The ABC of cryptography: masterpieces of encryption
Private and confidential? How people made cryptography more and more secure – and how the codes were cracked time and time again.
By Deutsches Museum
Deutsches Museum
Just between us: cryptic secrets
Confidential messages not intended for anyone else's eyes or ears—even children play around with enciphering by creating their own secret code at school that only the addressee can figure out and no one else. People have been working with the principles of encryption for over 3,000 years, starting in Egypt and Mesopotamia when they simply replaced their familiar symbols with others. From the 15th century, text was encrypted using the polyalphabetic system, whereby a letter could be substituted with more than one character. The best-known apparatus is probably the Enigma, a device used during the Second World War—its name is now synonymous with encryption machines.
Video zur ChriffrierscheibeDeutsches Museum
The secret of the turntable
The grid turntable is rotated to positions one through 4 in order. Each of its letters is then read from the top left to reveal any secret messages…
Chiffrierstäbchen (1500)Deutsches Museum
The cipher rods
Monoalphabetic encryption was particularly common up to the 15th century. This involved substituting letters with other set characters, e.g., an A is always substituted with a D, a B with a W, a C with an M, etc. With polyalphabetic encryption, however, letters could be substituted with more than one letter, as with the cipher rods here. An A could now be a D in one word, but a K in the next. As with all other systems through to modern times, the sender and receiver need to have previously agreed on the methodology of the secret language.
Der Automatische Kryptograf von Alexis Køhl (1895)Deutsches Museum
The automatic cryptograph
In 2013, a random find in a warehouse turned out to be the oldest encryption machine in the Deutsches Museum. This so-called cryptograph by Danish engineer Alexis Køhl (1846–1920) was sent by the inventor himself in 1918 from Copenhagen to the Deutsches Museum, along with the announcement that he would soon travel to Munich to talk about his device. Unfortunately this trip never took place, as Køhl fell ill and died shortly after. We now know that Køhl constructed his device at the end of the 19th century.
The principle involved pushing metal rods into their holes on the outer ring, which were aligned with the plain text letters on the inner ring.
Similarly to a typewriter, this moved the levers arranged in a circle inside a funnel underneath this golden disc. They then printed letters in the secret code onto a sheet of paper stretched under the blue ribbon seen here.
Mechanische Chiffriermaschine Kryha (1920)Deutsches Museum
The Kryha machine
Stylish exterior and sophisticated design: although this machine by the Ukrainian Alexander von Kryha looked elegant, its security was less impressive. Experts quickly figured out the encryption principle.
Mechanische Chiffriermaschine Kryha Standard (1920)Deutsches Museum
In 1933, American William F. Friedmann and his cryptologist team cracked a Kryha-encrypted message with 1,135 characters in under 2 hours and 41 minutes.
Die C-Maschine von Boris Hagelin (1925)Deutsches Museum
Boris Hagelin's machines
Boris Hagelin from Sweden was the first cryptologist to become a millionaire by developing encryption machines. In the 1920s, he started work on his prototype B-21, and later developed the C-36 (pictured). The M-209, the improved follow-up model, was equipped with 6 coding wheels instead of 5 and became an instant hit. Hagelin sold 140,000 units to the US Army.
Ansicht der Enigma (1918)Deutsches Museum
The Enigma
The most famous cipher machine in the world is probably the Enigma. The invention of the working principle used in the Enigma stems from pioneers such as American building contractor Edward Hugh Hebern (1869–1952), who invented a rotating device for machine encryption in 1917. In 1918, Frankfurt engineer Arthur Scherbius (1878–1929) patented the rotor principle. He created the Enigma machine—named after the Greek word for "riddle"—in his cipher machine workshop in Berlin, introducing it in Bern in 1923 and to the public at the Postal Union Congress in Stockholm in 1924.
Ansicht der Enigma (1918)Deutsches Museum
After Scherbius's death in 1929, the Enigma's technical development was headed by Willi Korn. Government interest in these machines was initially low worldwide. In Germany, the Reichswehr took over the Enigma. Widespread armaments were carried out after Hitler seized power in 1933, and the Enigma was part of this program. Although its various models were used the most during the Second World War, the Enigma was not the only encryption machine the German authorities had available. Strategic messages were encrypted using even more complex devices.
If it doesn't work, check the battery if needed—the most important piece of advice for using the Enigma!
Aufbau der Enigma (1930)Deutsches Museum
Constructing the Enigma
A model blueprint from 1928 shows exactly how the Enigma was constructed…
…from its retaining levers to its spring buttons and reserve bulbs.
Each time a button was pressed, the rotors rotated one more step. When it comes to the way it works, it's best to imagine it as a mechanical tachometer. After a full rotation of rotor A, rotor B rotates one position further. And in turn, after a complete rotation of rotor B, rotor C moves one more step.
As part of this process, 3–4 rotors were always selected from a set of 5–8 and used in a newly defined order each time. The initial rotor setting was also continually redefined. When the machines were used during the Second World War, the different settings were changed at least once a day.
Die Enigma geöffnet (1918)Deutsches Museum
For many years, the Enigma was considered to be "uncrackable." Figuring out the system and deciphering the encrypted messages appeared to be impossible. But wasn't the Titanic also considered to be unsinkable? In Bletchley Park, a country estate in the idyllic county of Buckinghamshire, cryptanalysts of the Government Code and Cypher School worked at and finally succeeded in deciphering the cipher codes used not just by the Enigma, but also by other machines employed by the Germans such as the Lorenz encryption machine and Siemens T52 Geheimschreiber, ("secret teleprinter").
Tap to explore
Today, the Bletchley Park museum is a popular destination for locals and tourists who want to learn more about how the German cipher machines were decoded. The Enigma itself became a rarity. It is believed that only around 150 units survived the Second World War, and just a handful can be found in museums worldwide. A private collector paid $365,000 US dollars for one machine when it was auctioned off in New York in 2015.
Die Stiftwalzen-Chiffriermaschine (1950)Deutsches Museum
The pinwheel cipher machine
Of course, after the end of the Second World War, encryption devices continued to be refined. Here we can see the Swedish HC-9 pinwheel cipher machine by Transvertex from 1950. It was not only portable but also programmable.
Video zur HC-9 TransvertexDeutsches Museum
Here, Swedish cryptologist Lars Larsson explains how the HC-9 works in the Deutsches Museum in 2017.
Alphanumerisches Taschenterminal (1976)Deutsches Museum
DDT 300 U7 cipher terminal
This looked like it came from a secret workshop run by Q, the inventor in the James Bond movies.
The DDT 300 U7 cipher terminal, contained in an inconspicuous aluminum briefcase, could code, transmit, and receive messages in the late 1970s. To transfer messages, a telephone handset was held against the earpieces provided. This sent audio signals only but no spoken words. Conveniently, the accompanying encryption and transmission device fitted into a black leather cigarette case.
Krypto-Telefon P-171D-ATS (1970)Deutsches Museum
Honecker's secret device
This crypto-telephone by the Russian company Telta—the P-171D-ATS—was used in the former German Democratic Republic for secret discussions, allegedly by Erich Honecker himself. The KGB used similar devices. Variants without a dial, which were used to connect to headquarters directly, were also common.
Video zum Venom-PrinzipDeutsches Museum
The one-time pad
The one-time pad, a concept by American cryptographer Frank Miller (1842–1925) which was later refined and patented by fellow American and engineer Gilbert Vernam (1890–1969), was also groundbreaking. A key feature is its one-off use of a random key which is at least as long as the message to be encrypted. When used correctly with a truly random one-time key, this method is unbreakable—and this can be proven mathematically. During the Cold War, the one-time pad also kept the Red Telephone secure: the hotline between the US President and the Soviet General Secretary.
Simulation Ausstellungsräume ab 2019Deutsches Museum
The future
Here's an initial impression of the large, modern cryptography exhibition that will be open to visitors from 2019 with a brand-new look on the 4th floor of the Deutsche Museum. One very special exhibit is…
Die Hitler-Mühle (1941)Deutsches Museum
Die SG-41
A sensational find: In May 2017, two amateur treasure hunters found an SG-41 encryption device, known as the "Hitler mill" because of its side crank, in a wood in Aying south of Munich.
Das Schlüsselgerät SG-41 (1941)Deutsches Museum
The SG-41 was even more advanced and secure than the Enigma. While the British specialists in Bletchley Park were able to crack the Enigma and the Lorenz encryption machine, they were stumped by the SG-41. That's why they called this device a "mystery."
Created by Deutsches Museum.
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