An Enigma Machine

Arthur Scherbius

An Enigma machine was any of a family of related electro-mechanical rotor cipher machines used in the twentieth century for enciphering and deciphering secret messages. Enigma was invented by the German engineer Arthur Scherbius at the end of World War I.Early models were used commercially from the early 1920s, and adopted by military and government services of several countries most notably by Nazi Germany before and during World War II.Several different Enigma models were produced, but the German military models are the most commonly discussed.

German military texts enciphered on the Enigma machine were first broken by the Polish Cipher Bureau, beginning in December 1932. This success was a result of efforts by three Polish cryptologists, Marian Rejewski, Jerzy Różycki and Henryk Zygalski, working for Polish military intelligence. Rejewski "reverse-engineered" the device, using theoretical mathematics and material supplied by French military intelligence. Subsequently the three mathematicians designed mechanical devices for breaking Enigma ciphers, including the cryptologic bomb. From 1938 onwards, additional complexity was repeatedly added to the Enigma machines, making decryption more difficult and necessitating larger numbers of equipment and personnel more than the Poles could readily produce.

The Enigma was influential in the field of cipher machine design, spinning off other rotor machines. The British Typex was originally derived from the Enigma patents; Typex even includes features from the patent descriptions that were omitted from the actual Enigma machine. The British paid no royalties for the use of the patents, to protect secrecy. The Typex implementation is not the same as that found in German or other Axis versions.

A Japanese Enigma clone was codenamed GREEN by American cryptographers. Little used, it contained four rotors mounted vertically. In the U.S., cryptologist William Friedman designed the M-325, a machine logically similar, although not in construction.

Enigma Machine

A unique rotor machine was constructed in 2002 by Netherlands-based Tatjana van Vark. This device makes use of 40-point rotors, allowing letters, numbers and some punctuation to be used; each rotor contains 509 parts.Machines like the SIGABA, NEMA, Typex and so forth, are deliberately not considered to be Enigma derivatives as their internal ciphering functions are not mathematically identical to the Enigma transform.

Several software implementations exist, but not all exactly match Enigma behavior. The most commonly used software derivative (that is not compliant with any hardware implementation of the Enigma) is at EnigmaCo.de. Many Java applet Enigmas only accept single letter entry, complicating use even if the applet is Enigma compliant. Technically, Enigma@home is the largest scale deployment of a software Enigma, but the decoding software does not implement encipherment making it a derivative (as all original machines could cipher and decipher).

A user-friendly 3-rotor simulator, where users can select rotors, use the plugboard and define new settings for the rotors and reflectors is available. The output appears in separate windows which can be independently made "invisible" to hide decryption.

Enigma Machine With Simple Portable Model

Another includes an "autotyping" function which takes plaintext from a clipboard and converts it to cyphertext (or vice-versa) at one of four speeds. The "very fast" option produces 26 characters in less than one second.