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Can You Crack the Code?

Can You Crack the Code? A Fascinating History of Ciphers and Cryptography

Ella Schwartz, Illustrated by Lily Williams
128 pp.
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Readers who think it would be fun to send secret messages—i.e., practically all of them—will enjoy this book, which is both a brief history of encryption and a beginner’s how-to manual. Ella Schwartz, a cybersecurity expert, uses a breezy style that itself is never cryptic, and Lily Williams’s illustrations make the concepts readily accessible.

The book begins with a simple substitution cipher, used by Julius Caesar, in which every letter of the alphabet is signified by another letter a specific number of spots away. It then works through more-complicated substitution ciphers, symbolic ciphers, and ciphers in which a message is spelled out in the first letters of specific words in a specific book. Schwartz poses puzzles so the reader can try the schemes. She describes Enigma, the complex cipher used by the Germans, and cracked by the British, during World War II, and the basic idea behind internet encryption.

Along the way, Schwartz provides fascinating examples of codes that have long defied decryption. For example, in 1990 the U.S. Central Intelligence Agency installed at its headquarters in Langley, Virginia, a sculpture in which artist Jim Sanborn encrypted a message. Even the agency’s cryptographers have yet to completely decipher it.

The book might have gone a tad deeper and explained how digital messages consist of binary numbers and how one can be encrypted, for example, using a string of random zeros and ones that only the sender and the receiver share. Such a discussion might have set up the chapter on internet encryption more concretely.

But that’s a quibble. The book should inspire students who enjoy puzzles to invent their own ciphers. As Caesar might have put it, vjku dqqm ku c nqv qh hwp!

About the author

The reviewer is a news reporter at Science.