Playfair Cipher
Encrypt or decrypt text with the classic Playfair cipher, built from a keyword-generated 5×5 grid.
About this tool
A 16th-century pen-and-paper cipher, not real security — encrypts letter pairs (digraphs) rather than single letters, using the shared grid. I and J are treated as the same letter, and an "X" is inserted to split any repeated pair or odd final letter.