Case Study

I have always been fascinated by cryptograms and secret codes. When I work on tough cryptograms, I usually create computer programs to assist me with some of the housekeeping work (counting letter frequencies, for example). While reading the classic book Cryptanalysis by Helen Fouché Gaines, I came upon an interesting cipher that screamed for computer assistance.

A grille cipher is a cipher in which you take a piece of metal or cardboard and punch holes in various sections. This piece of metal or cardboard is called the grille. You start writing your message in the punched out holes and when you run out of holes, you rotate the piece of metal 90°, but still over the same section of paper. You must take some care in deciding where to ...

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