Spy Codes and CiphersBook - 2012
Can flashing lights send out a secret message? Did a famous spy use sketches of butterflies to hide messages? Can a digital photo hide a secret code? For centuries, spies have used many different ways to pass secret information. Codes and ciphers keep information safe from the enemy. Author Susan K. Mitchell uncovers the secrets to the amazing world of spy codes and ciphers.
Publisher: Berkeley Heights, NJ : Enslow Publishers, c2012
Characteristics: 48 p. :,col. ill. ;,24 cm. --