Re: An interesting Hill cipher problem


"dave" <davidsnow6767@xxxxxxxxxxx> wrote in message
news:23969718.1141925856760.JavaMail.jakarta@xxxxxxxxxxxxxxxxxxxxxxxxx
This is a Hill Cipher implementation with 0=space, 1=a, 2=b, ... We have a
message p that is encoded as c=pK where K is a 2x2 matrix with integer
entries from 0 to 26 and both c and p are 1x2 vectors. The entries of c
are reduced modulo 27. So p=cK^-1 where K^-1 is the inverse, modulo 27, of
the matrix K. So I've found that the 2 most common vectors in the coded
message are UJ and HF (which correspond to [21 10] and [8 6] respectively)
and that these correspond to the uncoded message through parts of the word
"the" and spaces before and after the word (ie. "space T"=[0 20], "TH"=[20
8], "HE"=[8 5], and "E space"=[5 0]). I'm not sure which these two
specifically correspond to but I've tried all combinations in solving for
K and can't seem to get a K that has all integer entries. Can anyone find
this K or its inverse?

I can't help you with an answer, but I can help you with newsgroup posting.

If you change the subject to "Hill cipher problem", you are far more likely
to have your post actually read by somebody who can answer your question. As
an added benefit, those of us who know nothing about Hill ciphers (and I
suspect there are many) won't waste our time reading your question.


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