It seems that perhaps you misinterpreted what I meant by
"watermarking" data. I *did* mean that the encoded information would
become part of the data and not just be a header/footer that could be
easily stripped off. What accomplishes this reasonably for specific
types of data is an open question. And, how resistant such a mark
would be to tampering is equally unclear.
Work being done at AT&T experiements with shifting lines/words &
manipulating character features to encode a binary signature on a page
of text. I am more interested in "marking" images, video, and audio.
Sorry if I mislead you,
Dave