DIGRAPH SUBSTITUTION
Playfair Cipher
A cipher that encrypts pairs of letters using a 5×5 key square.
Key Square
M O N A R
C H Y B D
E F G I K
L P Q S T
U V W X Z
C H Y B D
E F G I K
L P Q S T
U V W X Z
Important Concept
Playfair works on pairs of letters rather than individual characters.