> ... but that's probably an intractable cryptographic process. Not always. Algorithms that append a hash to a file, preserving the same hash, i.e. hash(s)

> ... but that's probably an intractable cryptographic process. Not always. Algorithms that append a hash to a file, preserving the same hash, i.e. hash(s) == hash(s ++ hash(s)) http://stackoverflow.com/q/4823680/12048 http://stackoverflow.com/q/4823680/12048 A program that prints (though does not contain) a hash of itself: http://www.madore.org/~david/computers/quine.html http://www.madore.org/~david/computers/quine.html (edited for formatting)