Why is the Enigma machine important

Cryptology, cryptography and cryptanalysis

The Enigma cipher machine

The Enigma is a cipher machine that was mainly used during World War II. It was used by the German military to transmit messages. In addition to the military, there were also other institutions that used the Enigma cipher machine for the mostly secret transmission of messages. These were mainly secret services, the police, the SS and the Reichsbahn or Reichspost.

The name "Enigma" comes from the Greek and literally means "riddle".

The Enigma was invented at the time by a German engineer named Arthur Scherbius. In 1918 he applied for the first patent for this cipher machine. In order to be able to produce and manufacture the machine, a stock corporation was founded in 1923. Originally, the Enigma was initially only intended to be used for civil processes and was therefore offered commercially for the first time at trade fairs.

But when the military showed increased interest in the cipher machine in the following years, the Enigma disappeared from the civilian market. After the tragic death of the inventor, the production of the encryption machine was continued under a new company name. At that time, the armament of the military was so advanced that a system that could encrypt and transmit reliable messages was absolutely essential. It is estimated that over 30,000 machines were manufactured during the Second World War, some estimates say that over 200,000 units were produced. The Enigma was produced in several variants and in different models and these were still used after the end of the war. The most used machine was the "Enigma Eins", which was first used by the Reichswehr and later even by the Wehrmacht. This commitment has embodied the Enigma as the most frequently used encryption system.

The Enigma weighed about 10 kg and was about 310 mm long, 255 mm wide and 130 mm high. When you look at this machine, the first thing that comes to mind is a typewriter, since its essential components are a keyboard, a set of rollers and a lamp field for the display. The heart of the machine was the set of rollers. He was responsible for encrypting the data. The roller set consists of three rollers which are rotatably arranged. The rollers were designed so that the letters of the Latin alphabet were on one side and the same number of electrical contacts on the other. These contacts were also connected to the same number of insulated wires that were inside the roller. However, the contacts with the wires were always irregular and connected to one another in pairs. When a letter key is pressed, an electric current flows to a battery located in the machine and this current ensured that the indicator lamp could light up through the set of rollers. The letter that lit up corresponds to the encryption of the letter that was pressed. However, the fact that the reels move further each time a key is pressed, the key alphabet has changed after each individual letter.

So if you had pressed the same letter twice in a row, the lamps always displayed a different letter, caused by the rollers running further. This type of encryption was very important and considered to be cryptographically very valuable. This made it possible to use many different (secret) alphabets.

The structure of the machine is a little difficult to describe in words. The core is certainly the set of rollers. This consists of rotating and non-rotating rollers. The entry roller, which cannot be rotated, connects the contacts of the 26th wires with the respective buttons. On the left side of the roller set is the reversing roller, which is also not rotatable. This roller only had contacts on one side, which are always directly connected to one another in pairs. This roller is responsible for ensuring that the electrical current runs through the roller set from right to left, deflects the current and lets it flow back again from left to right. The current exits again via the entry roller. Overall, the Enigma set of rollers consists of five rotatable rollers and two rollers that cannot be rotated. A board is attached to the front of the device, which is provided with two-pole sockets for the 26 letters. Before the current could flow into the roller set, it was routed through this plug board. If the current finally emerges from the set of rollers, it must also flow through the connector board again, and the purpose of this is to cause the lamp to light up.

The functionality of the Enigma is based on a system of specific electrical circuits. Every single key on the keyboard has been linked to the corresponding indicator light. Pressing a letter key therefore always lights up a new letter. The circuit runs back and forth across the roller contact as if in a loop. If the current is on its way back, the current must flow through the respective plug on the breadboard. The encryption can be varied very well with the help of setting rings on the various rollers. The message could only be decrypted if the recipient had made the same settings on his machine as the sender.

The operators of the encryption machine were pretty sure that the texts they had encrypted could not be decrypted using conventional methods. This assumption was initially confirmed. However, this overlooked the fact that with manual encryption, machine deciphering can be used. In essence, the Enigma was an extraordinarily good and very secure way of conveying messages. The mistake, however, was that the Germans blindly trusted the Enigma's security standard. In retrospect, this turned out to be a very big mistake. The opponents of the Germans managed to completely decipher the code. The whole action to decrypt the Enigma became known under the code name "Ultra". In Poland, a mathematician found out that the Enigma was the main component of German encryption technology. As a result, the Polish military decided in 1928 to set up a department that dealt only with deciphering the encryption machine. The Poles worked on the decryption for several years without getting any noticeable results. It took more than four years for a Polish mathematician to break into the Enigma system.

When sending a message, the cipher selects a rotor starting position and should send it twice in a row. In addition, a new initial setting should be selected for each new message. However, the Germans were so lazy that only one starting position was used all day. As a result, every message transmitted began with the same six letters. The Poles noticed this straight away, and so they quickly figured out that this should be the starting position of the rotors. They got this knowledge because the Enigma was already available for sale in earlier years.

With these and other findings, the Poles have succeeded in deciphering the messages. In 1938 the Germans added two more rotors. As a result, the system of the Enigma became much more complicated, so that the Poles had to grope in the dark again. The Poles realized that the effort to decrypt the system is far too great. The Poles then consulted with a group consisting of French and English to resolve this problem.

In England, on the other hand, the importance of deciphering messages from the Enigma was initially not recognized. The British had a facility that dealt with the decryption of encrypted messages, but only with code books. This facility, in which the messages were deciphered, called itself Betchely Park, but could only develop very moderately due to lack of funds. Another problem was that there weren't enough specialists in the Navy to deal with the matter. By the time the British finally realized the importance and importance of the Enigma, it was almost too late. The English also knew that the Enigma could be bought before the war, but they did not come to the same results as the Poles.

In 1938 the head of the English institution took part in a conference in which the Poles also took part. However, he could not get sufficient insight into the work of the Poles, and then came to the assumption that the Poles had no successes at that time either. It was not until 1939 that the English finally got the records and documentation of the Poles about the Enigma.

In 1940 the mathematician Alan Turing joined the English team. He was the first to succeed in setting up mathematical calculations and theories in order to break into the Enigma system. In collaboration with his colleague Gordon Welchman, he developed the "Turing bomb". The "Turing bomb" was not a bomb in the strict sense of the word, but worked like a machine that deciphered the Enigma's code. There are no invoices or documents about the construction of such "bombs", as the construction was of course top secret. However, the bombs were very large, that is, up to two meters high and five meters wide. The bombs were mostly housed in halls and the women had the task of supervising the bombs. Of course, the women did not know what it was all about, they just had to turn the rotors on the bombs and inform the supervisor if one of the bombs should stop.

Alan Turing even wrote a book about deciphering the Enigma. The book was kept top secret until 1996.

The Germans contributed to a very large extent to the war opponents being able to decipher the Enigma's code. However, the German soldiers came to the aid of the enemy unintentionally. The radio traffic of the German submarine fleet in the Atlantic was transmitted in two ways. On the one hand, the messages were encrypted, on the other hand, the messages were also transmitted in plain text. This was a great advantage and a great help for the English and the Poles, since they now had the messages in plain text and the same texts in ciphertext. This enabled them to determine some properties that were taken into account when choosing the keys.

It is said that there was a radio operator in the German fleet who was so bored that he kept typing the same letter. The English knew that the Enigma did not encrypt a letter with itself and they also knew that the rotors change after each entry. So if someone taps the same letter over and over again, you get a very long chain of different letters that contains all the letters except the one that was typed. Exactly this detail was noticed by an employee in the English unit. However, this only occurs if the radio message consists of only one letter that has been pressed repeatedly. The specialists were now able to see how the Enigma's rotors were set. On several days it even happened that the same basic settings were used. That made the cryptologists' work a lot easier.

Another mistake made by the Germans was that the soldiers used the words "Kaiserreich" and "Vaterland" in almost every radio message. The cryptologists had already suspected this and hired the "native speakers". These are people whose mother tongue is German. These people processed the encrypted radio messages after these words and so it was possible to find out the right key very quickly.

Even after the war, the Enigma still enjoyed a reputation for maximum security. So it was sold to the Middle East and Africa where it was partly used until 1975. Today there are hardly any copies of the Enigma available. Should a machine change hands, there are usually large sums of money involved. In April 2006, for example, an Enigma was sold for € 55,050.

Sources and References