Bifid Cipher

Fractionating cipher combining a Polybius square with transposition.

The Bifid cipher combines the Polybius square with transposition, and uses fractionation to achieve diffusion. Keys for the Bifid cipher consist of a 25-letter key square. The key square can be generated using a keyword, with the remaining spots filled by the rest of the alphabet in order. Usually the letter J is merged with I, but you can customize that in the Alphabet Options.

You can choose a period grouping to split the text into blocks, or leave it blank to use the full text length.

Plaintext

Alphabet

Use the "Alphabet Options" to customize your alphabet. Default letter swap is J for I.

This cipher only has 25 characters, so one character must be switched.

Switch

Into

Keyword or phrase

Use last instance of keyword letters Reverse keyword Put keyword on right side Reverse alphabet portion Randomize alphabet Reverse final result

Period Grouping

Ciphertext

Bifid Cipher

Polybius Square