Secret writing for the transmission of messages has been practiced for nearly 4,000 years. According to David Kahn, the great historian of cryptology, the first example of an intentionally altered message can be traced to a tomb in ancient Egypt dated about 1900 b.c. In the 40 centuries since that event, secret messages have been used by politicians and diplomats, military officers and infantrymen, smugglers and thieves, retail merchants and bankers, officials and scholars of the highest rank, and the simplest citizens of nations around the world.
In some respects, the history of cryptology is a record of some of the most brilliant and arcane intellectual accomplishments known to the human race. A series of contests has developed between, on the one hand, men and women committed to the development of secret systems that no one but the intended recipients can solve and, on the other hand, equally committed workers searching out the flaws in such systems, endeavoring to ensure that no such system is produced.
In recent years, the struggles between those who produce systems of secret writing—the cryptographers—and those who try to break those systems—the cryptanalysts—have made use of mathematical systems of dizzying complexity. Indeed, in the late twentieth century mathematics has taken cryptology far beyond the comprehension of all but the most sophisticated students. In addition, the most advanced computer technology available has been enlisted in the production of ever more complex and elegant methods of writing and breaking systems of secret writing.
Yet throughout the history of cryptology, secret writing has been totally immersed in social, political, economic, military, and personal issues of immense intrigue and interest. Some of the greatest decisions of history have been made as the result of secret messages successfully sent or intercepted and deciphered. Presidential elections have been lost, great battles won, and the innocent wrongly convicted of crimes and the guilty released.
This book attempts to provide an introduction to the grand panorama that is cryptology. First, some of the basic fundamental concepts of cryptography and cryptanalysis are introduced. In some respects, these concepts are simplicity itself. Secret writing involves essentially one of two approaches: the rearranging of words and/or letters or the substitution of one word or letter for another. These techniques—transposition and substitution—and their many variations are described in the text.