🚀 go-pugleaf

In article <1992Nov18.194435.18141@cas.org>, jac54@cas.org () writes:
|> >To encrypt:
|> >    0) compose the message
|> >    1) add (to both the front, and the back) additional characters,
|> >       chosen to produce a flat histogram.  Pseudo-randomize, as needed.
|> >       Perhaps also pad to a standard size block?
|> >       Perhaps randomize the positioning of the message within the block?
|> >       Perhaps break the original message into bite-sized pieces and
|> >       include additional material between bites as well as at the
|> >       beginning and end?
|> >    2) apply the character transposition cipher.
|> 
|> 	Read the article the"Two Soviet Spy Ciphers" by David Kahn in
|> 	"Kahn on Codes".  The system used by Hayhanen did several of
|> 	these things and, if I remember correctly, everything was
|> 	susbtituted first. 


If my memory serves me -  Hayhanen system didn't have a SINGLE null.
Basically it's monoalphabetic substitution followed by two irregular
columnar transpositions. What gives it strength are:
	1) Substitution's done via straddling checkerboard.
	2) All the keys are generated using pseudo-random sequence,
	   which in turn differs from message to message (and it's
	   based on a truly random number which is added to the
	   final ciphertext in prearranged place).
	3) Second transposition has D-areas, which mess things a lot
	   for a cryptanalist.


|> 	Despite all this, I think
|> 	the transposition would fall to multiple anagramming fairly
|> 	quickly.  Somebody very patiently explained to me that
|> 	transpositions are considered very weak these days.

It really depends! (:-) [Unless you meant transposition alone.]
Substitution+Transposition is the strongest combination! (:-)


|> 	Incidentally, the Soviets seem to have put a lot of effort
|> 	into putting field-expedient ciphers together so that they
|> 	wouldn't forever be delivering one-time pads to their
|> 	people.

I would assume one-time pads are still in use both here and there.
But it is convenient to save one-time pads for the top guys, while
lesser folks can get almost-unbreakable mnemonic system!   Neat...
But nothing can really beat one-time pad! (:-)
-- 
Regards,
Uri.		uri@watson.ibm.com
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