Re: Unswappable memory needed is user space
Zow (zow@torii.bruggerink.com)
Tue, 08 Dec 1998 09:23:04 -0800
> I'm making a crypto program (under french law).
> It crypts a file and then totally erase the uncrypted by filling it with
> zero.
>
Don't know about the non-swap mem, but what you're doing here is another
problem. Just writting zeros to the disk won't prevent the file from still
being read off the disk by some very syphisicated techniques (done by looking
at the magnetic fields on the platter in a clean box). Instead, you want to
write over the file at least three times with random bits. This too may be
insufficient if ext2 (or whatever other underlying fs) relocates the file when
you go to write over it (hence, the origional is in one place, marked as free
space, and your random data is in another). Anyone know more about this?
>
> christophe leroy
>
-"Zow"
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