I know, shred allowes to choose any file to take random bytes from it. However, there is still one issue, which I found both in articles and rumors about secure erasing: the fact itself of using such data removal could be sensitive, and with current approaches (using any of random, patterns or zero data) it is non-trivial to hide.
Thus, another approach came to my mind - use entire files or their relatively chunks to overwrite. Following options could present: - path/file set, allowed as source - siilar to most file search indexers like locate, baloo or tracker; - chunk size range, min and max. If max is unset (e.g. =-1), it would mean unlimited maximum size; - In addition to first - may be have some "weight" kind for different paths (even inside anothers), affecting their final priority. Sure it looks pretty complex, but imho - what yet ever could least suspicious, than it unwanted area are "uncarefully" get overwritten during usual file copy/backup ops, due to some fs "bug" :).
