3.5 out of 5 stars
A copy of this was provided free of charge from the publisher in return for an honest review.
One of my favourite books when I was (much) younger was the Spy’s Guidebook that was published by Usborne. It was hardly subtle for those wanting to be a spy with its bright red cover, but it was in here that I first learnt about the discipline of codes and the stick scrambler. I want to be a spy when I grew up; inevitably I didn’t…
The need to pass on information to another person without it becoming public knowledge has been important over history, in fact, they can trace the first codes back to the Egyptians where the scribes would change the hieroglyphs to convey a different meaning to anyone reading them. The Romans were also known to use them and it is said that Caesar always used a cipher anything confidential. The Greeks used cryptography too, but they used the technique of steganography for getting messages to the desired recipient. The principle behind this is to disguise the fact that there even is a message, and one of the way that they did it was to tattoo the message onto the head of a slave, let their hair grow back and send them on their way. This, as you can imagine, had several disadvantages… The primary one being the speed of the message reaching its destination and secondly that they could only be used to do this once or possibly twice.
Being able to make and deliver coded messages was one thing, but being able to break them was another step up. The first explanation of cryptoanalysis was in the 9th century by the Arabic scholar Abu Yusuf Yaqub ibn Ishaq al-Sabbah Al-Kindi. Where he mentions frequency analysis for the first time. The simple substitution and transposition ciphers which changed one letter for another didn’t take much effort to crack, but others, such as the were harder to do so, but these new tools meant that it became much easier to do.
It is this mathematical arms race between the latest code and cipher techniques and methods of cracking them that was one of the key factors in World War 2. The Nazis were using a machine called Enigma that could have up to 158 million million different ways of setting up the machine. The Germans thought that it was unbreakable. It wasn’t thanks to a trio of Polish mathematicians who constructed a device they called a cyclometer using parts from an enigma machine to generate all 100,00 permutations of the rotors. They succeeded. Then the Nazi’s changed the way they set up the rotors and so the Poles devised a machine called a bomba that could automatically search for the rotor settings. It worked for a time and the Nazi’s changed their methods again. The Poles passed their machines and knowledge onto the French and the English and they ended up at Bletchley Park. It was here that the mathematical and mechanical geniuses of Turning and Flowers set about building a mechanical computer that could rapidly check the letters over the 18,000 possible rotor combinations. They broke their first code on 20th January 1940 and ultimately changed the course of the war.
The American had their own cipher system, SIGABA, which was much better than Enigma, but was little use in the field as it could take hours to code and decode messages. A man called Philip Johnson had the bright idea of using native Navajo to send messages with coded words in their own language. Virtually no one outside of their community could speak this language and it was ideal for passing highly detailed messages onto units in combat quickly.
A lot of the techniques that were developed in the war were used after for encryption and breaking during the cold war, but it was the advent of the internet that modern encryption came of age. The last time that you used some form of encryption was moments ago when you looked at a website or bought something from it. The tools that are used at the moment are factorials of large prime numbers that keep your data and financial transactions safe are very sophisticated and can only be broken using huge super-computers, of which a number of intelligence agencies across the world handily own… The is a brief chapter on the wonders of quantum computers and the uncrackable codes that this technology promises.
This is a fascinating book full of clearly written explanations of the various codes and cipher that have been used over history. There is a little bit on modern encryption, bitcoins and so on, but not much on contemporary codes as ciphers, but that is to be expected. I thought that the page layouts were really clear with extensive use of colour photos and diagrams to go with the text. If there was one flaw, I did feel that the narrative was sometimes broken up by the explanatory sections. I would often read to the end of the chapter and then go back and read those parts after. It gives a good overview, but for more detail then The Code Book by Simon Singh is probably your next point of call.