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Double Transposition Cipher Solution
Back to Double Transposition Hint
Normally the keys would be numbered like this:
11 1 1 1
81520194673 327811504692
MAHATUNDILA CULLATINDILA
However, Agent Madeleine numbered the duplicate A's and L's from right to left
instead of from left to right, so it would be the equivalent of replacing the keys
with MCHBTUNDILA and CUMLBTJNDIKA, then doing the normal double transposition.
Taking columns in the wrong order was such a common mistake that it had a name -
"hatting." The plaintext of the message is:
FOUND SHELTER WITH CHILDHOOD FRIEND IN SURESNES STOP
TRANSMITTING FROM HOME OF VAUDEVIRE STOP
WILL MEET WITH BERTRAND TO DISCUSS SCHEDULES
AND COORDINATE TRANSMISSIONS FROM SURVIVING AGENTS STOP
PLEASE SUPPLY DEscriptION OF BERTRAND END MESSAGE
While the plaintext appears almost banal, in fact agents in occupied
France were in continual grave danger, and a botched communication or one that
did not get a useful response in time could be fatal.
Agent Madeleine was Noor Inayat Khan, an author and FANY. (A FANY was typically a
young woman in the Field Auxiliary Nursing Yeomanry, the work force tapped when someone
needed some bright young people who were unsuitable for combat positions.) Madeleine
survived longer than the rest of her cell, and for a time was the only free British-controlled
wireless operator in Paris. Although contacting previous acquaintances was against
regulations, she had little choice, and some of her friends did in fact put her up
in Suresnes. Her duress code was to use a double transposition key with precisely
18 letters, so we know this message was not sent under duress. Her meeting with
Bertrand led to her capture: The real Bertrand had already been caught, and she
met a phony Bertrand and unwittingly gave away some useful information before
she was taken into custody. The Nazis forced her to continue sending for a time,
and the first message she sent had a key of precisely 18 letters. I invented
this message to try to get her a warning in time and change history. Ah, well.
She was an excellent coder and probably would not have made the errors shown here;
however, many operators, such as the Norsk Hydro informant Einar Skinnarland, made
horrendous blunders frequently, and both Leo Marks, head of the coding section for
the Special Operations Executive, and the Coders of Grendon, one of a number of
code sending and receiving crews trained by Marks, tore their hair out over them.
For more background see Between Silk and Cyanide: A Codemaker's War 1941-1945
by Leo Marks (Free Press, 1999), and Set Europe Ablaze by E. H. Cookridge (Thomas Y. Crowell, 1967).
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