Polish copy of Enigma made by Biuro Szyfrow

A Polish Enigma "double" was a machine produced by the Polish

Biuro Szyfrów The Cipher Bureau ( Polish: ''Biuro Szyfrów'', ) was the interwar Polish General Staff's Second Department's unit charged with SIGINT and both cryptography (the ''use'' of ciphers and codes) and cryptanalysis (the ''study'' of ciphers and cod ...

that replicated the German

Enigma machine The Enigma machine is a cipher 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 W ...

. The Enigma double was one result of

Marian Rejewski Marian Adam Rejewski (; 16 August 1905 – 13 February 1980) was a Polish people, Polish mathematician and Cryptography, cryptologist who in late 1932 reconstructed the sight-unseen German military Enigma machine, Enigma cipher machine, aided ...

's remarkable achievement of determining the wirings of the Enigma's rotors and reflectors.

First Polish double

The Polish Cipher Bureau realized that the Germans were using a new cipher. The Germans had mistakenly shipped a cipher machine to Poland; their attempts to recover the shipment raised the suspicions of Polish customs, and the Cipher Bureau learned that the Germans were using Enigma machines. The Bureau purchased a commercial Enigma and attempted, but failed, to break the cipher. In December 1932 the Cipher Bureau tasked

with reconstructing the Enigma machine. A French spy had obtained some material about the Enigma, and the French had provided the material to the Polish Cipher Bureau. By then, for the purposes of the German military, the original commercial Enigma had been equipped with a plugboard. Rejewski made rapid progress and was able to determine the wirings of the military Enigma. The Bureau modified its commercial Enigma rotors, reflector, and internal wiring to match the military Enigma's. The Cipher Bureau's commercial Enigma did not have a plugboard, but the plugboard could be simulated by relabeling the keys and lamps. The result was the first Polish Enigma double.

AVA-made doubles

In February 1933, the Polish Cipher Bureau ordered fifteen "doubles" of the military

from the AVA Radio Manufacturing Company, in Warsaw. Ultimately, about seventy such functional replicas were produced.

Gift to Poland's Allies

In August 1939, following a tripartite meeting of Polish, French, and British cryptologists at Warsaw on 25–26 July 1939 – during which the Poles had explained all their Enigma-decryption methods and equipment – two Enigma replicas were passed to Poland's allies, one sent to Paris and one to London. Earlier, German military Enigma traffic had totally defeated the French and British, and they had faced the prospect of being unable to read German communications during the coming war.

Polish doubles assembled in France

After Germany invaded Poland in September 1939 and key Polish Polish Cipher Bureau personnel had been evacuated to

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

, the Cipher Bureau resumed its interrupted work at ''

PC Bruno ''PC Bruno'' was a Polish– French–Spanish signals–intelligence station near Paris during World War II, from October 1939 until June 1940. Its function was decryption of cipher messages, most notably German messages enciphered on the Enigma ...

'' outside

Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...

. The Poles had only three replica Enigmas to work with, two secretly taken out of Poland during the evacuation, and the one that had been sent to France after the July 1939 Warsaw conference, and these were wearing out from round-the-clock use.

French Army The French Army, officially known as the Land Army (, , ), is the principal Army, land warfare force of France, and the largest component of the French Armed Forces; it is responsible to the Government of France, alongside the French Navy, Fren ...

intelligence officer An intelligence officer is a member of the intelligence field employed by an organization to collect, compile or analyze information (known as intelligence) which is of use to that organization. The word of ''officer'' is a working title, not a r ...

Gustave Bertrand Gustave Bertrand (1896–1976) was a French military intelligence officer who made a vital contribution to the decryption, by Poland's Cipher Bureau, of German Enigma ciphers, beginning in December 1932. This achievement would in turn lead t ...

ordered parts for forty machines from a French precision-mechanics firm. Manufacture proceeded sluggishly, however, and it was only after the fall of France and the opening of underground work in southern France's Free Zone in October 1940 that four machines were finally assembled.

Notes

References

* * *

External links

* Slawo Wesolkowski,
The Invention of Enigma and How the Polish Broke It Before the Start of WWII
* http://www.cryptomuseum.com/crypto/enigma/hist.htm has picture of Enigma double (http://www.cryptomuseum.com/crypto/enigma/polish/img/polish_enigma_1.jpg) * http://www.codesandciphers.org.uk/virtualbp/poles/poles.htm has picture of Enigma double {{Authority control Cipher Bureau (Poland) Enigma machine History of cryptography Science and technology in Poland