The Playfair Cipher with Key DEATH

Playfair is a digraph cipher invented by Charles Wheatstone in 1854 and championed by Lord Playfair. You write the keyword's unique letters into a 5x5 grid (combining I and J), then fill the rest of the alphabet around it. Encrypted pairs of letters are decoded by their geometric relationship in the grid: same row, take the letters to the left; same column, take the letters above; rectangle, swap diagonals. Confederate intelligence used Playfair extensively during the Civil War, which is the reason Booth would have learned it. The keyword DEATH gives us a grid that decodes the digraphs to "Laboulaye Lady." Édouard de Laboulaye is the French jurist whose 1865 dinner-party suggestion became, twenty-one years later, the Statue of Liberty. There are several Laboulaye Ladies in the world. Three small replicas of the Statue stand in Paris.