Polybius Square — Coordinate Substitution Cipher, one of the earliest substitution ciphers
○ Using default order
📊 6×6 Square
| 1 | 2 | 3 | 4 | 5 | 6 | |
|---|---|---|---|---|---|---|
| 1 | 0 | 1 | 2 | 3 | 4 | 5 |
| 2 | 6 | 7 | 8 | 9 | A | B |
| 3 | C | D | E | F | G | H |
| 4 | I | J | K | L | M | N |
| 5 | O | P | Q | R | S | T |
| 6 | U | V | W | X | Y | Z |
Lookup: row first, column second → (row, column)