Porta Cipher uses a polyalphabetic substitution cipher. It uses uses 13 alphabets, and which are reciprocal, thus enciphering becomes the same as deciphering.
Porta cipher |
Example
We take two characters at a time and use the following mapping:
Keys| a b c d e f g h i j k l m n o p q r s t u v w x y z --------------------------------------------------------- A,B | n o p q r s t u v w x y z a b c d e f g h i j k l m C,D | o p q r s t u v w x y z n m a b c d e f g h i j k l E,F | p q r s t u v w x y z n o l m a b c d e f g h i j k G,H | q r s t u v w x y z n o p k l m a b c d e f g h i j I,J | r s t u v w x y z n o p q j k l m a b c d e f g h i K,L | s t u v w x y z n o p q r i j k l m a b c d e f g h M,N | t u v w x y z n o p q r s h i j k l m a b c d e f g O,P | u v w x y z n o p q r s t g h i j k l m a b c d e f Q,R | v w x y z n o p q r s t u f g h i j k l m a b c d e S,T | w x y z n o p q r s t u v e f g h i j k l m a b c d U,V | x y z n o p q r s t u v w d e f g h i j k l m a b c W,X | y z n o p q r s t u v w x c d e f g h i j k l m a b Y,Z | z n o p q r s t u v w x y b c d e f g h i j k l m a