Summary: EXAMPLE 2. (Similar to example 1, but with a plaintext leading to a not-invertible
matrix.)
We know that the first four letters of the ciphertext starting with WKNCCHSSJH
deciphers to "give" and that a block code (mod 26) is being used. We try to find the NxN
deciphering matrix D starting with N=2, N=3, etc.
The information that WKNC deciphers to give leads to the matrix equation:
!
22 10
13 2
"
#
$
%
&
'D (
6 8
21 4
"
#
$

Source: Akhmedov, Azer - Department of Mathematics, University of California at Santa Barbara

Collections: Mathematics