Steganography & covert communications - Between Silk and Cyanide

[John Gilmore]

> generally, imagine you are a consultant to some nefarious 
> organization and think about what it would take to convince them that 
> the method you propose is safe, capable of being taught to their 
> covert agents, and tolerant of the inevitable slip ups in the field 
> (and remember their attitude toward warrantee disclaimers).

Along these lines I can't help but recommend reading one of the best
crypto books of the last few years:

	Between Silk and Cyanide
	Leo Marks, 1999

This wonderful, funny, serious, and readable book was written by the
chief cryptographer for the 'nefarious organization' in England which
ran covert agents all over Europe during WW2 -- the Special Operations
Executive.  He found upon arriving (as a teenager) that agents were
constantly dying in the field because of poor codes and poor
encryption and radio transmission practices.  Their bad systems had
been penetrated for years, and in some countries such as the
Netherlands, all of their agents had been killed or captured by the
Germans.  He shored up their poor systems until he could work around
the bureacracy to get them replaced.  He taught the receiving code
clerks in England how to decode even garbled messages, rather than
asking agents to re-send them.  (Re-sends of the same text gave the
enemy even more trivial ways to crack the codes.)  He trained each
outgoing agent in good coding practices, then watched heartbroken as
many were captured.  He independently reinvented one-time pads, and
had them printed on silk.  They could be sewn into the linings of
clothing for non-detection even during searches by the enemy, and so
that as each part was used, it could be cut off and burned to keep
previous messages secret (providing forward secrecy).

Leo Marks died almost a year ago, but fortunately he wrote down much
of the practical knowledge that came from making and breaking codes
for a covert organization working in a very hostile environment.  Here
is his AP obituary:

  http://surf.bookwire.com/news/authors/2001/01/22/wstm-/2440-1571-Britain-Obit-Marks..html

	John Gilmore



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