Cryptography: Cracking Codes

98 Pages·2013·12.63 MB·english

by  Rob Curley

Published in 2013 by Britannica Educational Publishing
(a trademark of Encyclopædia Britannica, Inc.)
in association with Rosen Educational Services, LLC
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First Edition
Britannica Educational Publishing
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Introduction by Richard Barrington
Library of Congress Cataloging-in-Publication Data
Intelligence and counterintelligence: cryptography: cracking codes/edited by Rob Curley.—
First edition.
pages cm
"In association with Britannica Educational Publishing, Rosen Educational Services."
Includes bibliographical references and index.
ISBN 978-1-62275-034-4 (library binding)
1. Cryptography—History. 2. Data encryption (Computer science) I. Curley, Robert. II.
Title: Cryptography: cracking codes.
Z103.I68 2013
005.8'2—dc23
2012035291
Manufactured in the United States of America
On the cover, pp. i, iii: Binary code. Comstock/Thinkstock
Cover (top front and back) © www.iStockphoto.com/Yucel Yilmaz; ba ck cover © www.
iStockphoto.com/Alexander Putyata; pp. 1, 15, 30, 41, 50, 63, 75, 77, 78 © www.iStockphoto.
com/Olga Yakovenko; pp.12, 27, 28, 38, 43, 44, 59, 60, 67 © www.iStockphoto.com/Molnár
Ákos
Contents
Introduction viii
Chapter 1: Cryptography,
Cryptanalysis, and Cryptology 1
The Fundamentals of Codes,
Ciphers, and Authentication 2
Cryptology in Private and
Commercial Life 8
9
Identity Theft 12
Chapter 2: Cipher Systems 15
Transposition Ciphers 15
Substitution Ciphers 17
Playfair Ciphers 18
Vigenère Ciphers 20
Vernam-Vigenère Ciphers 24
William and Elizebeth Friedman 27
Product Ciphers 28
27
Chapter 3: Key Systems and
Block and Stream Ciphers 30
Single-Key Cryptography 30
Two-Key Cryptography 31
Public-Key Cryptography 33
Secret-Sharing 35
RSA Encryption 36
Prime Numbers 38
Block and Stream Ciphers 39 32
Chapter4: Cryptanalysis 41
Basic Aspects 42
The Zimmermann Telegram 43
Types of Cryptanalysis 46
Chapter 5: Early Manual and
Mechanical Cryptography 50
42 The First Systems 51
World Wars I and II 54
Alan Turing’s Bombe 59
Chapter 6: Modern Electronic
Cryptography 63
The Impact of Electronics 64
Fibonacci’s Numbers 67
DES and AES 68
Conclusion 74
57 Glossary 75
Bibliography 77
Index 78

IntroductIon
Binary code. Spaxiax/Shutterstock.com
viii
T
he world of secret messages and code
breakers might seem like something out
of a high-tech espionage thriller, but the fasci-
nation we have with cryptology and its methods
in novels has been inspired by some very real
practices. At times, these practices have helped
change history, and while cryptology continues
to adapt by using cutting-edge technology, it
is a science—and to some extent an art—with
roots that go back to ancient times.
This book will let you in on the secrets of
cryptography and code breaking, including
their colourful history, the extremely intricate
structures that go into cryptographic systems,
and the high-level puzzle-solving required to
break a code. In the process, you will see both
sides of a cat-and-mouse game: those who are
trying to devise impenetrable codes, and those
who are trying to crack those codes.
Given the long history of the practice, it is
appropriate that the word cryptography comes
from ancient Greek. It literally means “hidden
writing,” and the practice is one of trying to
conceal messages in plain sight. Cryptanalysis
represents the other side of game: the practice
of trying to decipher or forge messages written
in someone else’s code. Cryptology is a broad
description of the overall field, encompassing
both cryptography and cryptanalysis.
Talk of secret messages and code break-
ers evokes images of spies and international
diplomacy, and cryptology continues to play
ix