Editing Enigma machine (section)

== Models ==
The Enigma family included multiple designs. The earliest were commercial models dating from the early 1920s. Starting in the mid-1920s, the German military began to use Enigma, making a number of security-related changes. Various nations either adopted or adapted the design for their own cipher machines.

{|style="margin: 1em auto 0 auto;"
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| [[File:Enigmas.jpg|upright=2.0|thumb|A selection of seven Enigma machines and paraphernalia exhibited at the U.S. [[National Cryptologic Museum]]. From left to right, the models are: 1) Commercial Enigma; 2) Enigma T; 3) Enigma G; 4) Unidentified; 5) ''Luftwaffe'' (Air Force) Enigma; 6) ''Heer'' (Army) Enigma; 7) ''Kriegsmarine'' (Naval) Enigma&nbsp;— M4.]]
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An estimated 40,000 Enigma machines were constructed.{{sfn|Bauer|2000|p=123}}<ref>[https://cryptocellar.org/enigma/e-history/enigma-reichswehr-wehrmacht-orders.pdf ''Reichswehr and Wehrmacht Enigma Orders''] {{Webarchive|url=https://web.archive.org/web/20210629133408/https://cryptocellar.org/enigma/e-history/enigma-reichswehr-wehrmacht-orders.pdf |date=29 June 2021 }} in Frode Weierud’s CryptoCellar, accessed 29&nbsp;June 2021.</ref> After the end of World War II, the Allies sold captured Enigma machines, still widely considered secure, to developing countries.{{sfn|Bauer|2000|p=112}}

=== Commercial Enigma ===
[[File:Scherbius-1928-patent.png|thumb|right|upright=1.45|Scherbius Enigma patent, {{US patent|1657411}}, granted in 1928]]
On 23 February 1918,<ref>{{cite web| url = https://www.cdvandt.org/Enigma%20DE416219C1.pdf| title = German patent No. 416219 from 23 February 1918}}</ref> [[Arthur Scherbius]] applied for a [[patent]] for a ciphering machine that used [[rotor machine|rotors]].<ref>{{cite patent |inventor-last=Scherbius |inventor-first=Arthur |title=Ciphering Machine |country-code=US |patent-number=1657411 |gdate=24 January 1928 |pridate=11 February 1922 |fdate=6 February 1923 |assign1=Chiffriermaschinen AG}}</ref> Scherbius and [[E. Richard Ritter]] founded the firm of Scherbius & Ritter. They approached the [[Reichsmarine|German Navy]] and Foreign Office with their design, but neither agency was interested. Scherbius & Ritter then assigned the patent rights to Gewerkschaft Securitas, who founded the ''Chiffriermaschinen Aktien-Gesellschaft'' (Cipher Machines Stock Corporation) on 9 July 1923; Scherbius and Ritter were on the board of directors.

==== Enigma Handelsmaschine (1923) ====
Chiffriermaschinen AG began advertising a rotor machine, ''Enigma Handelsmaschine'', which was exhibited at the Congress of the [[Universal Postal Union|International Postal Union]] in 1924. The machine was heavy and bulky, incorporating a [[typewriter]]. It measured 65×45×38&nbsp;cm and weighed about {{convert|50|kg|lb}}.

==== Schreibende Enigma (1924) ====
This was also a model with a type writer. There were a number of problems associated with the printer and the construction was not stable until 1926. Both early versions of Enigma lacked the reflector and had to be switched between enciphering and deciphering.

==== Glühlampenmaschine, Enigma A (1924) ====
The reflector, suggested by Scherbius' colleague Willi Korn,<ref name="Korn">{{cite book |last1=De Leeuw |first1=Karl Maria Michael |last2=Bergstra |first2=J A |title=The history of information security : a comprehensive handbook |date=2007 |publisher=Elsevier |location=Amsterdam |isbn=9780080550589 |page=393}}</ref> was introduced with the glow lamp version.

The machine was also known as the military Enigma. It had two rotors and a manually rotatable reflector. The typewriter was omitted and glow lamps were used for output. The operation was somewhat different from later models. Before the next key pressure, the operator had to press a button to advance the right rotor one step.

==== Enigma B (1924) ====
[[File:Enigma-Glühlämpchen.jpg|thumb|upright|Typical glowlamps (with flat tops), as used for Enigma]]
Enigma ''model B'' was introduced late in 1924, and was of a similar construction.<ref>{{cite web|url=http://www.armyradio.com/publish/Articles/The_Enigma_Code_Breach/Pictures/enigma_type_b.jpg|title=image of Enigma Type B|url-status=dead|archive-url=https://web.archive.org/web/20051021083422/http://www.armyradio.com/publish/Articles/The_Enigma_Code_Breach/Pictures/enigma_type_b.jpg|archive-date=21 October 2005}}</ref> While bearing the Enigma name, both models ''A'' and ''B'' were quite unlike later versions: They differed in physical size and shape, but also cryptographically, in that they lacked the reflector. This model of Enigma machine was referred to as the Glowlamp Enigma or ''Glühlampenmaschine'' since it produced its output on a lamp panel rather than paper. This method of output was much more reliable and cost effective. Hence this machine was 1/8th the price of its predecessor.<ref name="Enigma History"/>

==== Enigma C (1926) ====
''Model C'' was the third model of the so-called ″glowlamp Enigmas″ (after A and B) and it again lacked a typewriter.<ref name="Enigma History"/>

==== Enigma D (1927) ====
The ''Enigma C'' quickly gave way to ''Enigma D'' (1927). This version was widely used, with shipments to Sweden, the Netherlands, United Kingdom, Japan, Italy, Spain, United States and Poland. In 1927 [[Hugh Foss]] at the British [[Government Communications Headquarters|Government Code and Cypher School]] was able to show that commercial Enigma machines could be broken, provided suitable cribs were available.<ref>Bletchley Park Trust Museum display</ref> Soon, the Enigma D would pioneer the use of a standard keyboard layout to be used in German computing.  This "QWERTZ" layout is very similar to the American [[QWERTY]] keyboard format used in many languages.

===== "Navy Cipher D" =====
Other countries used Enigma machines. The [[Italian Navy]] adopted the commercial Enigma as "Navy Cipher D". The Spanish also used commercial Enigma machines during their [[Spanish Civil War|Civil War]]. British codebreakers succeeded in breaking these machines, which lacked a plugboard.{{sfn|Smith|2006|p=23}} Enigma machines were also used by diplomatic services.

==== Enigma H (1929) ====
[[File:Enigma-8-rotor.jpg|right|thumb|upright|A rare 8-rotor printing Enigma model H (1929)]]
There was also a large, eight-rotor printing model, the ''Enigma H'', called ''Enigma II'' by the ''[[Reichswehr]]''. In 1933 the Polish Cipher Bureau detected that it was in use for high-level military communication, but it was soon withdrawn, as it was unreliable and jammed frequently.{{sfn|Kozaczuk|1984|p=28}}

==== Enigma K ====
The Swiss used a version of Enigma called ''Model K'' or ''Swiss K'' for military and diplomatic use, which was very similar to commercial [[#Enigma D (1927)|Enigma D]]. The machine's code was cracked by Poland, France, the United Kingdom and the United States; the latter code-named it INDIGO. An ''Enigma T'' model, code-named ''Tirpitz'', was used by Japan.

=== Military Enigma ===
The various services of the [[Wehrmacht]] used various Enigma versions, and replaced them frequently, sometimes with ones adapted from other services. Enigma seldom carried high-level strategic messages, which when not urgent went by courier, and when urgent went by other cryptographic systems including the [[Geheimschreiber]].

==== Funkschlüssel C ====
The Reichsmarine was the first military branch to adopt Enigma. This version, named ''Funkschlüssel C'' ("Radio cipher C"), had been put into production by 1925 and was introduced into service in 1926.{{sfn|Kahn|1991|pp=39–41, 299}}

The keyboard and lampboard contained 29 letters&nbsp;— A-Z, Ä, Ö and Ü&nbsp;— that were arranged alphabetically, as opposed to the QWERTZUI ordering.{{sfn|Ulbricht|2005|p=4}} The rotors had 28 contacts, with the letter ''X'' wired to bypass the rotors unencrypted.{{sfn|Stripp|1993}} Three rotors were chosen from a set of five{{sfn|Kahn|1991|pp=40, 299}} and the reflector could be inserted in one of four different positions, denoted α, β, γ and δ.{{sfn|Bauer|2000|p=108}} The machine was revised slightly in July 1933.{{sfn|Stripp|1993|loc=plate 3}}

==== Enigma G (1928–1930) ====
By 15 July 1928,{{sfn|Kahn|1991|pp=41, 299}} the German Army (''[[Reichswehr]]'') had introduced their own exclusive version of the Enigma machine, the ''Enigma G''.

The ''[[Abwehr]]'' used the ''Enigma G''. This Enigma variant was a four-wheel unsteckered machine with multiple notches on the rotors. This model was equipped with a counter that incremented upon each key press, and so is also known as the "counter machine" or the ''Zählwerk'' Enigma.

==== Wehrmacht Enigma I (1930–1938) ====
Enigma machine G was modified to the ''Enigma I'' by June 1930.{{sfn|Kruh|Deavours|2002|p=97}} Enigma I is also known as the ''Wehrmacht'', or "Services" Enigma, and was used extensively by German military services and other government organisations (such as the [[Deutsche Reichsbahn#Deutsche Reichsbahn-Gesellschaft (1924-1937)|railways]]{{sfn|Smith|2000|p= 73}}) before and during [[World War II]].

[[File:Bundesarchiv Bild 101I-769-0229-10A, Frankreich, Guderian, "Enigma" cropped.jpg|thumb|upright|[[Heinz Guderian]] in the [[Battle of France]], with an Enigma machine. Note one soldier is keying in text while another writes down the results.]]
The major difference between ''Enigma I'' (German Army version from 1930), and commercial Enigma models was the addition of a plugboard to swap pairs of letters, greatly increasing cryptographic strength.

Other differences included the use of a fixed reflector and the relocation of the stepping notches from the rotor body to the movable letter rings. The machine measured {{convert|28|x|34|x|15|cm|in|abbr=on}} and weighed around {{convert|12|kg|lb|abbr=on}}.{{sfn|Stripp|1993|p=83}}

In August 1935, the Air Force introduced the Wehrmacht Enigma for their communications.{{sfn|Kruh|Deavours|2002|p=97}}

==== M3 (1934) ====
By 1930, the Reichswehr had suggested that the Navy adopt their machine, citing the benefits of increased security (with the plugboard) and easier interservice communications.{{sfn|Kahn|1991|p=43}} The Reichsmarine eventually agreed and in 1934<ref>{{harvnb|Kahn|1991|p=43}} says August 1934. {{harvnb|Kruh|Deavours|2002|p=15}} say October 2004.</ref> brought into service the Navy version of the Army Enigma, designated ''Funkschlüssel'' ' or ''M3''. While the Army used only three rotors at that time, the Navy specified a choice of three from a possible five.{{sfn|Kruh|Deavours|2002|p=98}}
[[File:Bundesarchiv Bild 101I-241-2173-09, Russland, Verschlüsselungsgerät Enigma.jpg|thumb|left|Enigma in use on the Russian front]]

==== Two extra rotors (1938) ====
In December 1938, the Army issued two extra rotors so that the three rotors were chosen from a set of five.{{sfn|Kruh|Deavours|2002|p=97}} In 1938, the Navy added two more rotors, and then another in 1939 to allow a choice of three rotors from a set of eight.{{sfn|Kruh|Deavours|2002|p=98}}

==== M4 (1942) ====
{{See also|Cryptanalysis of the Enigma#M4 (German Navy 4-rotor Enigma)}}
A four-rotor Enigma was introduced by the Navy for U-boat traffic on 1 February 1942, called ''[[Cryptanalysis of the Enigma#M4 (German Navy 4-rotor Enigma)|M4]]'' (the network was known as ''Triton'', or ''Shark'' to the Allies). The extra rotor was fitted in the same space by splitting the reflector into a combination of a thin reflector and a thin fourth rotor.

<gallery mode="packed" heights="160">
File:Enigma-G.jpg|Enigma G, used by the ''[[Abwehr]]'', had four rotors, no plugboard, and multiple notches on the rotors.
File:Enigma-IMG 0484-black.jpg|The German-made Enigma-K used by the Swiss Army had three rotors and a reflector, but no plugboard. It had locally re-wired rotors and an additional lamp panel.
File:Four-rotor-enigma.jpg|An Enigma model T (Tirpitz), a modified commercial Enigma K manufactured for use by the Japanese
File:Enigma Decoder Machine.jpg|An Enigma machine in the UK's Imperial War Museum
File:Bundesarchiv Bild 101I-241-2173-06, Russland, Verschlüsselungsgerät Enigma.jpg|Enigma in use in Russia
File:Bundesarchiv Bild 146-2006-0188, Verschlüsselungsgerät "Enigma".jpg|Enigma in radio car of the 7th Panzer Div. staff, August 1941
</gallery>

[[File:CMoA Enigma Machine Exhibit in Georgia.JPG|thumb|A three-rotor Enigma machine on display at [[Mimms Museum of Technology and Art]] and its two additional rotors]]