Portax Tutorial


The Portax cipher is a periodic, digraph based cipher similar to the Slidefair. Like the Slidefair, it is based on one of the classic periodic ciphers (The Porta in place of the Vigenère, Variant or Beaufort used by Slidefair). The major difference between the two ciphers is the method of choosing the digraphs the cipher is applied too. In Slidefair the digraphs are taken sequentially from the plain text. In Portax, the plain text is laid out in pairs of rows of period length and the the digraphs are formed from the vertical columns. Continue reading Portax Tutorial

Foursquare Tutorial


The Foursquare cipher is a digraphic substitution cipher similar to the Playfair. Unlike the Playfair cipher, which is based on a single Polybius square, Foursquare uses 4 Polybius squares arranged into a single large square. The four squares are labeled from 1 to 4 starting in the upper left and proceeding clockwise. Squares 1 and 3 contain unkeyed plaintext alphabets placed in the normal order. Squares 2 and 4 are keyed ciphertext alphabets and may be placed in the squares in any of the usual ways. Continue reading Foursquare Tutorial

Playfair Tutorial


The Playfair cipher is a digraphic substitution cipher based on a 5 x 5 Polybius square formed with a keyword (N.B., I/J are considered equivalent). The plain text is broken up into two letter combinations (digraphs). Double letters are not permitted and must be separated by inserting a null (Usually an ‘X’). If a single letter is left at the end of the plain text, a null is also inserted there to complete the digraph. Continue reading Playfair Tutorial