John R. F. Jeffreys
Encyclopedia
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
mathematician
Mathematician
A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....
and World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
codebreaker
Codebreaker
Codebreaker may refer to:*A person who performs cryptanalysis*The Codebreakers, a 1967 book on history of cryptography by David Kahn*Codebreaker , a 1981 puzzle-based computer game, originally released for the Atari 2600...
.
A research fellow
Research fellow
The title of research fellow is used to denote a research position at a university or similar institution, usually for academic staff or faculty members. A research fellow may act either as an independent investigator or under the supervision of a principal investigator...
at Downing College, Cambridge, Jeffreys joined the codebreaking efforts at Bletchley Park
Bletchley Park
Bletchley Park is an estate located in the town of Bletchley, in Buckinghamshire, England, which currently houses the National Museum of Computing...
in September 1939 alongside fellow Cambridge mathematicians Gordon Welchman
Gordon Welchman
Gordon Welchman was a British-American mathematician, university professor, World War II codebreaker at Bletchley Park, and author.-Education and early career:...
, with whom he had previously worked closely, and Alan Turing
Alan Turing
Alan Mathison Turing, OBE, FRS , was an English mathematician, logician, cryptanalyst, and computer scientist. He was highly influential in the development of computer science, providing a formalisation of the concepts of "algorithm" and "computation" with the Turing machine, which played a...
. These three, together with Peter Twinn
Peter Twinn
Peter Frank George Twinn was a British mathematician, World War II codebreaker and entomologist.-Education and codebreaking:...
and working under Dilly Knox
Dilly Knox
Alfred Dillwyn 'Dilly' Knox CMG was a classics scholar at King's College, Cambridge, and a British codebreaker...
, formed the research section working on the German Enigma machine
Enigma machine
An Enigma machine is any of a family of related electro-mechanical rotor cipher machines used for the encryption and decryption of secret messages. Enigma was invented by German engineer Arthur Scherbius at the end of World War I...
, and were housed in "The Cottage" at Bletchley Park.
Jeffreys was put in charge of a small section manufacturing perforated sheets for use in the cryptanalysis of the Enigma
Cryptanalysis of the Enigma
Cryptanalysis of the Enigma enabled the western Allies in World War II to read substantial amounts of secret Morse-coded radio communications of the Axis powers that had been enciphered using Enigma machines. This yielded military intelligence which, along with that from other decrypted Axis radio...
, a task which took over three months, completed on 7 January 1940. One type were the Zygalski sheets, known as Netz at Bletchley Park, a technique revealed to the British by Polish cryptologists. Another type, named "Jeffreys sheets", were different, and were a "catalogue of the effect of any two Enigma rotors and the reflector". Jeffreys's perforated sheets were used by Polish cryptologists in exile in France to make the first wartime decryption of an Enigma message on 17 January 1940.
In early 1940, a section called "Hut 6
Hut 6
Hut 6 was a wartime section of Bletchley Park tasked with the solution of German Army and Air Force Enigma machine ciphers. Hut 8, by contrast, attacked Naval Enigma...
" — named after the building in which it was initially housed — was created to work on solving German Army and Air Force Enigma messages. Jeffreys was chosen to run the hut alongside Welchman. Jeffreys was in charge of "Sheet-Stacking and Machine Room activities", while Welchman handled "Registration, Intercept Control, Decoding, and relations with the intelligence people in Hut 3".
In May 1940, Jeffreys took a vacation, but became ill and was diagnosed with tuberculosis
Tuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...
and diabetes. He died in March 1944.
Gordon Welchman later recalled:
- "Jeffreys was very much liked at Bletchley Park. His death was a tragic loss to all of us. We felt deep sympathy for his fianceé, Pat Hempsted, who had been a member of his team from its beginnings in the Cottage. She was involved both in the initial punching of the sheets and in the testing of drops on which our early breaks depended."