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Four Square Cipher
Digraph substitution cipher using four 5 by 5 squares.
The Four-square cipher encrypts pairs of letters, making frequency analysis harder than with simple substitution ciphers. It uses four 5 by 5 matrices: the upper-left and lower-right are plaintext squares, and the upper-right and lower-left are keyed ciphertext squares.
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This cipher only has 25 characters, so one character must be switched.
This cipher only has 25 characters, so one character must be switched.
Transform
Find & Replace
Group
Every
chars