A must-have book for secret agents in the making. Ever wondered how to make and crack codes and ciphers? Herbie Brennan's essential guide contains everything a serious cryptographer and code-buster needs, including: - Codebreaking methods, examples and tests - How to develop complex ciphers - Tools for encrypting messages, from invisible ink to computer pixels - A history of how codes and ciphers have developed, taking in the ancient Greeks, the Kama Sutra, the Enigma machine and computer ciphers And much, much more! Contains black-and-white illustrations throughout.