page_title: Enigma machine
section_title: Details
hierarchical_section_title: Enigma machine / Operation / Details
caption_attribution_description: English: A key list for the German Luftwaffe (Air Force) w:Enigma Machines. Translation of text at top:“Secret Command Document! Every individual daily key is secret. Forbidden to bring on aircraft. Luftwaffe Machine Key No.649 Attention! Key material must not fall into enemy hands intact. In case of danger destroy throughly and early." Column contents: Day of month, Rotor order, Ring settings, Jumper plug connections (for reflector and plugboard) and Identifier groups. The presence of jumper settings for the reflector (Umkehrwalze) is an enhancement first observed by the British at the start of 1944.
context_page_description: The Enigma machine is an encryption device developed and used in the early- to mid-20th century to protect commercial, diplomatic and military communication. It was employed extensively by Nazi Germany during World War II, in all branches of the German military.
  Enigma has an electromechanical rotor mechanism that scrambles the 26 letters of the alphabet. In typical use, one person enters text on the Enigma's keyboard and another person writes down which of 26 lights above the keyboard lights up at each key press. If plain text is entered, the lit-up letters are the encoded ciphertext. Entering ciphertext transforms it back into readable plaintext. The rotor mechanism changes the electrical connections between the keys and the lights with each keypress. The security of the system depends on a set of machine settings that were generally changed daily during the war, based on secret key lists distributed in advance, and on other settings that were changed for each message. The receiving station has to know and use the exact settings employed by the transmitting station to successfully decrypt a message.
context_section_description: In use, the Enigma required a list of daily key settings and auxiliary documents. In German military practice, communications were divided into separate networks, each using different settings. These communication nets were termed keys at Bletchley Park, and were assigned code names, such as Red, Chaffinch, and Shark. Each unit operating in a network was given the same settings list for its Enigma, valid for a period of time. The procedures for German Naval Enigma were more elaborate and more secure than those in other services and employed auxiliary codebooks. Navy codebooks were printed in red, water-soluble ink on pink paper so that they could easily be destroyed if they were endangered or if the vessel was sunk.
  An Enigma machine's setting (its cryptographic key in modern terms; Schlüssel in German) specified each operator-adjustable aspect of the machine:
  Wheel order (Walzenlage) – the choice of rotors and the order in which they are fitted.
  Ring settings (Ringstellung) – the position of each alphabet ring relative to its rotor wiring.
  Plug connections (Steckerverbindungen) – the pairs of letters in the plugboard that are connected together.
  In very late versions, the wiring of the reconfigurable reflector.
  Starting position of the rotors (Grundstellung) – chosen by the operator, should be different for each message.
  For a message to be correctly encrypted and decrypted, both sender and receiver had to configure their Enigma in the same way; rotor selection and order, ring positions, plugboard connections and starting rotor positions must be identical. Except for the starting positions, these settings were established beforehand, distributed in key lists and changed daily. For example, the settings for the 18th day of the month in the German Luftwaffe Enigma key list number 649 (see image) were as follows:
  Wheel order: IV, II, V
  Ring settings: 15, 23, 26
  Plugboard connections: EJ OY IV AQ KW FX MT PS LU BD
  Reconfigurable reflector wiring: IU AS DV GL FT OX EZ CH MR KN BQ PW
  Indicator groups: lsa zbw vcj rxn
  Enigma was designed to be secure even if the rotor wiring was known to an opponent, although in practice considerable effort protected the wiring configuration. If the wiring is secret, the total number of possible configurations has been calculated to be around 3×10¹¹⁴ (approximately 380 bits); with known wiring and other operational constraints, this is reduced to around 10²³ (76 bits). Because of the large number of possibilities, users of Enigma were confident of its security; it was not then feasible for an adversary to even begin to try a brute-force attack.
caption: Monthly key list number 649 for the German Air Force Enigma, including settings for the reconfigurable reflector (which only change once every eight days).
exif: {"Image Make": "NIKON CORPORATION", "Image Model": "NIKON D40", "Image Orientation": "Horizontal (normal)", "Image XResolution": "300", "Image YResolution": "300", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Ver.1.10", "Image DateTime": "2008:09:12 15:43:51", "Image YCbCrPositioning": "Co-sited", "Image ExifOffset": "348", "Image CustomRendered": "Normal", "Image ExposureMode": "Auto Exposure", "Image WhiteBalance": "Auto", "Image DigitalZoomRatio": "1", "Image FocalLengthIn35mmFilm": "60", "Image SceneCaptureType": "Standard", "Image GainControl": "Low gain up", "Image Contrast": "Normal", "Image Saturation": "Normal", "Image Sharpness": "Normal", "Image SubjectDistanceRange": "0", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "300", "Thumbnail YResolution": "300", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "30596", "Thumbnail JPEGInterchangeFormatLength": "11920", "Thumbnail YCbCrPositioning": "Co-sited", "EXIF ExposureTime": "1/60", "EXIF FNumber": "9/2", "EXIF ExposureProgram": "Unidentified", "EXIF ISOSpeedRatings": "400", "EXIF ExifVersion": "0221", "EXIF DateTimeOriginal": "2008:09:12 15:43:51", "EXIF DateTimeDigitized": "2008:09:12 15:43:50", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "4", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "43/10", "EXIF MeteringMode": "Pattern", "EXIF LightSource": "Unknown", "EXIF Flash": "Flash fired, auto mode, return light not detected", "EXIF FocalLength": "40", "EXIF SubSecTime": "50", "EXIF SubSecTimeOriginal": "50", "EXIF SubSecTimeDigitized": "50", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "3008", "EXIF ExifImageLength": "2000", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera", "EXIF SceneType": "Directly Photographed", "EXIF CVAPattern": "[0, 2, 0, 2, 2, 1, 1, 0]"}