Type A Cipher Machine
In the
The Red cipher should not be confused with the Red naval code, which was used by the Imperial Japanese Navy between the wars. The latter was a codebook system, not a cipher.
Operation
The Red machine encrypted and decrypted texts written in
Encryption itself was provided through a single half-rotor; input contacts were through
The rotor turned at least one step after each letter. The amount of rotation was controlled by the break wheel, which was connected to the rotor, and which had up to forty-seven pins in it. Up to eleven of these pins (in a predetermined set of positions) were removable; in practice, from four to six pins were removed. Rotation of the wheel stopped when the next pin was reached; therefore, if the next pin were removed, the rotor would advance two places instead of one.[2] The irregular pattern of rotation produced an Alberti cipher.[4]
History
The vulnerability of Japanese code systems was made public in 1931 when Herbert Yardley published The American Black Chamber, a popular account of his code breaking activities for the US government in which he discussed the breaking of Japanese codes and their use during the Washington Naval Conference. These revelations prompted Japanese to look into machine ciphers.[5]
The system was introduced in 1930–1931 (the 91 in the designation refers to the Japanese imperial year 2591),[6] using a reverse-engineered version of a machine supplied by the firm of Boris Hagelin.[7] Hagelin's most sophisticated systems were rotor machines similar to those used in World War II, but as he did not trust the Japanese to honor his patents, he sent a more primitive device designed by Arvid Damm instead.[7] It was this machine which the Japanese used as the basis for their design; the separate encryption of the vowels, however, was strictly a Japanese contribution.[7]
The code was broken successfully by three independently working groups. The British solution came first, with
The PURPLE machine began to replace the RED system in 1938, but initial installations were at major posts; less important embassies and consulates continued to use the old system. A far more serious deficiency was that the PURPLE machine maintained the "sixes/twenties" division, even though the RED machines had since been modified to allow any six letters to be used for the vowel encryption. After eighteen months of work, the PURPLE device was cracked, and produced important intelligence up to the end of the war.
Intelligence results of RED intercepts were not as dramatic, but important intelligence was obtained. For instance, American cryptanalysts were able to provide details of the Tripartite Pact between the Axis powers.[5][10] Reports of the sea trials of the battleship Nagato were also decoded, leading to important changes to the USS North Carolina (BB-55), then being designed, in order to match the performance of the Japanese ship.[3]
Further reading
- Chapter 7 of Computer Security and Cryptography (Konheim, Alan G., Wiley-Interscience, 2007, pp. 191–211) has an extensive analysis of the RED cipher.
References
- OCLC 59019141
- ^ a b c Savard, John J. G. "The RED Machine". Retrieved 2009-04-21.
- ^ a b Budiansky, Stephen (2000). Battle of Wits: The Complete Story of Codebreaking in World War II. New York: The Free Press. pp. 84–88.
- ^ a b c d Bauer, Friedrich Ludwig (2007). Decrypted Secrets: Methods and Maxims of Cryptology. Springer. pp. 154–158.
- ^ a b c d "Pearl Harbor Review - Red and Purple". National Security Agency. Retrieved 2009-04-03.
- ^ a b Smith, Michael (2000). The Emperor's Codes:The Breaking of Japan's Secret Ciphers. New York: Arcade Publishing. pp. 45–47.
- ^ a b c "Pearl Harbor Review - Early Japanese Systems". National Security Agency. Retrieved 2009-04-03.
- ^ Haufler, Hervie (2003). Codebreakers' Victory: How the Allied Cryptographers Won World War II. New American Library. p. 114.
- ^ Budiansky, p. 164.
- ISBN 978-0-06-092178-1. Retrieved 2009-04-21.