The encryption process using a Polybius Square is fairly straightforward. First we have to generate the Mixed Square, using a keyword as above (or another rule such as reversing the alphabet, or shifting the alphabet). Once the Mixed Square is generated, we replace each letter with the "coordinates" of the letter within the grid, reading across first and then down.
As an example, we shall encrypt the plaintext "nice and simple" with the keyword example.
First we make the Mixed Square using the keyword. We start by filling in the squares in the grid with the letters of the keyword, ignoring repetitions, and then continue with the rest of the alphabet.
The Mixed Square using keyword example
With the Square complete, we simply find each plaintext letter in the grid, and replace it with its coordinates. So "n" becomes "53", "i" becomes "33", "c" becomes "32" and so on. Continuing like this we get the ciphertext "53333211 315342 443341511211".
As an example, we shall encrypt the plaintext "nice and simple" with the keyword example.
First we make the Mixed Square using the keyword. We start by filling in the squares in the grid with the letters of the keyword, ignoring repetitions, and then continue with the rest of the alphabet.
The Mixed Square using keyword example
With the Square complete, we simply find each plaintext letter in the grid, and replace it with its coordinates. So "n" becomes "53", "i" becomes "33", "c" becomes "32" and so on. Continuing like this we get the ciphertext "53333211 315342 443341511211".