Re: Q: Attacking multi-symbol substition?

From: Jim Gillogly (jim_at_acm.org)
Date: 05/30/03 

Date: 30 May 2003 10:48:31 -0700

benranck@mail.com (benjaminR) wrote in message news:<7e2a616e.0305292054.1380f4f8@posting.google.com>...
> I've got a cipher message which
> I'm fairly sure is a multi-symbol substitution cipher,
> there are no more than 4 of any one symbol and I've been given
> a hint that there are 4 different symbols for e.
> I've managed to find one
> repeated trigram which I'm fairly sure is 'the'
> but other then that I'm stuck, that only gives me
> 12 letters out of 158. Which just isn't enough
> to work with. Any tips or ideas on attacking this kind of cipher?

This general kind of cipher is called "homophonic", but if you google it,
you'll see a lot of a specific kind of cipher with that name using 2-digit
groups. To make more progress, try identifying some of your variant symbols
by looking for "almost-matches". That is, if you have a 10-symbol string
that nearly matches another 10-symbol string except for the 2nd and 7th
places, try treating the symbols in those two places as homophones and
repeating the process, seeing if more strings "almost match". In this way,
if you have enough text, you may be able to reduce it to simple substitution.

           Jim Gillogly

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