A mathematical tour of some of the greatest unsolved ciphers of all time In 1953, a man was found dead from cyanide poisoning near the Philadelphia airport with a picture of a Nazi aircraft in his wallet and an enciphered message taped to his abdomen. In 1912, a book dealer named Wilfrid Voynich came into possession of an illuminated cipher manuscript once belonging to Emperor Rudolf II, who was obsessed with alchemy and the occult. Wartime codebreakers tried--and failed--to unlock the book's secrets, and it remains an enigma to this day. In this lively and entertaining book, Craig Bauer examines these and other vexing ciphers yet to be cracked. Some may reveal the identity of a spy or serial killer, provide the location of buried treasure, or expose a secret society--while others may be elaborate hoaxes. He lays out the evidence surrounding each cipher, describes the efforts to decipher it, and invites readers to try their hand at puzzles that have stymied so many others.