25 Mar '11 15:43>1 edit
Originally posted by Nowakowski64 bits? Nonsense. 8 ranks, 8 files. 3 bits each. 6 bits for a square. 6 more for the "to" square. The latter can be brough down to 5 bits because whatever piece is on the "from" square, it can move to 27 squares maximum (queen in the centre), but that's too much trouble for too little gain. So the total number of bits you need to encode is 12. Even if you stick to just the alphabet, that's three characters at most, with room for fudging left over. Seems to me that that leaves a lot of room for steganography as well as cryptography.
First, an important point here is that we know the total message length is 64. So any kind of block cypher can be used and salted - although this is not the route that we will be taking here…for simplicities sake.
In fact, it's even easier than that. All you need to do is give each rank a letter as well as each file. Doesn't have to be a-h, doesn't have to be distinct from a-h, may even partially and only partially overlap a-h.
Now, send a message containing normal text. Make sure that in the first word, the first letter from a-h indicates the starting file. Note that this doesn't have to be the first letter! If you want a piece on the H-file to move, the word "The" will do fine, since the 'T' is clearly non-coding and can be ignored.
The first letter after that, which also indicates a rank, indicates the starting rank. Again, this does not have to - but may! - be the very next letter. In "The", the 'e' might mean '2', or it might be a blank and the first letter of the next word could indicate rank.
Repeat this - including blanks sufficient to create a reasonable-looking text message - with the destination file and rank. Make sure to switch encodings at times. Voilà, instant deniability.
For extra points, you can either have several letters standing for one rank or file, the same letters standing for both ranks and files, or whatever mix you want. More encoding letters means more possible coding words but fewer possible blanks, and vice versa - something is to be said for either option.
Really, the only possibility to stop this - as well as the only choice for sanity and proper behaviour - is to forbid, or even block, mobile phones in the venue.
Now all we have to do is get all trains declared chess playing venues, and the world will be a better place.
Richard