A four-thousand-year history of cryptography ranges from the time of the ancient Egyptian pharaohs to the present, explaining encryption's development and evolution, looking at famous codes, and offering clues for code-breaking.

1. Originality -- Unbroken codes : the Phaistos disk -- Cultural codes : holy codes -- Cultural codes : codes of the Kama Sutra -- 2. Ingenuity -- Cultural codes : Rosslyn's secrets : hidden meaning in architecture and music -- Unbroken codes : the most mysterious book : the Voynich manuscript -- Unbroken codes : the man in the iron mask -- 3. Wit -- Specific codes : the ingenious professor Babbage -- Specific codes : the Playfair cipher -- Unbroken codes : hidden treasure, hidden meaning, the Beale papers -- Unbroken codes : the Dorabella cipher, Elgar's other enigma -- 4. Perseverance -- Specific codes : the enigma machine -- Specific codes : invisible ink and other tools of the spying trade -- Specific codes : purple and Pearl Harbor -- 5. Speed -- Unbroken codes : the Zodiac killer -- Specific codes : cracking Poe's Graham magazine cipher -- Cultural codes : codes in fiction -- 6. Vision -- Specific codes : the cat came back -- Specific codes : quantum cryptography, being in two places at once -- Specific codes : quantum cryptography in a box of chocolates -- Appendix. Code challenge -- Glossary.