What is the difference between a code and a cipher? How did Caesar send secret messages? How do you beat frequency analysis? What is a side channel attack? How does RSA end-to-end encryption actually work? In this fascinating little book, packed with numerous 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 to someone special, this book will show you how.