From School Library Journal
Grade 5–8—Many books present readers with codes to crack and puzzles to solve, but this excellent narrative history of cryptography explains who developed the different systems of encryption and why—and who managed to crack the codes. Blackwood offers an accessible and often funny lesson in alternative history that features many names that readers will know (Julius Caesar, Queen Elizabeth I, and Thomas Jefferson, to name a few), as well as those who worked behind the scenes to create what they hoped were unbreakable ciphers. Wherever matters of national security were at stake, cryptography played a major role, and perhaps the most interesting lesson is that many landmark events would have turned out differently had it not been for cryptographers working on both sides to create and break the other side's secret messages. Blackwood provides challenging examples of each type of cipher for readers to try. The book's clever and appealing format, designed to look like a secret notebook of torn pages, photographs, and sketches taped to the pages, complements the subject perfectly. This is an excellent accompaniment to fiction series like Nancy Springer's "Enola Holmes" books (Philomel), which make use of many of the codes and ciphers Blackwood mentions.—Rebecca Donnelly, Loma Colorado Public Library, Rio Rancho, NM
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"Readers with Something To Hide will come away...with not only some new tools, but a great appreciation for the central role codes and ciphers have played in wars and diplomacy through the years." --Kirkus
"[An] excellent narrative history of cryptography." --School Library Journal