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the playfair cipher is a manual symmetric encryption techniue and was the first digraph substitution cipher  the scheme was invented in eighteen hundred fiftyfour by charles wheatstone  but bears the name of lord playfair who promoted the use of the cipher  the playfair cipher uses a five by five table containing each letter in the english alphabet exactly once  except  which is missing   the table constitutes the encryption key  to more easily remember the table  it is typically generated from a key phrase  first fill in the spaces in an empty table with the letters of the key phrase  dropping spaces and duplicate letters   then fill the remaining spaces with the rest of the letters of the alphabet in order  the key phrase is written in the top rows of the table  from left to right  for instance  if the key phrase is playfair example  the encryption key becomes
