Enter JIG in the Polybius tool. I and J share a cell in its 5 × 5 square, so the prepared message becomes IIG. We will find each coordinate, then decode the result to see why the original J cannot be recovered from the numbers alone.
1. Locate the prepared letters
| Row / column | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|
| 1 | A | B | C | D | E |
| 2 | F | G | H | I / J | K |
| 3 | L | M | N | O | P |
| 4 | Q | R | S | T | U |
| 5 | V | W | X | Y | Z |
2. Read row, then column
| Original letter | Prepared letter | Row | Column | Token |
|---|---|---|---|---|
| J | I | 2 | 4 | 24 |
| I | I | 2 | 4 | 24 |
| G | G | 2 | 2 | 22 |
JIG with I and J sharing a cell
JIGI/J merged; prepared IIG; row then column24 24 22The first two numbers match because both prepared letters use the same cell. Read 24 as row 2, column 4. Reversing the order would point to row 4, column 2, which contains R.
3. Compare with prepared input
Decode 24 24 22 with the same square to get IIG. That is the correct prepared text, but it does not reveal which of the first two letters might originally have been J. Keep the original spelling if that distinction matters to your puzzle.
4. Spot a coordinate outside the square
Try decoding 26. There is no column 6 in this square, so the tool flags the token. Check the intended coordinate instead of wrapping it around or guessing a letter.
Your turn
Encode JOIN and write both the prepared form and the ciphertext.