TheCodeBreakers
latter form. Playfair thus constructed a square based on PALMERS-TON,
with the remaining letters of the alphabet following, to illustrate the
cipher at Granville's dinner:
PALME R S T O N B C D F G H IJ K Q U V W X Y Z
To encipher, the plaintext is divided into pairs. Double letters
occurring together in a pair must be separated with an x, so that balloon
would be enciphered as ba Ix lo on; i and / are regarded as identical, so
that adjacent will be enciphered as if it were adjiacent. Now the letters of
each pair may stand in only three relationships to one another within the
square: the two may appear in the same row, in the same column, or in
neither. Letters that fall in the
*An earlier author's digraphic table used not letters but signs.
same row are each replaced by the letter to its right. Thus, am = LE, hi
= IK, os = NT. Each row is considered cyclical, so that the letter to the
right of the last letter in a row is the first letter at the left of that row.
annaabi.ee 
