CHAPTER 10

The Enigma machine

joel greenberg

S

hortly after the end of the First World War, the German Navy learned that its encrypted

communications had been read throughout the hostilities by both Britain and Russia.

The German military realized that its approach to cipher security required a fundamen-

tal overhaul, and from 1926 different branches of the military began to adopt the encryption

machine known as Enigma. By the start of the Second World War a series of modifications to

military Enigma had made the machine yet more secure, and Enigma was at the centre of a

remarkably effective military communications system. It would take some of the best minds

in Britain—and before that, in Poland—to crack German military Enigma.^1

Introduction

The exact origins of the encryption machine that played such an important role in the Second

World War are not entirely clear.^2 In the early 1920s patent applications for a wheel-based

cipher machine were filed by a Dutch inventor, Hugo Koch, as well as by a German engineer,

Arthur Scherbius.

In 1923, a company called Chiffrienmaschinen AG exhibited a heavy and bulky encryp-

tion machine at the International Postal Congress in Bern, Switzerland. This machine had a

standard typewriter keyboard for input, and its design followed Scherbius’s original patent

closely. Scherbius had named his machine ‘Enigma’, and this ‘Model A’ was the first of a long

line of models to emerge. Models B, C, and D soon followed, and by 1927 Model D was selling

widely for commercial use. A number of governments purchased Enigma machines in order

to study them, and Edward Travis—the deputy head of Britain’s signals intelligence unit, the

Government Code and Cypher School—bought one on behalf of the British government in the

mid-1920s.

In 1925, the German Navy decided to put Enigma into use the following year, despite having

rejected one of Scherbius’s previous encryption mechanisms in 1918. Meanwhile, the German

Army began to redesign Enigma, with the intention of strengthening its security. By 1928,

Model G was in use,^3 and in June 1930 Model I (Eins) became the standard version, deployed

first by the army, then the navy in October 1934, and the air force in August 1935.