How do you make invisible ink? Or disguise your speech? What's the best way of beating frequency analysis? What is a side channel attack? How does RSA end-to-end encryption actually work? In this illuminating little book, packed with helpful illustrations and worked examples, polymath Steven Goodwin reveals the secrets of the codermakers, and the toolkits of the codebreakers. If you ever wanted to send a secret message, then this book will show you how.