Polybius square
Letters in a 5x5 grid, each written as a pair of numbers: row and column. You can tap it, flash it or clap it.
Try it
27 characters
Result · Polybius square
43 15 13 42 15 44 / 32 15 43 43 11 22 15 / 21 34 42 / 44 23 15 / 13 31 45 12
How it works
- 1Draw a 5x5 grid and write the alphabet into it row by row. Number the rows and columns 1 to 5. There are 26 letters, so I and J share one square.
- 2Find each letter of your message in the grid and write the row number first, then the column number. B is row 1, column 2, so it is 12.
- 3Write the numbers in pairs. Words are separated by a slash; digits and punctuation are left out.
- 4To decode, split each pair into row and column and look the letter up. Want it harder? Add a keyword - the letters in the grid get rearranged.
Example
Hello world
Did you know
The grid is named after the Greek historian Polybius, who lived in the 2nd century BC. He described using it to signal with torches: the number of torches held in the left hand gave the row and the number in the right hand gave the column. The same idea is still used in games, scout puzzles and for tapping messages on a wall or a pipe.
Try to decode
This message is encrypted with Polybius square using the default settings:
32 15 15 44 / 11 44 / 44 23 15 / 12 42 24 14 22 15
Hint
The grid is ABCDE / FGHIK / LMNOP / QRSTU / VWXYZ. The first number is the row, the second the column: 43 is S.
Show solution
MEET AT THE BRIDGE
More ciphers in this category
- Caesar cipherEvery letter moves a fixed number of places along the alphabet. The most famous cipher in the world and a perfect first step.
- Vigenère cipherA Caesar cipher with a password: each letter shifts by a different amount set by the keyword. Much tougher than plain shifting.
- AtbashThe alphabet flipped like a mirror: A becomes Z, B becomes Y. No key, no settings, and decoding is the same as encoding.
- ROT13A Caesar cipher with a shift of 13: the same steps encode and decode. No settings, just one click.