This book explores the ways and means of conveying secret information from antiquity to the present, including physical devices, codes, the mechanics of secret telling, and spy's tradecraft. "How to" directions and historical context are also provided. Although many examples from the military and spy agencies will be given (the authors will enlist the aid of historians at the National Cryptological Museum), the book will also cover the layman's use of technology, e.g., decoder rings and gadgets from movies and TV shows. A fun subject with broad appeal and a strong title for our popular history subject category.