computer science

World War I cryptography

World War I cryptography is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand World War I cryptography rather than just read about it. In short: With the rise of easily intercepted wireless telegraphy, codes and ciphers were used extensively in World War I. The decoding by British Naval intelligence of the Zimmermann telegram helped bring the United States into the war.

Key takeaways

World War I cryptography belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect World War I cryptography to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of World War I cryptography from memory before moving on to harder problems.

Reference excerpt

With the rise of easily intercepted wireless telegraphy, codes and ciphers were used extensively in World War I. The decoding by British Naval intelligence of the Zimmermann telegram helped bring the United States into the war. Trench codes were used by field armies of most of the combatants (Americans, British, French, German) in World War I. The most commonly used codes were simple substitution ciphers. More important messages generally used mathematical encryption for extra security. The use of these codes required the distribution of codebooks to military personnel, which proved to be a security liability since these books could be stolen by enemy forces.

Britain

British decrypting was carried out in Room 40 by the Royal Navy and in MI1 by British Military (Army) Intelligence.

Zimmermann telegram Room 40 Royal Navy (Britain) Alastair Denniston Room 40 James Alfred Ewing Room 40, first head Nigel de Grey Room 40 William R. Hall ‘Blinker’ Hall, Room 40, second head Dilly Knox Room 40 William Montgomery (cryptographer) Room 40 MI1 British Military (Army) Intelligence Malcolm Vivian Hay, MI1(b), head from 1915 Oliver Strachey MI1 Playfair cipher

Russia In the 1914 Battle of Tannenberg, different corps of the Russian Imperial army were unable to decipher each other's messages, so they sent them in plain text. They were easily intercepted. Meanwhile, German cryptanalysts were also able to read the enciphered ones. Ernst Fetterlein was in the Tsarist Russian Ministry of Foreign Affairs from 1896 and solved (among others) German, Austrian and British codes. He became chief cryptographer with the rank of admiral. With the Russian Revolution in 1917 he fled to Britain and was recruited to Room 40 in June 1918 to work on Austrian, Bolshevik and Georgian codes. The Russians used an overcomplicated version of the Vigenère Cipher. It was broken within three days by Austro-Hungarian cryptanalyst Hermann Pokorny.

France The French Army employed Georges Painvin, and Étienne Bazeries who came out of retirement, on German ciphers. Due to their prewar activities, the French were more prepared than any other nation involved in the war to decode German radiograms. At the beginning of the war, France had eight intercept stations: Maubeuge, Verdun, Toul, Epinal, Belfort, Lille, Rheims, and Besançon. During the war, they set up many more stations, including one in the Eiffel Tower. According to Colonel Cartier of the War Ministry, France intercepted over 100,000,000 words from German radiograms during the course of the war.

The Tableau de Concordance was the main French diplomatic cipher.

Germany and Austria-Hungary The Imperial German Army and the Austro-Hungarian Army intercepted Russian radio communications traffic, although German success at the Battle of Tannenberg (1914) was due to interception of messages between the Imperial Russian Army commanders in cleartext. The German Abhorchdienst, a code-breaking bureau composed mainly of mathematicians, was established in 1916. The Germans had specific regulations regarding which kinds of codes and ciphers could be used under given circumstances. Within three kilometers of the front lines, known as the danger zone, all communications were required to be in a code known as the three-number code. This was the only code or cipher permitted. Behind this danger zone, another code known as the three-letter code was allowed to be used. Communications between divisions, corps, and army headquarters were done with the ADFGVX cipher. The ADFGX and ADFGVX field ciphers were a modified polybius system with single order double columnar transposition and frequent key change, with letters optimized for Morse. It was later broken by the famous French cryptanalyst Georges Painvin. The breaking of the ADFGX cipher by Painvin was the second time during the war that cryptanalysis played a major role in shaping events (the first being the interception and cracking of the Zimmerman Telegram). By breaking the cipher, the French were able to decode an intercepted message about the forwarding of munitions for a German offensive, letting the French know where and when the offensive would occur, and thus allowing them to stop it. This message became known as "The Radiogram of Victory."

United States Herbert Yardley began as a code clerk in the State Department. After the outbreak of war he became the head of the cryptographic section of Military Intelligence Section (MI-8) and was with the American Expeditionary Force in World War I as a Signals Corps cryptologic officer in France. He later headed the Cipher Bureau, a new cryptanalysis group started in 1919, immediately after World War I, and funded jointly by the State Department and the US Army. Some American cryptography in World War I was done at the Riverbank Laboratories, Chicago, which was privately owned by Colonel George Fabyan. Elizebeth Friedman, William F. Friedman and Agnes Meyer Driscoll worked there. The US Navy used the cryptographic code A-1. The US Navy cryptanalysis group, OP-20-G, was also started after World War I (in 1922). The US also started employing Indian code talkers in World War I, initially with members of the Cherokee and Choctaw tribes.

See also World War I Cryptography History of cryptography World War II cryptography Japanese cryptology from the 1500s to Meiji

References

External links Online books, and library resources in your library and in other libraries about World War I cryptography

Worked examples

Example 1 — a first encounter with World War I cryptography

Start with the simplest possible case. Write down what World War I cryptography claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to World War I cryptography before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about World War I cryptography ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of World War I cryptography

In research: World War I cryptography appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses World War I cryptography in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: World War I cryptography is common in secondary-school and first-year university syllabi. It links to neighbouring topics History of cryptography, Signals intelligence of World War I, World War I, so understanding it makes those chapters shorter.
In everyday life: Look for World War I cryptography outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study World War I cryptography in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what World War I cryptography means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain World War I cryptography out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is World War I cryptography in simple terms?

Why does World War I cryptography matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study World War I cryptography?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on World War I cryptography.