The Code Book by Simon Singh

Hurray! I think my brain is finally beginning to recover!

I've had this book on my shelf for years, but while I was going to work programming everyday it just looked like more work. Maternity leave was the right time to read it. Either my brain is starting to work properly again or Singh writes with enough clarity to penetrate the mum-fog. Probably a bit of both.

The code book is a history of cryptography from the Ceasar cypher (good enough for 1000 years then broken by Arab scholars) through to quantum cryptography. The Caesar cipher was followed by polyalphabetic ciphers (in the case of the one time pad the key is as long as msg therefore unbreakable but logistical problems distributing keys mean this method must be used sparingly). We then come to the mechanisation of encoding and the Enigma machine. The section on the breaking of the Enigma cipher was especially interesting as I had never realised the contribution made by the Polish secret service as well as the more familiar story of Bletchly Park. In many cases it was human weaknesses that made the messages decodeable ( for example, the choice of 3 letter day codes was left to the individual operators who would sometimes get lazy and use their own initials, or letters which were next to one another on the Enigma machine keyboard). Another trick was to realise that a certain message at 6am was always a weather report, so you could expect the word "wetter" near the beginning. We then move on to RSA and PGP. For the future we have the possibility of quantum cryptography. There are also interesting asides on the translation of the Rosetta Stone and linear b.

Great stuff. I feel enthused to have a go at the cyphers in the back. Then I'm going to decode the Voynich manuscript, solve the travelling salesman problem and sort out 3 body physics before the end of maternity leave...