Wednesday, 9 January 2019

Hiding messages

For as long as there's been chess, there has been suggestions that chess games can be used to send coded messages. Both correspondence chess, and telegraph chess, have run into problems, when state security officials have misunderstood what they were looking at.
However, I have come across an article (from October 2018) where James Stanley has proposed a scheme of using chess moves to encode messages. His method involves turning the letters in numbers, and then uses part of the number to generate legal moves. This is done by generating a list of moves in a position, sorting them in order and matching the number to the move index (eg If Nf3 was the 12th move in the list of moves, this would represent the number 12).
There is one flaw this system (as the author himself recognises) and that is the ordering of the moves. He sorts them in canonical order (eg a3 comes before b4 etc), and while this means both sender and receiver both agree on an order, it makes the games themselves rather silly. Any chess literate security agent who saw such a game would realise pretty quickly that this wasn't a proper game of chess. One possible improvement is to use an agreed chess engine (and search depth) to order the moves, but even then, if you need to use the 15th best move, it is going to be a pretty horrible one!

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