This book is an introductory text to privacy and traffic analysis, a very important aspect of network security. The target audience for the first edition would be advanced undergraduates reading for a computer security course in Privacy Enhancing Technologies to beginner graduate students preparing to conduct research in this area. Most readers will have to dig very deep into about a thousand or so papers in this area that have been published in the last thirty years. This book provides a gentle introduction to this area while also satisfying the more intellectually oriented student.