Extremely weak under an active attack: 'sed s/\([^ ]\) */\1 /g' What you want is something that cannot be easily removed from the message without also affectin

Extremely weak under an active attack: 'sed s/\([^ ]\) */\1 /g' What you want is something that cannot be easily removed from the message without also affecting the meaning of the cover message. I am thinking of some sort of encoding that uses orthographic errors that are not trivial to fix automatically (e.g. substitute words with valid homophones, instead of changing individual characters). That would be still easy to detect, so you probably need a very low bandwidth channel to make it indistinguishable from a typical text with mistakes. Doing this with multimedia is probably far easier.