Secret flag signals were used extensively on the battlefield in the American Civil War.
American codebreaker William Friedman invented several cryptologic machines, two of which were so secret patents were never filed.
Narrator: Caesar altered his alphabet, the Nazi's had Enigma, computers and digital encryption, the attempts to make and break these secret methods of scrambled communication have changed have changed the course of history. Now: Codes, on Modern Marvels.
Dr. David Hatch
Director, Center for Cyptologic History
Dr. David Kahn
Author, The Codebreakers
Author, Battle of Wits
Bletchley Park Codebreaker
President, Navajo Codetalkers Association
Inventor, Pretty Good Privacy
Prof. Leonard Adleman
Co-Inventor, RSA Crypto Cipher
Dr. Dorothy E. Denning
Professor, Georgetown University