Editing Rotor machine (section)

==History==

===Invention===
{{citation needed|reason=section|date=February 2017}}
The concept of a rotor machine occurred to a number of inventors independently at a similar time.

In 2003, it emerged that the first inventors were two [[Royal Netherlands Navy|Dutch naval officers]], Theo A. van Hengel (1875–1939) and R. P. C. Spengler (1875–1955) in 1915 (De Leeuw, 2003). Previously, the invention had been ascribed to four inventors working independently and at much the same time: [[Edward Hebern]], [[Arvid Damm]], [[Hugo Koch]] and [[Arthur Scherbius]].

In the [[United States]] [[Edward Hugh Hebern]] built a rotor machine using a single rotor in 1917. He became convinced he would get rich selling such a system to the military, the [[Hebern Rotor Machine]], and produced a series of different machines with one to five rotors. His success was limited, however, and he went [[bankrupt]] in the 1920s. He sold a small number of machines to the [[US Navy]] in 1931.

In Hebern's machines the rotors could be opened up and the wiring changed in a few minutes, so a single mass-produced system could be sold to a number of users who would then produce their own rotor keying. Decryption consisted of taking out the rotor(s) and turning them around to reverse the circuitry. Unknown to Hebern, [[William F. Friedman]] of the [[United States Army|US Army]]'s [[Signals Intelligence Service|SIS]] promptly demonstrated a flaw in the system that allowed the ciphers from it, and from any machine with similar design features, to be cracked with enough work.

Another early rotor machine inventor was Dutchman [[Hugo Koch]], who filed a [[patent]] on a rotor machine in 1919. At about the same time in [[Sweden]], [[Arvid Gerhard Damm]] invented and patented another rotor design. However, the rotor machine was ultimately made famous by [[Arthur Scherbius]], who filed a rotor machine patent in 1918. Scherbius later went on to design and market the [[Enigma machine]].

===The Enigma machine===
{{main article|Enigma machine}}
[[File:EnigmaMachineLabeled.jpg|thumbnail|right|A German Enigma machine]]
The most widely known rotor cipher device is the German [[Enigma machine]] used during World War II, of which there were a number of variants.

The standard Enigma model, Enigma I, used three rotors. At the end of the stack of rotors was an additional, non-rotating disk, the "reflector," wired such that the input was connected electrically back out to another contact on the same side and thus was "reflected" back through the three-rotor stack to produce the [[ciphertext]].

When current was sent into most other rotor cipher machines, it would travel through the rotors and out the other side to the lamps. In the Enigma, however, it was "reflected" back through the disks before going to the lamps.  The advantage of this was that there was nothing that had to be done to the setup in order to decipher a message; the machine was "symmetrical".

The Enigma's reflector guaranteed that no letter could be enciphered as itself, so an ''A'' could never turn back into an ''A''. This helped Polish and, later, British efforts to break the cipher. (''See'' [[Cryptanalysis of the Enigma]].)

Scherbius joined forces with a mechanical engineer named Ritter and formed Chiffriermaschinen AG in [[Berlin]] before demonstrating Enigma to the public in [[Bern]] in 1923, and then in 1924 at the World Postal Congress in [[Stockholm]]. In 1927 Scherbius bought Koch's patents, and in 1928 they added a ''plugboard'', essentially a non-rotating manually rewireable fourth rotor, on the front of the machine. After the death of Scherbius in 1929, [[Willi Korn]] was in charge of further technical development of Enigma.

As with other early rotor machine efforts, Scherbius had limited commercial success. However, the German armed forces, responding in part to revelations that their codes had been broken during World War I, adopted the Enigma to secure their communications. The ''[[Reichsmarine]]'' adopted Enigma in 1926, and the [[Reichswehr|German Army]] began to use a different variant around 1928.

The Enigma (in several variants) was the rotor machine that Scherbius's company and its successor, Heimsoth & Reinke, supplied to the German military and to such agencies as the Nazi party security organization, the ''[[Sicherheitsdienst|SD]]''.

The [[Poland|Poles]] broke the German Army Enigma beginning in December 1932, not long after it had been put into service. On July 25, 1939, just five weeks before Hitler's invasion of Poland, the [[Polish General Staff]]'s [[Polish Cipher Bureau|Cipher Bureau]] shared its Enigma-decryption methods and equipment with the French and British as the Poles' contribution to the common defense against Nazi Germany. [[Dilly Knox]] had already broken Spanish Nationalist messages on a commercial Enigma machine in 1937 during the [[Spanish Civil War]].

A few months later, using the Polish techniques, the British began reading Enigma ciphers in collaboration with [[Polish Cipher Bureau]] cryptologists who had escaped Poland, overrun by the Germans, to reach [[Paris]]. The Poles  continued breaking German Army Enigma—along with [[Luftwaffe]] Enigma traffic—until work at Station ''[[PC Bruno]]'' in France was shut down by the German invasion of May–June 1940.

The British continued breaking Enigma and, assisted eventually by the United States, extended the work to German Naval Enigma traffic (which the Poles had been reading before the war), most especially to and from [[U-boat]]s during the [[Battle of the Atlantic]].

===Various machines===
[[File:Enigma rotor.jpg|thumb|right|The rotor stack from an Enigma rotor machine. The rotors of this machine contain 26 contacts.]]
During [[World War II]] (WWII), both the Germans and Allies developed additional rotor machines. The Germans used the [[Lorenz SZ 40/42]] and [[Siemens and Halske T52]] machines to encipher teleprinter traffic which used the [[Baudot code]]; this traffic was known as [[Fish (cryptography)|Fish]] to the Allies. The Allies developed the [[Typex]] (British) and the [[SIGABA]] (American). During the War the [[Switzerland|Swiss]] began development on an Enigma improvement which became the [[NEMA machine]] which was put into service after World War II. There was even a Japanese developed variant of the Enigma in which the rotors sat horizontally; it was apparently never put into service. The Japanese [[PURPLE]] machine was not a rotor machine, being built around electrical [[stepping switch]]es, but was conceptually similar.

Rotor machines continued to be used even in the computer age. The [[KL-7]] (ADONIS), an encryption machine with 8 rotors, was widely used by the U.S. and its allies from the 1950s until the 1980s. The last [[Canada|Canadian]] message encrypted with a KL-7 was sent on June 30, 1983. The Soviet Union and its allies used a 10-rotor machine called [[Fialka]] well into the 1970s.

[[Image:Typex nocase.jpg|thumbnail|right|Typex was a printing rotor machine used by the United Kingdom and its Commonwealth, and was based on the Enigma patents.]]
[[File:SIGCUM.jpg|thumb|The U.S. SIGCUM was a  five rotor system used to encrypt teletype traffic.]]
A unique rotor machine called the Cryptograph was constructed in 2002 by [[Netherlands]]-based Tatjana van Vark. This unusual device is inspired by Enigma, but makes use of 40-point rotors, allowing letters, numbers and some punctuation; each rotor contains 509 parts.

A software implementation of a rotor machine was used in the [[crypt (Unix)|crypt]] command that was part of early [[Unix|UNIX]] operating systems. It was among the first software programs to run afoul of [[Export of cryptography#Cold War era|U.S. export regulations]] which classified [[cryptographic]] implementations as munitions.