Joan Clarke
Joan Clarke (Joan Elisabeth Lowther Murray) was an English cryptanalyst, best known for her work on decrypting Nazi Germany’s secret communications during WWII: the Enigma Project.
Featuring artwork & words by Dr. Eleonora Adami, Sci-Illustrate Stories. Set in motion by Dr. Radhika Patnala.
Early years
Joan (Joan Elisabeth Lowther Murray) was born on 24 June 1917 in West Norwood. She attended the Dulwich school for girls in South London and was awarded a scholarship in 1936. This then allowed her to go to Cambridge to study math. In 1939 she obtained a double first degree in mathematics; this was actually just a “title of degree”, since Cambridge only started awarding proper BA degrees to women after 1948.
In 1940, her University supervisor Gordon Welchman, recognizing her abilities, recruited her to work at the Government Code and Cypher School (GCCS) at Bletchley Park and join the codebreakers.
Joan accepted, despite not knowing what the job would exactly entail.
The code-breakers
Thanks to her perseverance and her qualifications, she quickly raised through the ranks and, after joining the staff of Hut 8 at Bletchley, Joan was moved to a room where she interacted directly with Alan Turing and two other cryptanalysts.
So what were they doing exactly?
Each hut at Bletchley was tasked with the mission of attacking and deciphering the Enigma code employed by one of the German military forces. Hut 8 worked on breaking the Navy Enigma.
German military forces employed electromechanical “Enigma” machines, commercialised as early as 1919, to encrypt their messages. These machines looked like typewriters with a scrambler composed of (initially) three rotors, which would change the output of each typed letter in a complex manner, depending on the — daily changing — core (starting) positioning of the rotors. On top of this, the military Enigma machines employed by Germans had an additional security feature: a plugboard that interchanged letters in pairs at the source.
How to tackle this problem?
Clearly, trying to infer the daily settings of Enigma machines could not be done manually. Cryptanalysts used bombe machines, designed to test multiple hypotheses, i.e. try multiple rotor setups simultaneously and automate logical deductions.
In 1941, Hut 8 started employing a new cryptanalyst method developed by Turing, which became known as Banburismus (it used punch cards with representations of messages under attack printed in Banbury). This method utilized sequential conditional probability to infer weighted correlations and determine rotor settings to be tested on the Bombes, which were in short supply, making the process more time-efficient. More messages could be attacked now.
Joan was the sole woman and one of the best Banburists in the section.
One of Joan’s most important contributions to the project accelerated the solution of Naval Enigma Offizier signals, often extremely difficult to break, due to the use of a second set of plugboard settings. Joan also worked on speeding up other procedures (later formalized in the Yoxallismus).
Sadly the full extent of her contributions and accomplishments remains unknown (= confidential) due to the restraints of the Official Secrets Act and, at times, has been overshadowed by her relationship with Alan Turing, which we purposely did not cover in this article.
In any circumstance, her work on Naval Enigma helped shorten the war and saved many lives on both sides. Because of this, she was appointed as a Member of the Order of the British Empire (MBE) in 1946.
After the war
After the war, Joan worked for GCHQ (Government Communications headquarters), where she met Lieutenant-Colonel John K.R. Murray, who became her husband (1952). He had published some work on 16–17th Century’s Scottish coinage and Joan, intrigued by this, developed a numismatic interest of her own. Indeed, her research established the sequence of coins in circulation in Scotland at the time of James III and IV and in 1986 she was awarded Sanford Saltus Gold Medal by the British Numismatic Society for this scholarly contribution.
Little else is known about Joan’s personal interests as she was a very private person.
She died on 4 September 1996 at her home in Oxford.
Joan’s story has been portrayed in the movie “The imitation game”, where she was portrayed by Keira Knightley, who managed to show how she succeeded in her field despite working at a time in which “intelligence wasn’t really appreciated in women”.
TIMELINE
1917 — Born in West Norwood
1939 — Double first degree in mathematics (Cambridge University)
1940 — Recruited at the Government Code and Cypher School (GCCS) at Bletchley Park and join the codebreakers.
1946 — Appointed as a Member of the Order of the British Empire (MBE).
1952 — Marries Lieutenant-Colonel John K.R. Murray.
1986 — Awarded the Sanford Saltus Gold Medal by the British Numismatic Society.
1996 — Dies at her home in Oxford.
REFs / If you want to know more:
About the author and artist
DR. ELEONORA ADAMI
Content editor and contributing artist
Women in Science, Sci-Illustrate Stories
Eleonora is a proud descendant of ancient Romans. Besides that, she is currently a postdoctoral research fellow at Duke-NUS in Singapore, working in the cardiovascular and metabolic diseases area. She has a biotechnology (BSc) and functional genomics (MSc) background, and has obtained her PhD in molecular biology and genetics in Germany before going to the far east.
Eleonora thinks of herself as a carrier pigeon, always on the go, trying to find new adventures and challenges. Ok, maybe pigeons are not very adventurous, but they were once useful to deliver important messages. One of the messages she likes to bring across is that we need more art in scientific practices. Creative thinking benefits both disciplines.
A passion for illustration has always accompanied her and percolates in her scientific work. She started the collaboration with the Sci-Illustrate team after attending their course on scientific illustration.
About this series:
Not enough can be said about the amazing Women in Science who did and continue to do their part in moving the world forward.
Every month, through the artwork & words of the Sci-Illustrate team, we will bring to you profiles of women who touched our hearts (and brains) with their scientific works, and of many more who currently hold the flag high in their own fields!
-Dr. Radhika Patnala, Series Director
