Daniel Kahn’s Seizing The Enigma is the story of the ENIGMA machine, a electro-mechanical cipher system used by the German’s during WWII, and ULTRA the British code breaking effort of the ENIGMA (and other Axis encodings and encipherments). Daniel Kahn is a leading historian of cryptographic history and it shows in his ability to stitch together a story which does not focus on one person (such as Turing or Welchman), but instead covers the German’s, the navy, and Bletchley Park (the headquarters of the British code breakers). The descriptions of the encoding, and code breaking methods, are easy to follow. However, the real point the book drives home is how pure mathematical analysis is important, but it in a problem like cryptography it can prove that something is “very difficult” to break, without taking into account implementation, and human, details which change the mathematical facts. The breaking of the ENIGMA is a beautiful interplay between mathematical rigor, engineering, espionage and social reasoning. I think this will change the way I think about problems going forward. This applies not just in the domain of cryptography, but also safety of systems which have high consequence. A mathematically provably safe system can be useful, but it is the social aspects and variables that were not controlled for that can still cause issues and incidents! This is not to say that we should not provide rigor, but instead that mathematical and engineering rigor are a basis, and that data collection and skepticism are necessary to improve and maintain a system.