Amazon.com Product Description (ISBN 0486247619, Paperback)

Experiment with cryptography—the science of secret writing. Cipher and decipher codes: transposition and polyalphabetical ciphers, famous codes, typewriter and telephone codes, codes that use playing cards, knots, and swizzle sticks...even invisible writing and sending messages through outer space. Hours of intrigue and challenge. 45 diagrams.

Amazon.com Product Description (ISBN 067165201X, Library Binding)

Explains in simple terms how to encode and decode messages in various ciphers, describes coding machines, and gives formulas for invisible ink.