Matrix Ciphers - Introduction to Cryptography with Java Applets - page 157

The plaintext “BLOW ME DOWN,” padded with X's:
1 22 3 13
p = 11 12 14 23
14 4 22 23
Do the first substitution:
4 2 17 20
20 24 13 3
1 8 18 16
Do the transposition:
17 4 20 2
13 20 3 24
18 1 16 8
Do the second substitution.
The final ciphertext is “IAH OVV DLX WQQ”.
8 14 3 22
0 21 11 16
7 21 23 16
Begin decryption—reverse second substitution:
17 4 20 2
13 20 3 24
18 1 16 8
Reverse the transposition:
4 2 17 20
20 24 13 3
1 8 18 16
Now reverse the first substitution, and the recovered plaintext is “BLO
WME DOW NXX.”
1 22 3 13
11 12 14 23
14 4 22 23