Cryptography: The Science of Secret Writing

The wartime primer that taught a generation of American amateurs to read and write ciphers, and stayed in print long enough to teach several more.

Norton published it in 1943, at a point when cryptography had a large civilian audience and almost no published literature to serve it. Smith works upward from concealment devices and simple substitution through Playfair, Vigenere and transposition systems to the mechanics of breaking them by frequency analysis, then sets problems and prints the answers at the back, which is what the jacket subtitle promises. 164 pages, grey cloth under a black and red jacket carrying a Polybius square.

Dover reprinted the book and kept it available for decades, which is how most readers met it; copies in the original Norton jacket are less common. On a shelf of this kind it sits beside Helen Fouche Gaines's Elementary Cryptanalysis of 1939 as one of the two self-teaching texts an interested amateur could actually get hold of before David Kahn's The Codebreakers opened the subject up in 1967.