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Date: Thu, 21 Nov 2002 23:39:11 -0500
From: Jeff Garzik <jgarzik@pobox.com>
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To: "Albert D. Cahalan" <acahalan@cs.uml.edu>
CC: linux-kernel@vger.kernel.org, kentborg@borg.org, alan@lxorguk.ukuu.org.uk
Subject: Re: Where is ext2/3 secure delete ("s") attribute?
References: <200211220241.gAM2fEZ357378@saturn.cs.uml.edu>
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Albert D. Cahalan wrote:

> Jeff Garzik writes:
>
> >Albert D. Cahalan wrote:
>
>
> >>Forget the shred program. It's less useful than having the
> >>filesystem simply zero the blocks, because it's slow and you
> >>can't be sure to hit the OS-visible blocks.
> >
> >Why not?
> >
> >Please name a filesystem that moves allocated blocks around on you.  And
> >point to code, too.
>
>
> Reiserfs tails
>   fs/reiserfs


inodes don't move

> ext3 with data journalling
>   fs/ext3


the allocated blocks don't change


> the journalling flash filesystems
>   fs/jffs
>   fs/jffs2


yep

> NTFS with compression
>   fs/ntfs


the allocated blocks don't change


> Multiple overwrites won't protect you from the disk manufacturer
> or the NSA. Only one is needed to protect against root & kernel.
> So it makes sense to have the filesystem zero the blocks when
> they are freed from a file.


if you need to protect against root, then zeroing the blocks isn't going 
to help for LVM or jffs or other journalling.

	Jeff


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