Porta Cipher

The Porta Cipher is a polyalphabetic substitution cipher invented by Giovanni Battista della Porta. Where the Vigenère cipher is a polyalphabetic cipher with 26 alphabets, the Porta is basically the same except it only uses 13 alphabets. The 13 cipher alphabets it uses are reciprocal, so enciphering is the same as deciphering.

The algorithm (and tableau) used here is the same as that used by the American Cryptogram Association.



The Porta Cipher uses the following tableau to encipher the plaintext: