[Cryptography] Code Breakers by Craig Collie

[Bill Frantz]

I found an interesting book in a Sydney, Australia airport book stall:

Code Breakers
Inside the shadow world of signals intelligence in Australia's 
two Bletchley Parks
Craig Collie
First published in 2017 by:
Allen & Unwin
83 Alexander Street
Crows Nest, NSW 2065
Australia
<www.allenandunwin.com>
ISBN 978 1 74331 210 0

This book describes the signals intelligence efforts in 
Australia during WWII. It goes into detail about the politics, 
personalities, code breaking, and traffic analysis used in some 
of the epic battles in the south Pacific. It describes the early 
use of IBM tabulating equipment in code breaking. It gives 
enough detail about the structure of the Japanese codes so the 
reader can appreciate the effort needed to break them and 
re-break them after they were changed.

A brief description of the typical code structure: First the 
messages was converted to numbers using a code book which took 
words or phrases as input. Then "additive tables" were used like 
a one time pad to scramble the output of the code book for 
transmission. Since the additive tables were reused many times, 
there were obvious security issues, although these issues don't 
seem to have been the major way the codes were actually broken.

Traffic analysis based on the strength and direction of radio 
signals allowed prediction of air attacks without being able to 
read the messages, although since the airplane codes were 
designed for easy use in the air, they were relatively easy to break.

The book is also a fun read. Recommended.


Cheers - Bill

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