[Blog Post] Spatial Spread And Conditional Character Entropy Reduction

[pfeaster]

Here is a recent article, You are not allowed to view links. Register or Login to view., Arroyo et al. (2020) that includes a lot of interesting adaptions of the Polybius square.  

Thanks much for sharing!

Just in the interests of completeness, I'd like to throw my own You are not allowed to view links. Register or Login to view. cipher into the mix as yet another adaptation of the Polybius Square (and one I came up with specifically as an experiment in trying to mimic Voynichese -- I think it's been brought up here in the past, but before I joined the forum).  It uses the Polybius Square as a kind of gameboard, and instead of enciphering characters consistently by their coordinates, it enciphers the paths taken by a token around the board to get from one point to another.  By repeating the same "moves" on a similar board, a reader can reconstruct the plaintext.

This approach has definite limitations when it comes to imitating Voynichese (which are more obvious to me now than they were then), but it was a fun experiment -- and, like some other examples given in that article, it *does* provide security against frequency analysis attacks.