Re: secure erasure of files?

[Mike Fedyk <mfedyk@matchmail.com>]

On Wed, Feb 13, 2002 at 10:33:33AM +0100, Helge Hafting wrote:
> Andreas Ferber wrote:
> 
> > I don't know if any filesystem currently relocates blocks if you
> > overwrite a file, but it's certainly possible and allowed (everything
> > else except the filesystem itself simply must not care where the data
> > actually ends up on the disk).
> > 
> A log-structured fs will write new blocks everytime, afaik.

Ext3 only does that on truncate in ordered/writeback mode and probably in
data journaling mode too.

> Ext3 with data journalling keeps copies of recently written data
> in the journal.  Now, if you create a "secret" file and then overwrite
> it you'll still find a copy in the journal until the journal wraps
> It may not wrap if the next thing you do is umount/shutdown.
>
> A secure rm must know the fs it works with.  A better solution
> is to overwrite the entire partition with garbage. The only
> perfect way is to destroy the magnetic surfaces though.
>

Yep, very true.

Phycally breaking the drive apart into pieces and then burning should
suffice. 

Mike