Ultra

:This article is about WW II intelligence material codenamed "Ultra." For other usages, see Ultra (disambiguation)

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Ultra (sometimes capitalised ULTRA) was the name used by the British for intelligence resulting from decryption of German communications in World War II. The term eventually became the standard designation in both Britain and the United States for all intelligence from high-level cryptanalytic sources. The name arose because the code-breaking success was considered more important than the highest security classification available at the time (Most Secret) and so was regarded as being Ultra Secret.

Related Topics:
British - Decryption - German - World War II - United States - Cryptanalytic

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Much of the German cipher traffic was encrypted on the Enigma machine, hence the term "Ultra" has often been used almost synonymously with "Enigma decrypts."

Related Topics:
Enigma machine - Decrypt

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Until the name "Ultra" was adopted, there were several cryptonyms for intelligence from this source, including Boniface. For some time thereafter, "Ultra" was used only for intelligence from this channel.

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Later the Germans began to use several stream cipher teleprinter systems for their most important traffic, to which the British gave the generic code-name FISH. Several distinct systems were used, principally the Lorenz SZ 40/42 (initially code-named TUNNY) and Geheimfernschreiber (code-named STURGEON).

Related Topics:
Stream cipher - Teleprinter - FISH - Lorenz SZ 40/42 - Geheimfernschreiber

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These also were broken, particularly TUNNY, which the British thoroughly penetrated. It was eventually attacked using the Colossus, considered to be the forerunner of the electronic programmable digital computer. Although the volume of messages read from this system was much smaller than that from the Enigma, they more than made up for it in their importance.

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F.W. Winterbotham, in The Ultra Secret (1974), quotes the western Supreme Allied Commander, Dwight D. Eisenhower, as at war's end describing Ultra as having been "decisive" to Allied victory in World War II.

Related Topics:
F.W. Winterbotham - 1974 - Dwight D. Eisenhower - World War II

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