Sacco-Notebook-bar

Italian cryptologist Luigi Sacco left behind a text encrypted with a Fleissner grille. Paolo Bonavoglia and Bart Wenmeckers, both readers of this blog, solved it.

Fleissner-Grille-bar

The Fleissner grille is one of the most popular encryption tools. In spite of its popularity, surprisingly little has been published about deciphering a Fleissner grille. I wonder if a reader can break the Fleissner challenge I am going to present today.