Playfair Cipher
Encrypt or decrypt using the Playfair pair-substitution cipher.
The grid drops the letter J and merges it into I, which is standard for Playfair. Identical letters in a pair get split with an X, and odd length plaintext is padded with an X. Spaces and punctuation are stripped before encryption.
About
Playfair encrypts pairs of letters using a 5x5 grid built from a keyword. Used by the British Army in WWI. More secure than Caesar but breakable with frequency analysis on bigrams.
How to use
- Enter a keyword.
- Enter your text.
- Toggle encrypt or decrypt.
FAQ
How does the 5x5 grid work?+
The keyword fills the grid first (no repeats), then the rest of the alphabet. I and J share a cell. Encryption rules depend on whether pair letters are in the same row, column, or rectangle.
Is Playfair secure?+
No. Hand-cracked in WWI. Bigram frequency analysis breaks it within a few hundred characters. Useful for puzzles and history, not real secrets.