Maybe you made the mistake of watching The Imitation Game, a film about Alan Turing and the British code breaking unit that deciphered the German’s Enigma during World War II. If this were your first or one of a few encounters with the art/science of cryptography, you might think that codes are broken by socially reclusive savants in lightbulb moments of frenetic realization and then all one has to do is plug the code into a machine and let it spit out the positions of the U-boats. Here’s the scene from the Imitation Game:
As if it had only, just in this moment, occurred to Britain’s top cryptographic minds that finding repeated words in cipher text could help lead to its decryption. In fact, techniques such as this have been in the toolbox of codecrackers for hundreds, if not thousands of years. Clearly, this film had other agendas aside from giving us a gripping narrative lesson in cryptography. Fortunately, there are books that do take up the call, namely Simon Singh’s The Code Book, which reads like an ideal combination of handbook, history and thriller stretching from Ancient Greece to the frontiers of quantum physics.
With a patient pace, Singh takes us through this millennia-old battle between cryptographers (encryptors) and cryptanalysts (decryptors), taking time to teach us the lexicon of the field as well as wrapping the techniques in helpful metaphors. Here’s a taste of what I’m talking about:
“Cracking a difficult cipher is akin to climbing a sheer cliff face. The cryptanalyst is seeking any nook or cranny which could provide the slightest purchase. In a monoalphabetic cipher the cryptanalyst will latch on to the frequency of the letters, because the commonest letters, such as e, t and a, will stand out no matter how they have been disguised. In the polyalphabetic Vigenère cipher the frequencies are much more balanced, because the keyword is used to switch between cipher alphabets. Hence, at first sight, the rock face seems perfectly smooth.”
Singh describes in detail famous ciphers and methods used to decrypt them, including Mary Queen of Scots letters of conspiracy, The Zimmerman Telegraph, and the Enigma (featured in The Imitation Game). There are a number of themes that Singh distills from these events, namely the importance of concealing the ability to crack a code, the tradeoff between security and convenience, and the penetrability of supposedly impenetrable ciphers.
This is great first book for people that have been piqued by instances of cryptography in media or curious about the algorithms that secure the web. By the end, you’ll understand terms like Caesar Shift, frequency analysis, cribs, and the fundamental concepts of public and private keys that digital currencies such as bitcoin depend upon.
This is an introduction to cryptography so If you already have a strong understanding of these concepts, this is not a book for you. Although it might be a good read for a father or friend that wants to appreciate your work.