CAN YOU CRACK THE CODE?

Hands-on history for budding spies, hackers, or anyone with a secret message to send.

Though she starts off with a face-plant—a vague claim, with a disappointingly stereotypical illustration, that “the ancient Chinese” had couriers swallow secret messages written on silk—Schwartz goes on to offer a broad and lucid survey of cryptographic strategies. These range from steganography and substitution ciphers to second factor authentication and other recent trends in cybersecurity. She also provides plenty of variously coded examples for readers to decipher as practice, capped by a final challenge to go back and find the clues to a secret message that have been distributed throughout. Her detailed description of how the German Enigma machine worked (and was hacked by the Bletchley Park group in World War II) is indeed “fascinating,” as are the close analyses of still-unsolved messages such as the modern Kryptos inscription outside CIA headquarters. Somewhat less fascinating are the closing chapters, in which she does explain how prime numbers figure in securing internet communications but neglects to mention the possibilities of quantum cryptography and leaves a debatable impression that cyber defenses have been generally successful in staying ahead of “black hat” hackers. Williams adds a diverse group of spot-art figures to go with the array of tables, diagrams, and occasional photos.

A serviceable if too-often superficial update for solid but now-dated histories such as Gary Blackwood’s Mysterious Messages (2009).