It's known as the science of secrecy. Cryptography: the encoding and decoding of private information. And it is history's most fascinating story of intrigue and cunning. The battle between codemakers and codebreakers has been going on for centuries: from Julius Caesar and his Caesar cipher to the codebreaking achievements of the 10th-century Arabs; from the code used by Mary Queen of Scots in an attempt to dethrone Elizabeth I to Sir Francis Walsingham's decipherment of that code, which led to Mary's execution for treason; from the Germans' use of the Enigma machine for automatic encryption in the Second World War to Alan Turing's efforts to infiltrate Enigma, which contributed to the Allied victory. 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? Simon Singh follows the evolution of secret writing with a clarity that lets the reader enjoy the captivating story while easily absorbing the details of cryptography. Woven throughout are clear and concise illustrations of the processes of enciphering and deciphering.