World War II cryptography

Cryptography was used extensively during World War II, with a plethora of code and cipher systems fielded by the nations involved. In addition, the theoretical and practical aspects of cryptanalysis, or codebreaking, was much advanced.

Probably the most important cryptographic event of the war was the successful decryption by the Allies of the German "Enigma" Cipher. The first complete break into Enigma was accomplished by Poland around 1932; the techniques and insights used were passed to the French and British Allies just before the outbreak of the War in 1939. They were substantially improved by British efforts at the Bletchley Park research station during the War. Decryption of the Enigma Cipher allowed the Allies to read important parts of German radio traffic on important networks and was an invaluable source of military intelligence throughout the War. Intelligence from this source (and other high level sources, including the Fish cyphers) was eventually called Ultra.

A similar break into an important Japanese cypher (PURPLE) by the US Army Signals Intelligence Service started before the US entered the War. Product from this source was called MAGIC. It was the highest security Japanese diplomatic cypher. For Japanese Naval cyphers see JN-25. See also Attack on Pearl Harbor.

Australia

 * Central Bureau
 * FRUMEL: Fleet Radio Unit, Melbourne
 * Secret Intelligence Australia

France

 * PC Bruno
 * Hans Thilo-Schmidt

Germany

 * Enigma (machine)
 * Fish (cryptography) British codename for high level German teletype ciphers.
 * Lorenz cipher one of the Fish ciphers
 * Geheimfernschreiber
 * B-Dienst
 * Reservehandverfahren

Italy

 * used Commercial Enigma

Japan

 * PURPLE
 * JN-25

Poland

 * Cryptanalysis of the Enigma
 * Biuro Szyfrów (Cipher Bureau)
 * Marian Rejewski
 * Jerzy Różycki
 * Henryk Zygalski
 * bomba
 * Lacida Machine

Sweden

 * Arne Beurling

United Kingdom

 * Typex
 * ULTRA
 * Bletchley Park
 * Colossus computer
 * Bombe
 * Alan Turing
 * W. T. Tutte
 * John Tiltman
 * Max Newman
 * Tommy Flowers
 * I. J. Good
 * Leo Marks
 * poem code

United States

 * Magic (cryptography)
 * Signals Intelligence Service US Army, see also Arlington Hall
 * OP-20-G US Navy
 * William Friedman
 * Frank Rowlett
 * Abraham Sinkov
 * Joseph Rochefort
 * Joseph Mauborgne
 * Agnes Meyer Driscoll
 * SIGABA
 * Codetalkers
 * SIGSALY
 * M-209
 * Station HYPO
 * Station CAST
 * Station NEGAT