Sir Peter Baldwin obituary - Senior civil servant and wartime code-breaker

Wednesday 9 June 2010

Sir Peter Baldwin obituary
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Senior civil servant and wartime code-breaker

Terence Bendixson

As a young man, Peter Baldwin, who has died aged 87, played an important, 
if little-known, role in breaking codes used by the Japanese government 
during the second world war. He devoted the last decades of his life to 
numerous disability charities. In the intervening years, he achieved 
distinction as a civil servant, becoming permanent secretary at the 
Department of Transport.

From 1940 onwards, Baldwin was at work as a decoder in "Rm 25, Mil Sec, 
Hut 4, Block F" at Bletchley Park, in Buckinghamshire. To keep abreast of 
the activities of the European allies, Tokyo's military attaches were sent 
to Berlin, Rome, Lisbon, Vienna, Stockholm and, after the occupation of 
Paris, Vichy. All were equipped with a cipher system, the Japanese 
Military Attache ( JMA ) code, thought to be impenetrable. The code was 
based on a book, or "key", containing pages of lines and columns of 
randomly chosen letters, and a second random alphabetical mesh known to 
cryptographers as a Vigenère square. In Hut 4, this was called the 
"square".

For diplomats using this cipher system to send intelligence back to Tokyo, 
it was a tedious business. The attache had first to turn his kanji script 
into alphabetic "words", then use the keybook to convert the resulting 
sequence of letters into a second sequence and then, using the "square", 
transpose those letters yet again. This put the message in the equivalent 
of one locked box inside another. A cryptanalyst seeking to read it needed 
to find the key to both.

So secure was the JMA code that the two boxes were inside a third. This
was a three-letter sequence, itself encoded, and buried in every Morse
transmission. This revealed on which page and line of the key the coded
messages began. Attaches were told to start every message at a different
place in the key but, happily for Baldwin and his colleagues, Tokyo's man
at Vichy was lazy. He inserted the same short sequence of letters in the
same place in his messages for several months. This repetition, once found
by the cryptanalysts, gave them an opening. Using a mix of logic and
imagination, they began to break open the attaches' code. Further progress
was made in 1943, when Baldwin had the idea that all messages might
include a second indicator telling where in the key they ended. Baldwin
later said that the JMA team at Bletchley "provided unbroken access" to
the code "through the war years until the exit of the attaches as the fall
of Hitler became imminent"..../snip/

- Peter Robert Baldwin, civil servant,
  born 10 November 1922; died 9 May 2010


http://www.guardian.co.uk/politics/2010/jun/08/sir-peter-baldwin-obituary

http://static.guim.co.uk/sys-images/Guardian/Pix/pictures/2010/6/8/1276015712117/baldwin-006.jpg

http://www.timesonline.co.uk/tol/comment/obituaries/article7135290.ece

http://www.timesonline.co.uk/multimedia/archive/00720/baldwin_1C_585x350_720510a.jpg