Enter the key square below and choose whether a letter needs to be substituted or choose a letter to be omitted, since the key square can only contain 25 letters. By default J is replaced by I. Now select how to deal with double letters. Finally select encryption or decryption and enter the text to convert it.

The Playfair cipher is a manual symmetric encryption technique and was the first literal digraph substitution cipher. The scheme was invented in 1854 by Charles Wheatstone, but bears the name of Lord Playfair who promoted the use of the cipher.