Summary

It's Known As the science of secrecy. Cryptography: the encoding and decoding of private information. It spans generations and is history's most fascinating story of intrigue and cunning. Julius Caesar created his own code, the Caesar Cipher, to protect his messages. Mary Queen of Scots employed a code in her attempt to dethrone Elizabeth I. The Enigma machine was manufactured for the automatic encryption of messages during the Second World War. And the battle rages on. How private are your e-mail communications? How secure is sending your credit card information over the Internet? And how much secrecy will the government tolerate? Accessible, compelling and timely, Simon Singh's international bestseller, adapted for young people, is sure to make readers see the past -- and the future -- in a whole new way. Book jacket.

Author Biography

Simon Singh is the author of Fermat’s Enigma and The Code Book. He lives in London. From the Hardcover edition.

Introduction	p. 1
The Cipher of Mary Queen of Scots: The birth of cryptography, the substitution cipher and the invention of codebreaking by frequency analysis	p. 5
The Anonymous Codebreaker: The Vigenere cipher, why cryptographers seldom get credit for their breakthroughs and a tale of buried treasure	p. 51
The Mechanization of Secrecy: The Zimmermann telegram, the Enigma machine and how cryptography changed the courses of World Wars I and II	p. 95
The Language Barrier: The impenetrability of unknown languages, the Navajo code talkers of World War II and the decipherment of Egyptian hieroglyphs	p. 152
Alice and Bob Go Public: Modern cryptography, the solution to the so-called key-distribution problem and the secret history of nonsecret encryption	p. 180
Pretty Good Privacy: The politics of privacy, the future of cryptography and the quest for an uncrackable code	p. 221
The Codebreaker's Challenge	p. 243
Appendices	p. 245
Acknowledgments	p. 253
Further Reading	p. 255
Picture Credits	p. 260
Index	p. 261
Table of Contents provided by Ingram. All Rights Reserved.

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Excerpts

1

The Cipher of Mary Queen of Scots

The birth of cryptography, the substitution cipher and the invention of codebreaking by frequency analysis

On the morning of Saturday, October 15, 1586, Queen Mary entered the crowded courtroom at Fotheringhay Castle. Years of imprisonment and the onset of rheumatism had taken their toll, yet she remained dignified, composed and indisputably regal. Assisted by her physician, she made her way past the judges, officials and spectators, and approached the throne that stood halfway along the long, narrow chamber. Mary had assumed that the throne was a gesture of respect toward her, but she was mistaken. The throne symbolized the absent Queen Elizabeth, Mary's enemy and prosecutor. Mary was gently guided away from the throne and toward the opposite side of the room, to the defendant's seat, a crimson velvet chair.

Mary Queen of Scots was on trial for treason. She had been accused of plotting to assassinate Queen Elizabeth in order to take the English crown for herself. Sir Francis Walsingham, Elizabeth's principal secretary, had already arrested the other conspirators, extracted confessions and executed them. Now he planned to prove that Mary was at the heart of the plot, and was therefore equally to blame and equally deserving of death.

Walsingham knew that before he could have Mary executed, he would have to convince Queen Elizabeth of her guilt. Although Elizabeth despised Mary, she had several reasons for being reluctant to see her put to death. First, Mary was a Scottish queen, and many questioned whether an English court had the authority to execute a foreign head of state. Second, executing Mary might establish an awkward precedent--if the state is allowed to kill one queen, then perhaps rebels might have fewer reservations about killing another, namely, Elizabeth. Third, Elizabeth and Mary were cousins, and their blood tie made Elizabeth all the more squeamish about ordering her execution. In short, Elizabeth would sanction Mary's execution only if Walsingham could prove beyond any hint of doubt that she had been part of the assassination plot.

The conspirators were a group of young English Catholic noblemen intent on removing Elizabeth, a Protestant, and replacing her with Mary, a fellow Catholic. It was apparent to the court that Mary was a figurehead for the conspirators, but it was not clear that she had given her blessing to the conspiracy. In fact, Mary had authorized the plot. The challenge for Walsingham was to demonstrate a clear link between Mary and the plotters.

On the morning of her trial, Mary sat alone in the dock, dressed in sorrowful black velvet. In cases of treason, the accused was forbidden counsel and was not permitted to call witnesses. Mary was not even allowed secretaries to help her prepare her case. However, her plight was not hopeless, because she had been careful to ensure that all her correspondence with the conspirators had been written in cipher. The cipher turned her words into a meaningless series of symbols, and Mary believed that even if Walsingham had captured the letters, he could have no idea of the meaning of the words within them. If their contents were a mystery, then the letters could not be used as evidence against her. However, this all depended on the assumption that her cipher had not been broken.

Unfortunately for Mary, Walsingham was not merely principal secretary, but also England's spymaster. He had intercepted Mary's letters to the plotters, and he knew exactly who might be capable of deciphering them. Thomas Phelippes was the nation's foremost expert on breaking codes, and for years he had been deciphering the messages of those who plotted against Queen Elizabeth, thereby providing the evidence needed to condemn them. If he could decipher the incriminating letters between Mary and the conspirators, then her death would be inevitable. On the other hand, if Mary's cipher was strong enough to conceal her secrets, then there was a chance that she might survive. Not for the first time, a life hung on the strength of a cipher.

From the Hardcover edition.

Excerpted from The Code Book for Young People by Simon Singh
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