Polybius Square Cipher
Encode letters as row/column coordinates in a 5×5 grid.
Encoded
Polybius Square (I and J share position 24)
| 1 | 2 | 3 | 4 | 5 | |
|---|---|---|---|---|---|
| 1 | A | B | C | D | E |
| 2 | F | G | H | I | K |
| 3 | L | M | N | O | P |
| 4 | Q | R | S | T | U |
| 5 | V | W | X | Y | Z |
How the Polybius Square Works
The Polybius square is a 5×5 grid containing the alphabet (I and J share one cell). Each letter is encoded as its row number followed by its column number — so A = 11, B = 12, Z = 55. To decode, split the digits into pairs and look up the row/column. It is one of the building blocks of more complex ciphers like the ADFGVX cipher used in WWI.
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