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 German military. The Enigma machine was considered so secure that it was used to encipher the most top-secret messages.

The Enigma has an electromechanical rotor mechanism that scrambles the 26 letters of the Latin alphabet. In typical use, one person enters text on the Enigma's keyboard and another person writes down which of the 26 lights above the keyboard illuminated at each key press. If plaintext is entered, the illuminated letters are the ciphertext. Entering ciphertext transforms it back into readable plaintext. The rotor mechanism changes the electrical connections between the keys and the lights with each keypress.

For the system to be bidirectional, the receiving station would have to know and use the exact settings employed by the transmitting station to decrypt a message. This consisted of a series of initial settings that were generally changed daily, based on secret key lists distributed in advance. Despite the seeming difficulty in decrypting its messages, Enigma contained a number of design issues that left patterns in the cyphertext. Poland first cracked the machine as early as December 1932 and was able to read messages prior to and into the war. Poland's sharing of their achievements enabled the Allies to exploit Enigma-enciphered messages as a major source of intelligence.

History

The Enigma machine was invented by German engineer Arthur Scherbius at the end of World War I. The German firm Scherbius & Ritter, co-founded by Scherbius, patented ideas for a cipher machine in 1918 and began marketing the finished product under the brand name Enigma in 1923, initially targeted at commercial markets. Early models were used commercially from the early 1920s, and adopted by military and government services of several countries, most notably Nazi Germany before and during World War II.

Several Enigma models were produced, but the German military models, having a plugboard, were the most complex. Japanese and Italian models were also in use. With its adoption (in slightly modified form) by the German Navy in 1926 and the German Army and Air Force soon after, the name Enigma became widely known in military circles. Pre-war German military planning emphasised fast, mobile forces and tactics, later known as blitzkrieg, which depended on radio communication for command and coordination. Since adversaries would likely intercept radio signals, messages had to be protected with secure encipherment. Compact and easily portable, the Enigma machine filled that need.

Breaking Enigma

Main article: Cryptanalysis of the Enigma

Hans-Thilo Schmidt was a German who spied for the French, obtaining access to German cipher materials that included the daily keys used in September and October 1932. Those keys included the plugboard settings. The French passed the material to Poland. Around December 1932, Marian Rejewski, a Polish mathematician and cryptologist at the Polish Cipher Bureau, used the theory of permutations, and flaws in the German military-message encipherment procedures, to break message keys of the plugboard Enigma machine. Rejewski was aided by fellow mathematician-cryptologists Jerzy Różycki and Henryk Zygalski, both of whom had been recruited with Rejewski from Poznań University. The Polish Cipher Bureau developed techniques to defeat the plugboard and find all components of the daily key, which enabled the Cipher Bureau to read German Enigma messages starting from January 1933.

On 26 and 27 July 1939, in Pyry, just south of Warsaw, the Poles initiated French and British military intelligence representatives into the Polish Enigma-decryption techniques and equipment, including Zygalski sheets and the cryptologic bomb, and promised each delegation a Polish-reconstructed Enigma (the devices were soon delivered).

During the war, British cryptologists decrypted a vast number of messages enciphered on Enigma. The intelligence gleaned from this source, codenamed "Ultra" by the British, was a substantial aid to the Allied war effort.

Though Enigma had some cryptographic weaknesses, in practice it was German procedural flaws, operator mistakes, failure to systematically introduce changes in encipherment procedures, and Allied capture of key tables and hardware that, during the war, enabled Allied cryptologists to succeed.

Design

The Enigma machine was a cipher device used to protect important messages during World War II. It looked like a keyboard with lamps underneath and used rotating parts called rotors to scramble letters. When someone pressed a key, the rotors turned and changed the path of an electrical current. This made each letter turn into a different letter, creating a secret code.

The machine had several parts that worked together to make the code harder to break. The keyboard sent signals through wires inside the machine. These signals passed through the rotors, which changed them, and then lit up lamps to show the coded letter. The rotors could be set in many different ways, making the code very complex and difficult to solve without knowing the exact settings.

Operation

The Enigma machine was a special tool used to send secret messages during World War II. A person would type a message on the machine, and each letter would light up as a different letter. This made the message hard to read because no one knew how the letters changed unless they had the same machine set up exactly the same way.

To use the Enigma correctly, both the person sending the message and the person receiving it had to set their machines the same way. This included choosing the order of parts inside the machine, how they were positioned, and which letters were connected. Because there were so many ways to set up the machine, it was very hard to break the code, making Enigma seem very secure.

Models

The Enigma machine was a cipher device with several models developed over time. The earliest versions were commercial machines from the early 1920s. Later, the German military adopted and modified Enigma for their communications, making it a key part of their encryption during World War II. An estimated 40,000 Enigma machines were made.

The first commercial Enigma, called Enigma Handelsmaschine, was introduced in 1923. It used a typewriter for input and output. Later models, such as the Enigma A and Enigma B, used glow lamps instead of a typewriter, making them cheaper and more reliable. Military versions, like the Enigma I, added features such as a plugboard to increase security. The German Navy used a four-rotor version called M4 starting in 1942 to protect U-boat communications. Various countries, including Italy and Japan, also used different Enigma models for their own needs.

Surviving machines

Enigma machines, once secret devices used in World War II, are now on display in museums around the world. The Deutsches Museum in Munich and the Deutsches Spionagemuseum in Berlin both show these historic machines. Other places where you can see Enigmas include the National Codes Centre in Bletchley Park, the Science Museum in London, and many others in countries such as Spain, Norway, Denmark, and Australia.

In the United States, Enigma machines can be found at the Computer History Museum in Mountain View, California and the National Cryptologic Museum in Fort Meade, Maryland. Some museums even let visitors try encoding and decoding messages. Over the years, some Enigmas have been sold at auctions for very high prices.

Derivatives

The Enigma machine inspired the creation of other cipher machines. After learning how the Enigma worked, the British developed a similar machine called the Typex. They built it without paying for the Enigma patents. In the United States, a cryptologist named William Friedman designed a machine called the M-325 that worked in a comparable way.

Other machines like the SIGABA and NEMA were also made, but they function differently from the Enigma. In 2002, a person named Tatjana van Vark in the Netherlands built a special rotor machine with 40-point rotors that could handle letters, numbers, and some punctuation.

Simulators

Main article: List of Enigma machine simulators

There are many tools and websites that let people try out how the Enigma machine worked. These simulators help us understand the clever ways messages were hidden during World War II. By using them, anyone can see how difficult it was to break the codes made by the Enigma machine.