Cryptography Reference
In-Depth Information
Converted to numbers (using Table 7.1) the message is
18 2
14 14
1 24
3 14
14 22
7 4
17 4
0 17
4 24
14 20.
C
AP
B
When we apply the matrix transformation
+
(mod 26), we get the results
shown in Table 7.2.
Now, we regroup the ciphertext into blocks of length 5.
25 0 1 8 2
2 24 16 7 24
4 12 2 0 8
23 17 14 25 20
. (See Table 7.3.)
Finally, we regroup the ciphertext into blocks of length 2, and reapply the first matrix
transformation. (See Table 7.4.)
The final ciphertext is
We apply the transposition cipher
C
=
TC
CT PK ZH HG HA VK PG YV SE QU.
What makes ciphers like this so difficult for anyone doing frequency analysis is that the
blocks are split up by the enciphering transformation. You should verify that the plaintext
is regained by applying the inverse matrix transformation (at the beginning and the end)
using
17
5
A
=
18
23
P
18 2
14 14
1 24
3 14
14 22
7 4
17 4
0 17
4 24
14 20
C
25 0
1 8
2 2
24 16
7 24
4 12
2 0
8 23
17 14
25 20
TABLE 7.2
C
25 0 1 8 2
2 24 16 7 24
4 12 2 0 8
23 17 14 25 20
C
8 25 2 0 1
7 2 24 24 16
0 4 8 12 2
25 23 20 17 14
TABLE 7.3
C
8 25
2 0
1 7
2 24
24 16
0 4
8 12
2 25
23 20
17 14
C
2 19
15 10
25 7
7 6
7 0
21 10
15 6
24 21
18 4
16 20
TABLE 7.4
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