Encrypt and decrypt with the Bifid cipher combining a Polybius square with coordinate fractionation. Bifid Cipher is a free online tool from the ToolsRift Text Encoding Tools collection. It runs entirely in your browser — nothing to install, no signup, and your data never leaves your device.
Each letter is converted to its row and column in a 5×5 Polybius square. All the row numbers are written out first, then all the column numbers; this combined sequence is re-paired into new coordinates and turned back into letters, spreading each letter's influence across the message.
Yes. A keyword rearranges the Polybius square (I and J share a cell). Leave the keyword blank to use the plain A–Z square. Both sides must use the same keyword to decode correctly.
Yes, for letters. Because fractionation is fully reversible, decoding with the same square returns the original text (J is read back as I, output uppercased).