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Bifid Cipher

Mix Polybius square coordinates in fixed-size blocks to create a fractionating classical cipher.

Learn how the Bifid cipher works

Input

Output

Using This Tool: Guide & Notes Show guide

The Bifid cipher combines Polybius coordinates with fractionation, mixing row and column numbers inside fixed periods.

How to use it

  • Set the keyword or square used for the Polybius grid.
  • Choose the period length.
  • Paste plaintext or ciphertext into the input box.
  • Use the coordinate preview to see how rows and columns are split and recombined.

Options and settings

  • Keyword changes the Polybius square and therefore every coordinate.
  • Period controls how many letters are mixed together before output is produced.
  • I/J handling affects how the 25-cell square represents the alphabet.
  • Grouping formats the final ciphertext for easier reading.

Notes

  • A longer period mixes letters more widely, but this is still a historical cipher.
  • Wrong period or square settings prevent clean decryption.
See all tools
ADFGX Cipher Use a keyed ADFGX square followed by keyed columnar transposition. ADFGVX Cipher Use a keyed ADFGVX square with letters and digits, then apply keyed columnar transposition. Nihilist Cipher Encrypt or decrypt numeric Nihilist ciphertext with a keyed Polybius square and repeated additive key. Vigenère Cipher Polyalphabetic substitution cipher using a repeating key.
Related Article

Bifid Cipher: When Coordinates Get Split Apart

How the Polybius square became a fractionating cipher that mixed letters before turning them back into text.

Read the article
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A note from the team

We build these tools because we love cryptography, encoding, and making difficult ideas easier to explore. If they've helped you, even a small coffee means the world to the project. Thank you!

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