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Date: Thu, 17 Jan 2008 11:02:10 +0200
From: Marc Silver <marcs@draenor.org>
To: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>
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Cc: "Jason C. Wells" <jcw@highperformance.net>,
	freebsd general questions <freebsd-questions@freebsd.org>,
	Peter Boosten <peter@boosten.org>
Subject: Re: Gutman Method on Empty Space
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Hi there,

On Thu, Jan 17, 2008 at 09:43:46AM +0100, Wojciech Puchar wrote:
> how? even single write is enough

Not according to the paper that Gutmann wrote:
	http://www.usenix.org/publications/library/proceedings/sec96/full_papers/gutmann/

In short, he says that if you know how the data itself was overwritten
it can be recovered.  If I recall, the DoD standard for the deletion of
data is to overwrite it 3 times.  

Obviously it all comes down to how important the data is that you're
removing, but a single write is not enough if the data needs to be
disposed of 'securely'.

Cheers,
Marc