Girish Mahajan (Editor)

World War II cryptography

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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 codebreaking 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 ciphers) was eventually called Ultra.

A similar break into an important Japanese cipher (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 cipher.


  • 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 teleprinter ciphers.
  • Lorenz cipher one of the Fish ciphers
  • Short Weather Cipher
  • Geheimfernschreiber
  • B-Dienst
  • Reservehandverfahren
  • Gisbert Hasenjaeger
  • Italy

  • Hagelin machine
  • Enigma machine
  • Japan

  • Japanese naval codes
  • JN-25
  • Poland

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

    As is common with World War II discussions of cryptology, there is a curious absence of information on Soviet efforts and accomplishments. Given the Red Army offenses on the Eastern Front, they must have obtained Enigma machines. What they did with them seems to be an unanswered question.


  • Arne Beurling
  • United Kingdom

  • Bletchley Park
  • Cryptanalysis of the Enigma
  • Far East Combined Bureau (FECB)
  • Wireless Experimental Centre (WEC)
  • Bombe
  • Colossus computer
  • Typex
  • Ultra
  • Alan Turing
  • W. T. Tutte
  • John Tiltman
  • Max Newman
  • Tommy Flowers
  • I. J. Good
  • John Herivel
  • 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
  • Codetalkers
  • M-209
  • Station HYPO
  • Station CAST
  • Station NEGAT
  • References

    World War II cryptography Wikipedia

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