1
Poly
Poly


Graphic Substitution:
Graphic Substitution:
Playfair
Playfair
(1854)
(1854)
•
Encrypts pairs of letters in each step
•
Build a 5 x 5 table of the letters using the key and
other letters
•
Example: Key =
”MONARCHY”
M
O
N
A
R
C
H
Y
B
D
E
F
G
I/J K
L
P
Q
S
T
U
V
W
X
Z
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2
Playfair
Playfair
Cipher
Cipher
Rules for substituting a pair of plaintext letters:
•
Repeated letters in the plaintext are separated with a filler
letter (such as X)
•
Two plaintext letters that fall in the same row of the 5 x 5
table, are replaced by two letters that reside to their
immediate right in the table (with circular wraparound)
•
Two plaintext letters that fall in the same column of the 5 x 5
table, are replaced by two letters that reside their immediate
beneath in the table (with circular wraparound)
•
Otherwise, each plaintext letter (of a pair) is replaced by the
letter that lies in its own row and the column occupied by the
other plaintext letter (of the pair)