconstruct a PURPLE cipher machine using only plaintext and ciphertext samples — no technical diagrams were used.
He later suffered a major nervous breakdown, blamed mostly on his intense work on the PURPLE problem. I don’t think most human beings would have lasted even as long has he did and would have gone much further over the edge.
Here’s a page on Friedman at the National Security Agency web site. And here’s the Wikipedia article on Friedman. He’s a fascinating figure in both math history and American history, and more people should know about him.