Hebern rotor machine
Encyclopedia
The Hebern Rotor Machine was an electro-mechanical encryption
machine built by combining the mechanical parts of a standard typewriter
with the electrical parts of an electric typewriter, connecting the two through a scrambler. It is the first example (though just barely) of a class of machines known as rotor machine
s that would became the primary form of encryption during World War II
and for some time after, and which included such famous examples as the German
Enigma.
was a building contractor who was jailed in 1908 for stealing a horse. It is claimed that, with time on his hands, he started thinking about the problem of encryption, and eventually devised a means of mechanizing the process with a typewriter. At the time he had no funds to be able to spend time working on such a device, but he dusted off his thinking in 1917, built a sample, and patented it in 1918. Agnes Driscoll
, the chief civilian employee of the US Navy's cryptography operation (later to become OP-20-G
) between WWI
and WWII
, spent some time working with Hebern before returning to Washington and OP-20-G in the mid-'20s.
Hebern was so convinced of the future success of the system that he formed the Hebern Electric Code company with money from several investors. Over the next few years he repeatedly tried to sell the machines both to the US Navy
and Army
, as well as to commercial interests such as banks. None was terribly interested, as at the time cryptography was not widely considered important outside governments. It was probably because of William F. Friedman
's confidential analysis of the Hebern machine's weaknesses (substantial, though repairable) that its sales to the US government were so limited; Hebern was never told of them. Perhaps the best indication of a general distaste for such matters was the statement by Henry Stimson in his memoirs that "gentlemen should not read each other's mail". It was Stimson, as Secretary of State under Hoover, who withdrew State Department support for Herbert Yardley
's American Black Chamber, leading to its closing.
Eventually his investors ran out of patience, and sued Hebern for stock manipulation. He spent another brief period in jail, but never gave up on the idea of his machine. In 1931 the Navy finally purchased several systems, but this was to be his only real sale.
There were three other patents for rotor machines issued in 1919, and several other rotor machines were designed independently at about the same time. The most successful and widely used was the Enigma machine
.
When the user pressed a key on the typewriter keyboard, a small amount of current from a battery flowed through the key into one of the contacts on the input side of the disk, through the wiring, and back out a different contact. The power then operated the mechanicals of an electric typewriter to type the encrypted letter, or alternately simply lit a bulb or paper tape punch from a teletype machine.
Normally such a system would be no better than the single-alphabet systems of the 16th century. However the rotor in the Hebern machine was geared to the keyboard on the typewriter, so that after every keypress, the rotor turned and the substitution alphabet thus changed slightly. This turns the basic substitution into a polyalphabetic one similar to the well known Vigenère cipher
, with the exception that it required no manual lookup of the keys or cyphertext. Operators simply turned the rotor to a pre-chosen starting position and started typing. To decrypt the message, they turned the rotor around in its socket so it was "backwards", thus reversing all the substitutions. They then typed in the ciphertext and out came the plaintext.
Better yet, several rotors can be placed such that the output of the first is connected to the input of the next. In this case the first rotor operates as before, turning once with each keypress. Additional rotors are then spun with a cam
on the one beside it, each one being turned one position after the one beside it rotates a full turn. In this way the number of such alphabets increases dramatically. For a rotor with 26 letters in its alphabet, five such rotors "stacked" in this fashion allows for 265 = 11,881,376 different possible substitutions.
William F. Friedman
attacked the Hebern machine soon after it came on the market in the 1920s. He quickly "solved" any machine that was built similar to the Hebern, in which the rotors were stacked with the rotor at one end or the other turning with each keypress, the so-called fast rotor. In these cases the resulting ciphertext consisted of a series of single-substitution cyphers, each one 26 letters long. He showed that fairly standard techniques could be used against such systems, given enough effort.
Of course, this fact was itself a great secret. This may explain why the Army and Navy were unwilling to use Hebern's design, much to his surprise.
Encryption
In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...
machine built by combining the mechanical parts of a standard typewriter
Typewriter
A typewriter is a mechanical or electromechanical device with keys that, when pressed, cause characters to be printed on a medium, usually paper. Typically one character is printed per keypress, and the machine prints the characters by making ink impressions of type elements similar to the pieces...
with the electrical parts of an electric typewriter, connecting the two through a scrambler. It is the first example (though just barely) of a class of machines known as 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 that would became the primary form of encryption 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...
and for some time after, and which included such famous examples as the German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
Enigma.
History
Edward Hugh HebernEdward Hebern
Edward Hugh Hebern was an early inventor of rotor machines, devices for encryption.-Background:Edward Hugh Hebern was born in Streator, Illinois on April 23, 1869. His parents were Charles and Rosanna Hebern. They met in Harris County, Texas while Charles was serving as guard and escort from the...
was a building contractor who was jailed in 1908 for stealing a horse. It is claimed that, with time on his hands, he started thinking about the problem of encryption, and eventually devised a means of mechanizing the process with a typewriter. At the time he had no funds to be able to spend time working on such a device, but he dusted off his thinking in 1917, built a sample, and patented it in 1918. Agnes Driscoll
Agnes Meyer Driscoll
Agnes Meyer Driscoll was, known as Miss Aggie or Madame X, an Americancryptanalyst during both World War I and World War II.-Early years:...
, the chief civilian employee of the US Navy's cryptography operation (later to become OP-20-G
OP-20-G
OP-20-G or "Office of Chief Of Naval Operations , 20th Division of the Office of Naval Communications, G Section / Communications Security", was the US Navy's signals intelligence and cryptanalysis group during World War II. Its mission was to intercept, decrypt, and analyze naval communications...
) between WWI
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
and WWII
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...
, spent some time working with Hebern before returning to Washington and OP-20-G in the mid-'20s.
Hebern was so convinced of the future success of the system that he formed the Hebern Electric Code company with money from several investors. Over the next few years he repeatedly tried to sell the machines both to the US Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...
and Army
United States Army
The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...
, as well as to commercial interests such as banks. None was terribly interested, as at the time cryptography was not widely considered important outside governments. It was probably because of William F. Friedman
William F. Friedman
William Frederick Friedman was a US Army cryptographer who ran the research division of the Army's Signals Intelligence Service in the 1930s, and parts of its follow-on services into the 1950s...
's confidential analysis of the Hebern machine's weaknesses (substantial, though repairable) that its sales to the US government were so limited; Hebern was never told of them. Perhaps the best indication of a general distaste for such matters was the statement by Henry Stimson in his memoirs that "gentlemen should not read each other's mail". It was Stimson, as Secretary of State under Hoover, who withdrew State Department support for Herbert Yardley
Herbert 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...
's American Black Chamber, leading to its closing.
Eventually his investors ran out of patience, and sued Hebern for stock manipulation. He spent another brief period in jail, but never gave up on the idea of his machine. In 1931 the Navy finally purchased several systems, but this was to be his only real sale.
There were three other patents for rotor machines issued in 1919, and several other rotor machines were designed independently at about the same time. The most successful and widely used was the Enigma machine
Enigma machine
An Enigma machine is any of a family of related electro-mechanical rotor cipher machines used for the encryption and decryption of secret messages. Enigma was invented by German engineer Arthur Scherbius at the end of World War I...
.
Description
The key to the Hebern design was a disk with electrical contacts on either side, known today as a rotor. Linking the contacts on either side of the rotor were wires, with each letter on one side being wired to another on the far side in a random fashion. The wiring encoded a single substitution alphabet.When the user pressed a key on the typewriter keyboard, a small amount of current from a battery flowed through the key into one of the contacts on the input side of the disk, through the wiring, and back out a different contact. The power then operated the mechanicals of an electric typewriter to type the encrypted letter, or alternately simply lit a bulb or paper tape punch from a teletype machine.
Normally such a system would be no better than the single-alphabet systems of the 16th century. However the rotor in the Hebern machine was geared to the keyboard on the typewriter, so that after every keypress, the rotor turned and the substitution alphabet thus changed slightly. This turns the basic substitution into a polyalphabetic one similar to the well known Vigenère cipher
Vigenère cipher
The Vigenère cipher is a method of encrypting alphabetic text by using a series of different Caesar ciphers based on the letters of a keyword. It is a simple form of polyalphabetic substitution....
, with the exception that it required no manual lookup of the keys or cyphertext. Operators simply turned the rotor to a pre-chosen starting position and started typing. To decrypt the message, they turned the rotor around in its socket so it was "backwards", thus reversing all the substitutions. They then typed in the ciphertext and out came the plaintext.
Better yet, several rotors can be placed such that the output of the first is connected to the input of the next. In this case the first rotor operates as before, turning once with each keypress. Additional rotors are then spun with a cam
Cam
A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion or vice-versa. It is often a part of a rotating wheel or shaft that strikes a lever at one or more points on its circular path...
on the one beside it, each one being turned one position after the one beside it rotates a full turn. In this way the number of such alphabets increases dramatically. For a rotor with 26 letters in its alphabet, five such rotors "stacked" in this fashion allows for 265 = 11,881,376 different possible substitutions.
William F. Friedman
William F. Friedman
William Frederick Friedman was a US Army cryptographer who ran the research division of the Army's Signals Intelligence Service in the 1930s, and parts of its follow-on services into the 1950s...
attacked the Hebern machine soon after it came on the market in the 1920s. He quickly "solved" any machine that was built similar to the Hebern, in which the rotors were stacked with the rotor at one end or the other turning with each keypress, the so-called fast rotor. In these cases the resulting ciphertext consisted of a series of single-substitution cyphers, each one 26 letters long. He showed that fairly standard techniques could be used against such systems, given enough effort.
Of course, this fact was itself a great secret. This may explain why the Army and Navy were unwilling to use Hebern's design, much to his surprise.