We'd need to figure out a way to communicate it in a way that isn't through sight of sound. Noooot exactly and easy task, but not impossible.

[ a pause. ] A friend of mine suggested braille. But that would require anyone who wanted to decode our writing to actually learn braille first. But we could encode a cipher into braille and people could read it through touch. Then as long as they could remember the cipher, we could communicate through a code CERES doesn't know, locking them out. Theoretically.

...I know that sounds waaaaay overly-complicated, but it's the best I've got so far.