School Library Journal (Tue Dec 01 00:00:00 CST 2009)

Gr 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 whyand 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

Kirkus Reviews

Writing with the same animation that infuses his other accounts of historical enigmas and events ( Perplexing People , 2006, etc.), Blackwood plunges into the history of codes and ciphers, cryptograms, nomenclators and steganography. In chapters with headers like "Babington, Beer, and Baconian Biliteralism," he traces many of the ways—from simple to brain-bendingly complicated—that messages have been concealed, from the earliest surviving example (a formula for pottery glaze coded in cuneiform and estimated to date from 1500 BCE) to today's "public key" cryptography. Along with plenty of photos or images of important code makers and breakers, he supplies (relatively) easy-to-use sidebar examples, charts and instructions for several systems. Readers with Something To Hide will come away from this engaging companion to the even more hands-on likes of Paul Janeczko's Top Secret: A Handbook of Codes, Ciphers and Secret Writing (2004) 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. (Nonfiction. 11-16)

ALA Booklist (Thu Oct 01 00:00:00 CDT 2009)

This well-written history of cryptography begins with a pottery-glaze formula encrypted in cuneiform on a clay tablet (1500 BCE) and traces the uses of secret messages in statecraft, espionage, warfare, crime, literature, and business up to the present. Along the way, Blackwood, whose historical novels include Second Sight (2005) and The Shakespeare Stealer (2007), discusses the historical development of coding and encryption and tells many good stories of messages ciphered and deciphered, particularly in English and American history. For readers motivated to understand the codes and ciphers mentioned in the text, he stops to explain their principles and how to use them. The many sidebars and illustrations, including photos, reproductions of artworks and artifacts, and the pictures demonstrating the codes themselves, contribute to the book's approachable look. Source notes for quotes, a bibliography, a glossary, and lists of recommended fiction, nonfiction, and Internet sites are appended. A solid introduction to a topic of perennial interest.

Horn Book (Thu Apr 01 00:00:00 CDT 2010)

Blackwood presents an engaging look at code development and usage. The text begins with the ancient Greeks and other ancient cultures then moves through early Western history to the World Wars to today and beyond. The well-organized information, including specific examples (some effectively illustrated with black-and-white drawings), will inspire readers to follow the models and maybe even create their own codes. Reading list, websites. Bib., glos., ind.

Voice of Youth Advocates

In a standout example of middle grade nonfiction, this cleverly designed, engaging book will answer every question about codes and ciphersùand then some. Well-organized information, presented in chronological sequence (with fifteen chapters ranging from ôClay, Wax, and Greece [1500 BCE-100 BCE]ö to ôColossus, Lucifer, and Kryptos [1945 CE-]ö) is enhanced with a glossary, a brief ôSelected Sourcesö list, a page devoted to related information (including fiction, nonfiction, and online resources), and a comprehensive index. Most pages include a photograph, image, sidebar, or example code. Quotes are referenced in a separate list in the back of the bookùnot cited in textùwhich might discourage some readers from exploring primary sources, but the fact that the information is included adds to the integrity of the book. Although the text is presented with engaging, accessible language and lends itself to being read in its entirety, each chapter can be read independently, which will allow the reader with a specific interest to quickly locate and use the information needed. A nicely crafted balance of information about individual people, world events, and technology ensures that the text never feels heavy. Enough background information is offered to orient young readers to the topics discussed, but the authorÆs focus on codes and ciphers is what makes this book so strong. With a topic, style, and format sure to engage middle grade readers, this book will be a great fit for almost any school or public library collection.ùEllworth Rockefeller.