Red (cipher machine)
Encyclopedia
In the history of cryptography
, 91-shiki injiki (九一式印字機) ("System 91 Printing Machine") or Angōki Taipu-A (暗号機 タイプA) ("Type A Cipher Machine"), codenamed Red by the United States, was a diplomatic cryptographic machine used by the Japanese Foreign Office before and during World War II
. A relatively simple device, it was quickly broken by western cryptographers. The Red cipher was succeeded by the "Purple" machine ("97-shiki ōbun inji-ki") which used some of the same principles. Parallel usage of the two systems assisted in the breaking of the Purple system.
The Red cypher 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.
by encyphering the vowel
s separately from the consonant
s, so that the text remained a series of syllables. (The letter "Y" was treated as a vowel.) The "sixes and twenties" effect (as American analysts referred to it) was a major weakness which the Japanese continued in the Purple system.
Encryption itself was provided through a single half-rotor; input contacts were through slip ring
s, each of which connected to a single output contact on the rotor. Since both the vowels and consonants were passed through the same rotor, it had sixty contacts (the least common multiple
of six and twenty); wiring ensured that the two groups were kept separate. The slip rings were connected to the input keyboard through a plugboard
; again this was organized to keep the vowels and consonants separate.
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. The irregular pattern of rotation produced an Alberti cipher
.
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 cyphers.
The system was introduced in 1930-1931 (the 91 in the designation refers to the Japanese Imperial Year 2591), using a reverse-engineered
version of a machine supplied by the firm of Boris Hagelin
. Hagelin's most sophisticated systems were rotor machine
s similar to those used in World War II
, but as he did not trust the Japanese to honor his patent
s, he sent a more primitive device designed by Arvid Damm
instead. 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.
The code was broken successfully by three independently working groups. The British solution came first, with Hugh Foss
and Oliver Strachey
working out the code in 1934, and Harold Kenworthy's shop producing a replica, the "J machine", a year later. American attempts to break the system waited until 1935. In the Army SIS
group, the system was broken by Frank Rowlett
and Solomon Kullback
; for the navy, Agnes Driscoll is generally credited. (She actually solved the Orange (or M-1) cipher used by naval attaches, but as it turned out the two systems were essentially the same.) The Americans also constructed a replica machine to expedite solutions; interestingly, this machine had two half-rotors to solve the vowels and consonants separately. The SIS group originally referred to it simply as the "Japanese code machine", but decided that so descriptive a term was a security risk; as it was the first Japanese machine cipher solved, they decided to start at the beginning of the spectrum, and named it "RED".
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. This was one of many deficiencies in Japanese use of encryption that helped make the PURPLE system vulnerable to cracking, for now there was some identical traffic on both systems, which allowed cribbing. 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. Reports of the sea trial
s 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.
History of cryptography
The history of cryptography begins thousands of years ago. Until recent decades, it has been the story of what might be called classic cryptography — that is, of methods of encryption that use pen and paper, or perhaps simple mechanical aids...
, 91-shiki injiki (九一式印字機) ("System 91 Printing Machine") or Angōki Taipu-A (暗号機 タイプA) ("Type A Cipher Machine"), codenamed Red by the United States, was a diplomatic cryptographic machine used by the Japanese Foreign Office before and during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. A relatively simple device, it was quickly broken by western cryptographers. The Red cipher was succeeded by the "Purple" machine ("97-shiki ōbun inji-ki") which used some of the same principles. Parallel usage of the two systems assisted in the breaking of the Purple system.
The Red cypher should not be confused with the Red naval code, which was used by the Imperial Japanese Navy
Imperial Japanese Navy
The Imperial Japanese Navy was the navy of the Empire of Japan from 1869 until 1947, when it was dissolved following Japan's constitutional renunciation of the use of force as a means of settling international disputes...
between the wars. The latter was a codebook
Codebook
A codebook is a type of document used for gathering and storing codes. Originally codebooks were often literally books, but today codebook is a byword for the complete record of a series of codes, regardless of physical format.-Cryptography:...
system, not a cipher.
Operation
The Red machine encrypted and decrypted texts written in Latin characters (alphabetic only) for transmission through the cable services. These services charged a lower rate for texts that could be pronounced than for random strings of characters; therefore the machine produced telegraph codeTelegraph code
A telegraph code is a character encoding used to transmit information through telegraphy machines. The most famous such code is Morse code.-Manual telegraph codes:Morse code can be transmitted and received with very primitive equipment....
by encyphering the vowel
Vowel
In phonetics, a vowel is a sound in spoken language, such as English ah! or oh! , pronounced with an open vocal tract so that there is no build-up of air pressure at any point above the glottis. This contrasts with consonants, such as English sh! , where there is a constriction or closure at some...
s separately from the consonant
Consonant
In articulatory phonetics, a consonant is a speech sound that is articulated with complete or partial closure of the vocal tract. Examples are , pronounced with the lips; , pronounced with the front of the tongue; , pronounced with the back of the tongue; , pronounced in the throat; and ,...
s, so that the text remained a series of syllables. (The letter "Y" was treated as a vowel.) The "sixes and twenties" effect (as American analysts referred to it) was a major weakness which the Japanese continued in the Purple system.
Encryption itself was provided through a single half-rotor; input contacts were through slip ring
Slip ring
A slip ring is a method of making an electrical connection through a rotating assembly. Slip rings, also called rotary electrical interfaces, rotating electrical connectors, collectors, swivels, or electrical rotary joints, are commonly found in electric motors, electrical generators for AC...
s, each of which connected to a single output contact on the rotor. Since both the vowels and consonants were passed through the same rotor, it had sixty contacts (the least common multiple
Least common multiple
In arithmetic and number theory, the least common multiple of two integers a and b, usually denoted by LCM, is the smallest positive integer that is a multiple of both a and b...
of six and twenty); wiring ensured that the two groups were kept separate. The slip rings were connected to the input keyboard through a plugboard
Plugboard
A plugboard, or control panel , is an array of jacks, or hubs, into which patch cords can be inserted to complete an electrical circuit. Control panels were used to direct the operation of some unit record equipment...
; again this was organized to keep the vowels and consonants separate.
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. The irregular pattern of rotation produced an Alberti cipher
Alberti cipher
- Leon Battista Alberti :Created in the 15th century , it was the peak of cryptography at that time. Its inventor was Leon Battista Alberti, an illegitimate son of an Italian nobleman. He was also interested in painting and writing, though he is probably best known for his architecture...
.
History
The vulnerability of Japanese code systems was made public in 1931 when Herbert YardleyHerbert Yardley
Herbert Osborne Yardley was an American cryptologist best known for his book The American Black Chamber . The title of the book refers to the Cipher Bureau, the cryptographic organization of which Yardley was the founder and head...
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
Washington Naval Conference
The Washington Naval Conference also called the Washington Arms Conference, was a military conference called by President Warren G. Harding and held in Washington from 12 November 1921 to 6 February 1922. Conducted outside the auspices of the League of Nations, it was attended by nine nations...
. These revelations prompted Japanese to look into machine cyphers.
The system was introduced in 1930-1931 (the 91 in the designation refers to the Japanese Imperial Year 2591), using a reverse-engineered
Reverse engineering
Reverse engineering is the process of discovering the technological principles of a device, object, or system through analysis of its structure, function, and operation...
version of a machine supplied by the firm of Boris Hagelin
Boris Hagelin
Boris Caesar Wilhelm Hagelin was a Swedish businessman and inventor of encryption machines.Born of Swedish parents in the Caucasus , Hagelin attended Lundsberg boarding school and later studied mechanical engineering at the Royal Institute of Technology in Stockholm, graduating in 1914...
. Hagelin's most sophisticated systems were rotor machine
Rotor machine
In cryptography, a rotor machine is an electro-mechanical device used for encrypting and decrypting secret messages. Rotor machines were the cryptographic state-of-the-art for a prominent period of history; they were in widespread use in the 1920s–1970s...
s similar to those used in World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, but as he did not trust the Japanese to honor his patent
Patent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....
s, he sent a more primitive device designed by Arvid Damm
Arvid Gerhard Damm
Arvid Gerhard Damm was a Swedish engineer and inventor. He designed a number of cipher machines, and was one of the early inventors of the wired rotor principle for machine encipherment. His company, AB Cryptograph, was a predecessor of Crypto AG....
instead. 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.
The code was broken successfully by three independently working groups. The British solution came first, with Hugh Foss
Hugh Foss
Hugh Rose Foss was a British cryptographer.-Life:Foss was born in Kobe, Japan, where his father the Rt Revd Hugh Foss was a missionary bishop, and he learned Japanese....
and Oliver Strachey
Oliver Strachey
Oliver Strachey , a British civil servant in the Foreign Office was a cryptographer from World War I to World War II....
working out the code in 1934, and Harold Kenworthy's shop producing a replica, the "J machine", a year later. American attempts to break the system waited until 1935. In the Army SIS
Signals Intelligence Service
The Signals Intelligence Service was the United States Army codebreaking division, headquartered at Arlington Hall. It was a part of the Signal Corps so secret that outside the office of the Chief Signal officer, it did not officially exist. William Friedman began the division with three "junior...
group, the system was broken by Frank Rowlett
Frank Rowlett
Frank Byron Rowlett was an American cryptologist.Rowlett was born in Rose Hill, Virginia and attended Emory & Henry College in Emory, Virginia, where he was a member of the Beta Lambda Zeta fraternity. In 1929 he received a bachelor's degree in mathematics and chemistry...
and Solomon Kullback
Solomon Kullback
Solomon Kullback was an American cryptanalyst and mathematician, who was one of the first three employees hired by William F. Friedman at the US Army's Signal Intelligence Service in the 1930s, along with Frank Rowlett and Abraham Sinkov. He went on to a long and distinguished career at SIS and...
; for the navy, Agnes Driscoll is generally credited. (She actually solved the Orange (or M-1) cipher used by naval attaches, but as it turned out the two systems were essentially the same.) The Americans also constructed a replica machine to expedite solutions; interestingly, this machine had two half-rotors to solve the vowels and consonants separately. The SIS group originally referred to it simply as the "Japanese code machine", but decided that so descriptive a term was a security risk; as it was the first Japanese machine cipher solved, they decided to start at the beginning of the spectrum, and named it "RED".
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. This was one of many deficiencies in Japanese use of encryption that helped make the PURPLE system vulnerable to cracking, for now there was some identical traffic on both systems, which allowed cribbing. 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
Tripartite Pact
The Tripartite Pact, also the Three-Power Pact, Axis Pact, Three-way Pact or Tripartite Treaty was a pact signed in Berlin, Germany on September 27, 1940, which established the Axis Powers of World War II...
between the Axis powers. Reports of the sea trial
Sea trial
A sea trial is the testing phase of a watercraft . It is also referred to as a "shakedown cruise" by many naval personnel. It is usually the last phase of construction and takes place on open water, and can last from a few hours to many days.Sea trials are conducted to measure a vessel’s...
s of the battleship
Battleship
A battleship is a large armored warship with a main battery consisting of heavy caliber guns. Battleships were larger, better armed and armored than cruisers and destroyers. As the largest armed ships in a fleet, battleships were used to attain command of the sea and represented the apex of a...
Nagato
Japanese battleship Nagato
Nagato was a battleship of the Imperial Japanese Navy; the lead ship of her class. She was the first battleship in the world to mount 16 inch guns, her armour protection and speed made her one of the most powerful capital ships at the time of her commissioning.She was the flagship of Admiral...
were also decoded, leading to important changes to the USS North Carolina (BB-55)
USS North Carolina (BB-55)
USS North Carolina was the lead ship of her class of battleship and the fourth in the United States Navy to be named in honor of this U.S. state. She was the first new-construction U.S. battleship to enter service during World War II, participating in every major naval offensive in the Pacific...
, then being designed, in order to match the performance of the Japanese ship.
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 cypher.