Playfair code software

To generate the table, one would first fill in the spaces of the table with the letters of the keyword dropping any duplicate letters , then fill the remaining spaces with the rest of the letters of the alphabet in order to reduce the alphabet to fit you can either omit "Q" or replace "J" with "I".

In the example to the right, the keyword is "keyword". To encrypt a message, one would break the message into groups of 2 letters. If there is a dangling letter at the end, we add an X. For example. In this instance, you just slide the characters one position to the right, resulting in "MP". The same happens for "ON", resulting in "PO". By shifting one position right, we scroll around back to the left side and get A.

All non-letters are ignored and not encoded. The one letter that you select to share a square in the cipher is translated. Numbers, spaces, and punctuation are also skipped.

If you leave two letters together in a two-letter chunk, they will be encoded by moving down and right one square "LL" becomes "RR" where as traditional Playfair ciphers will automatically insert an X for you.

This particular cipher was used by the future U. President, John F. Kennedy, Sr. He sent a message about a boat going down. Encode double letters down and right one spot. The Playfair cipher was the first practical digraph substitution cipher. The scheme was invented in by Charles Wheatstone but was named after Lord Playfair who promoted the use of the cipher.

In playfair cipher unlike traditional cipher we encrypt a pair of alphabets digraphs instead of a single alphabet. This was because Playfair is reasonably fast to use and requires no special equipment. Each of the 25 alphabets must be unique and one letter of the alphabet usually J is omitted from the table as the table can hold only 25 alphabets.

If the plaintext contains J, then it is replaced by I. The initial alphabets in the key square are the unique alphabets of the key in the order in which they appear followed by the remaining letters of the alphabet in order. Algorithm to encrypt the plain text: The plaintext is split into pairs of two letters digraphs.

If there is an odd number of letters, a Z is added to the last letter. For example: PlainText : "instruments" After Split: 'in' 'st' 'ru' 'me' 'nt' 'sz' 1. Pair cannot be made with same letter. Break the letter in single and add a bogus letter to the previous letter.