bugtraq - Re: Peter Gutmann data deletion theaory?

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Date: Sat, 23 Jul 2005 14:26:06 +0300
From: "Alexander L. Ivanchev" <alexander@...nchev.org>
To: Volker Tanger <vtlists@...e.de>
Cc: bugtraq@...urityfocus.com
Subject: Re: Peter Gutmann data deletion theaory?

[Re-sending in plain-text]

Hello Volker,

> 1. writing zeroes all over
> 2. low level format

I cannot believe the concept of "low-level" format as a last resort 
measure is still considered to be anything else, but "zeroing" out a 
drive. Modern IDE drives are only, truly LLF'ed at factory-level. A long 
time ago, in the world of RLL/MFM disks it was possible to define 
interleave levels, etc., and actually re-create the physical tracks on 
the platter. Not any more.

Personally, in the modern world, I've been hearing more and more of the 
application HDD degaussers to the end of data wiping. I'd be more 
interested in actual research on the extent of data recovery after a 
thorough demagnetization via specialized hardware... Has anyone done 
this kind of research?

Thanks,
Alexander

Volker Tanger wrote:

>Greetings!
>
>On Thu, 21 Jul 2005 14:07:12 -0500
>Simple Nomad <thegnome@...c.org> wrote:
>  
>
>>On Wednesday 20 July 2005 18:48, Jared Johnson wrote:
>>    
>>
>>>Data overwritten once or twice
>>>      
>>>
>[...] 
>  
>
>>The quote is from 1996. I spoke with Guttman about this at AusCERT a
>>few years  ago and even *he* doesn't believe it anymore. Drive
>>technology has changed  substantially since then.
>>    
>>
>
>His theory no longer does hold true. His 1996 paper is available at
>http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html, targeting
>MFM and RLL disk technology, where a typical 5.25" disk held 20-80MB
>(yes, MEGAbyte, not GB). His recommendations were based on old magnetic
>disc technology where each bit was represented by the magnetical
>orientation on the platter (north=1, south=0). After that came other
>technologies, where bits are defined by changes of the magnetic field
>even down to probabilistic field measurements - which allowes tighter
>data packing but rendered the base of his recommendations useless.
>
>Of course - if you write often enough with different data over "the
>same" spot, the original data will become more and more unreadable.
>
>OTOH I have seen one company with a *really* thorough disk & tape 
>cleaning technique: 
>
>	1. writing zeroes all over
>	2. low level format
>	3. shredding the disc drive into small pieces
>	4. magnet treatment of the scrap metal
>	5. burning in their own waste incinerating plant
>
>For "home use" a grinder/raw polish/sandblast treatment of both platter
>sides should be fine, too...   ;-)
>
>Bye
>
>Volker
>
>
>  
>

-- 
Sincerely,
Mr. Alexander L. Ivanchev

Phone/Fax: +359 2 929-3984
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