The Enigma cipher machine

• Simulators
• Allied cryptanalysis
• Cryptanalysis tools
• Turing/Welchman Bombe
• Challenges
• Bertrand's archives
• Enigma Procedures
• Hut 6 story
• Enigma Networks(keys)
• Break a key with Bombe
• My Publications

Introduction

The Enigma is arguably the most famous cipher machine, even my neighbor knows it. Why? We will try to answer this question in this introduction.

The Enigma was designed after World War I. Its principle is simple. You type the message in clear letter after letter. Each time the resulting encrypted letter appears illuminated on a panel above the keyboard. Decryption follows the same logic: we type each letter of the cryptogram and the corresponding clear letters light up.

The first versions of the Enigma were not secret. Embassies, companies could buy it. In 1930 the German army began to use the Enigma but it differs from the public machine because it uses plugs which seem to make the machine unbreakable. The Enigma quickly became the most common means of encryption in the German military forces and was used throughout World War II. About 40,000 Enigma were built.

The allies, mainly France and the UK at the start of the war and then the UK and the US deciphered much of the messages encrypted with the Enigma. In fact decryption had started in 1933. It was the Poles who broke the Enigma. In 1939 they shared their knowledge with the French and the English.

These decipherments undoubtedly had a very important impact on the various battles and may have changed the outcome of the war.

Incredibly, decipherments made by the Allies remained secret until the early 1970s.

Much of the English crypto activity took place at a mansion some 80km from London in Bletchley Park (BP). Once again this place remained secret for decades. It has now become a museum to the glory of English cryptologists. Among them an otherwise well-known mathematician, Alan Turing, is illustrated and was one of the most active in the development of methods to crack the Enigma. In particular, he co-invented a machine, called the "Bombe," which was to be the most important tool for deciphering the Enigma throughout the war.

Here is a summary of the reasons why this machine is now celebrated: the importance of the decipherments carried out by the allies and the secrecy which covered these decipherings for several decades. The mythical figure of Alan Turing and the secrecy surrounding Station-X (BP's code name) added a dose of mystery to this machine.

Hollywood has further amplified its fame, notably with two films: “U-571” and “The Imitation Game”.