The need for efficient and secure communication has been part of the human experience for the entirety of recorded human history. Especially for those in power and charged with the governance of nations and armies—kings, queens, generals, etc.—communication that can be kept secret and safe is a perpetual necessity. This particular need is what drove the development of modes of communication that would be safe from prying eyes while being simultaneously intelligible to those to whom the message was addressed. As such, the development of codes and ciphers—“techniques for disguising a message so that only the intended recipient can read it” (10)—was a natural development.

The Code Book has two goals. The first goal is to describe and explain the evolutionary development of codes through the course of history up to the present day. As codes are cracked and ciphers are solved, they go through changes that attempt to make them stronger and more impregnable. This process allows codes to evolve over time, becoming increasingly complex as time goes on and the means of breaking them simultaneously increase. The second goal of the book is to prove that the subject matter, though of great importance in times past, is of even greater importance in the present day.