Frequently Asked Questions

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Did the Germans ever suspect that Enigma had been broken?

Not really. Whilst the Germans introduced improvements to the cipher security of the Enigma before and during the War, there was an optimistic belief in the impenetrability of the code. There were times that the security of German communications was brought into question, but the Allies took particular care to protect their codebreaking operation and to safeguard the use of intelligence gained from broken Enigma messages. For more information, a good book on this subject is 'The Ultra Secret', by F. W. Winterbotham.

How can I find out more about cryptologic history?

There are plenty of good print and online resources concerning the history of cryptology. For online resources, see Useful Links for a selection of good websites to learn more. You can also join the International Conference on Cryptologic History (ICCH), a group of collectors, experts and enthusiasts. The group has an email list hosted on and meets every two weeks for online presentations on a range of cryptologic topics. Membership of ICCH is free and open to everyone.

How many Enigma machines were produced and how many still survive?

It is not entirely clear how many Enigma machines were produced due to the lack of surviving records. There are a number of different Enigma models to take into account. But if you just consider the standard three-rotor Enigma I machine, used by the German Wehrmacht and Luftwaffe, some estimates can be made. Statistical analysis of surviving serial numbers, a method employed by the Allies during the Second World War to estimate German tank production numbers, suggests that just over 20,000 Enigma I machines were produced. This matches the estimate made by the Allied Target Intelligence Committee (TICOM), which states that about 30,000 Enigma machines equipped with plugboards (the Enigma I and naval Enigma machines) were produced. Today, over 400 Enigma machines of all models are known to survive in museum and private collections around the world. See David Hamer's List of Surviving Enigmas for more information. Although this is not an obligation, machines are still being added to this list and there are still some yet to be found.

Were Enigma machines used after the Second World War?

Yes, Enigma machines were used by some government agencies in the post-war period. Whilst many were destroyed, a significant quantity of Enigma machines were captured at the end of the War and later sold alongside other surplus wartime equipment. Examples of post-war users of the Enigma machine include the Norwegian Police Security Service, the Bundesgrenzschutz (the West German Federal Border Guard) and also the Italian Guardia di Finanzia (Financial Police), which used them as late as 1985. In the aftermath of the War, some captured Enigma machines were offered by the British to their former colonies, including 30 machines to Israel. The offer of these machines had an ulterior motive. Given that the breaking of the Enigma during the War remained a secret, offering Enigma machines allowed the British to tap the communications of these countries. The Swiss, who had used a variant of the Enigma K between 1938 and 1946, also used the machine for a second time in the 1950s, in the early years of their mission in Korea monitoring the armistice line between North and South Korea.

You can learn more about the use of Enigma machines in the years following the Second World War in Dr Mark Baldwin’s article ‘Did Britain sell Enigmas postwar?'

What is the difference between a cipher machine and a cipher device?

Whilst both are used to encode or decode cipher text, the term 'cipher machine' is typically used to describe a system involving mechanical apparatus whilst the term 'cipher device' is used to describe manual systems. For example, the Hagelin M-209B (which uses wheels, pins and lugs to adjust its setting) is classed as a cipher machine. On the other hand, the British Slidex (a paper-based, manual cipher system) is classed as a cipher device.

What was the British equivalent to the German Enigma machine?

The British Typex cipher machine, developed in 1934, was based on the design of the commercial Enigma machine. The Typex exhibits similarity in function to the Enigma machine, such as also being a rotor-based cipher machine, but has a number of advantages. These advantages include a greater number of rotors, multiple turnover notches, a non-reciprocal plugboard, and being more efficient to operate. Regarding the latter advantage, it has a built-in printer so can be operated by a single person and can be attached to a teleprinter. As few captured Enigma machines were available during the war, Typex machines were employed by British codebreakers (with some modifications) as 'Enigma Doubles' — as simulators of the Enigma machine.