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Messages Behind Masks
Girolamo Cardano invented the Cardano Grille, a form of hidden writing called "steganography." The grille was a mask with word-sized cutouts. The sender laid the grille on a piece of paper, wrote the message in the cutouts, then removed the grille and filled the remaining spaces with an innocent-sounding message. The recipient placed an identical grille on the letter to revewal the secret message. |