Enigma machine
On the 23rd of February 1918, German engineer Arthur Scherbius applied for a patent covering a ciphering machine that used rotating disks. He and E. Richard Ritter founded the firm Scherbius & Ritter to develop this technology further. The company approached both the German Navy and Foreign Office with their design in the early years following World War I. Neither agency showed interest in purchasing the device at that time. Scherbius & Ritter then assigned the patent rights to Gewerkschaft Securitas on the 9th of July 1923. This group established Chiffriermaschinen Aktien-Gesellschaft to market the finished product under the brand name Enigma. The first commercial model appeared in 1923 as the Enigma Handelsmaschine. It was heavy and bulky, measuring 65 by 45 by 38 centimeters and weighing approximately 70 kilograms. Early versions lacked the reflector component found in later military models. They required manual switching between enciphering and deciphering modes. A typewriter attachment made the Schreibende Enigma model from 1924. Problems with the printer construction persisted until 1926. The Glühlampenmaschine or glow lamp version introduced a reflector suggested by colleague Willi Korn. This model used light bulbs instead of paper output and cost one-eighth the price of its predecessor. Commercial sales expanded to countries including Sweden, the Netherlands, Japan, Italy, Spain, and Poland. By 1927, the Enigma D model became widely distributed internationally.
Hans-Thilo Schmidt provided German cipher materials to French intelligence during September and October 1932. These documents included daily keys containing plugboard settings that had been compromised. Marian Rejewski, a Polish mathematician working at the Cipher Bureau, received this material through French channels. He applied permutation theory to solve for unknown rotor wiring configurations. Rejewski utilized message traffic from late 1932 to reconstruct the internal connections of the machine. His team built their own replicas called Enigma doubles to test hypotheses about the device. Fellow cryptologists Jerzy Różycki and Henryk Zygalski joined him in this effort after recruitment from Poznań University. Their work enabled reading of German Enigma messages starting in January 1933. The Polish Cipher Bureau developed techniques to defeat the plugboard and identify all components of daily keys. They exploited quirks of the rotors to compile catalogues with 100,000 entries. Rejewski invented a cyclometer to assist in creating these comprehensive lists. The team also produced Zygalski sheets and electromechanical devices known as bomby. By 1938, Poland operated six bomby machines to search for rotor settings. When Germany added two more rotors that same year, ten times as many units would have been required to maintain decryption capabilities. This mathematical approach allowed pre-war intelligence gathering before the conflict began.
On July 26th and 27th 1939, representatives met at Pyry just south of Warsaw to share decryption methods. Polish officials initiated French and British military intelligence into their Enigma reconstruction techniques. They provided equipment including Zygalski sheets and the cryptologic bomb machine. Each delegation received a Polish-reconstructed Enigma device shortly after the meeting. British Military Mission 4 arrived in September 1939 to evacuate key personnel from Poland. Colin Gubbins and Vera Atkins led this mission intending to extract Marian Rejewski, Jerzy Różycki, and Henryk Zygalski. Their superiors had already evacuated the cryptologists into Romania where they resumed work. Security protocols forced the Cipher Bureau to deliberately destroy records and equipment during departure. The mathematicians traveled onward to France to collaborate with British counterparts. A team of seven Spanish cryptographers known as Equipo D joined the effort under Antonio Camazón. These specialists worked alongside Polish analysts at the PC Bruno centre near Paris. Their tasks included manual decryption and rotor setting reconstruction for Western Allies. Gordon Welchman later wrote that Hut 6 Ultra would never have started without learning details from the Poles. The transfer formed the crucial basis for subsequent World War II British efforts at Bletchley Park.
Three intact Enigma cipher machines belonging to German Army and Air Force forces were captured during the Norwegian campaign between April 8th and the 10th of June 1940. Operations began on the 17th of May 1940 at the British intelligence center located at Bletchley Park. Gordon Welchman became head of Hut 6 where decrypted messages were processed daily. The intelligence derived from these sources received the codename Ultra within Allied command structures. British cryptologists decrypted vast numbers of messages enciphered using the machine throughout the war period. German procedural flaws and operator mistakes enabled success despite cryptographic weaknesses in design. Captured key tables and hardware provided additional advantages to codebreakers working in Hut 6. The Abwehr used different versions including a model with no plugboard introduced during Operation Torch in November 1942. This particular machine had three rotors rotating eleven, fifteen, and nineteen times instead of once per twenty-six letters. A plate on the left acted as a fourth rotor that changed rotation patterns significantly. The Abwehr code was broken by Dilly Knox on the 8th of December 1941. Agents sent messages through simple codes which were then transmitted via Enigma encryption. Breaking this simpler system allowed operation of the Double-Cross System against German agents. From October 1944 onward, the Abwehr utilized Schlüsselgerät 41 machines in limited quantities.
Current flows from battery through depressed bi-directional keyboard switch into plugboard connections before entering entry wheel. The signal passes through wiring inside three or four installed rotors depending on variant type. It enters reflector unit which returns current back through rotors via entirely different path. Plug S connects with cable leading to plug D before reaching another switch to light appropriate lamp. Each rotor contains one or more notches controlling stepping motion when keys are pressed. Right-hand rotor steps once with every keystroke while other rotors step less frequently. Turnover occurs when notch aligns with pawl allowing engagement with ratchet mechanism. Double-stepping affects middle rotor only if ratchet engages during movement forward. This causes deviation from odometer-style regular motion creating period of sixteen thousand nine hundred combinations. Rotors measure approximately ten centimeters diameter made from Ebonite or Bakelite material. Brass spring-loaded electrical contacts arrange in circle on one face with corresponding plates on opposite side. Twenty-six wires connect each pin to contact inside body forming complex pattern. Most rotors identified by Roman numerals I through V all wired identically within same model. Special thin beta and gamma rotors used in M4 naval variant differ slightly from standard types. Four-rotor Naval Enigma accommodates extra rotor replacing original reflector with thinner version.
Operator sets machine according to secret settings shared across network including Grundstellung position AOH visible through windows. He chooses arbitrary starting position like EIN for message encryption session then types it twice producing encrypted indicator XHTLOA. Transmission includes first six letters before operator turns rotors to actual message setting EIN. Receiving operator sets initial position AOH and types first six characters yielding EINEIN on lamps revealing message setting. This procedure contained two weaknesses exploited by Polish Cipher Bureau beginning in 1932. First weakness involved global initial position meaning all keys used same polyalphabetic substitution repeatedly. Second problem stemmed from repetition of indicator creating relation between first fourth second fifth third sixth character pairs. Later procedures avoided double-encoded message settings but introduced new vulnerabilities over time. Navy codebooks printed red water-soluble ink on pink paper allowed easy destruction if vessel sunk. Messages limited to two hundred fifty characters maximum length divided into parts using different keys. Wehrmacht replaced comma with ZZ and question mark with FRAGE or FRAQ abbreviations. Kriegsmarine substituted Y for comma and UD for question mark instead. Combination CH became Q representing words like Acht or Richtung shortened to AQT or RIQTUNG. Two three four zeros converted to CENTA MILLE MYRIA respectively during transmission. Groups counted five characters for Army Air Force while Navy used four-character groupings throughout operations.
Effort to break Enigma remained undisclosed until 1973 when public interest began growing significantly. Machines now appear on display at museums worldwide including Deutsches Museum Munich and Bletchley Park National Codes Centre. Private collectors hold several units alongside computer history enthusiasts seeking operational examples. Prices range from forty thousand dollars up to five hundred forty-seven thousand five hundred euros in recent auctions. Christie's sold an M4 model used by Karl Dönitz to unidentified buyer for four hundred eighty-two thousand six hundred euros in November 2025. Rare Abwehr machine designated G312 stolen from Bletchley Park museum on the 1st of April 2000 returned anonymously after ransom demand. Blackmailer sent note demanding twenty-five thousand pounds threatening destruction if unpaid. Machine arrived missing three rotors before parts recovered through investigation of antiques dealer Dennis Yates sentenced October 2001. Twenty-eight machines discovered attic Madrid headquarters helped Franco Nationalists win Spanish Civil War despite British breaking cipher in 1937. Some displayed Spanish military museums including National Museum Science Technology La Coruña and Spanish Army Museum. Two given Britain GCHQ while Bulgarian military used Cyrillic keyboard variant exhibited Sofia National Museum Military History.
Common questions
When did Arthur Scherbius apply for the Enigma machine patent?
Arthur Scherbius applied for a patent covering a ciphering machine that used rotating disks on the 23rd of February 1918. He and E. Richard Ritter founded the firm Scherbius & Ritter to develop this technology further.
How did Polish mathematicians break the Enigma code before World War II?
Marian Rejewski received German cipher materials from French intelligence in September and October 1932 to reconstruct internal connections using permutation theory. His team built replicas called Enigma doubles, invented a cyclometer, and produced Zygalski sheets to defeat plugboard settings by January 1933.
What happened at Pyry during July 1939 regarding Enigma decryption methods?
Polish representatives met with French and British military intelligence at Pyry just south of Warsaw on July 26th and 27th 1939 to share decryption techniques. They provided equipment including Zygalski sheets and cryptologic bomb machines to each delegation before security protocols forced the Cipher Bureau to destroy records.
When were intact Enigma machines captured during the Norwegian campaign?
Three intact Enigma cipher machines belonging to German Army and Air Force forces were captured between April 8th and the 10th of June 1940. Operations began on the 17th of May 1940 at the British intelligence center located at Bletchley Park where decrypted messages received the codename Ultra.
How does the signal flow through an Enigma machine rotor system?
Current flows from battery through depressed bi-directional keyboard switch into plugboard connections before entering entry wheel and passing through wiring inside three or four installed rotors. The signal enters reflector unit which returns current back through rotors via entirely different path before reaching another switch to light appropriate lamp.