I could be way off here, in fact I probably am, but as far as I know there is a way of embedding text in the .jpg file.
Perhaps this is how it is done, maybe not, but it's something to think about!
It was used in the movie 'Along Came A Spider'
The rich kids in the movie used this method to pass notes around the class,
no-one knew what they were doing, cause it seemed as if they were just sharing pictures.
Don't blame me if I'm totally wrong!!