Wiping Out Data

[NoOp]

On 03/27/2007 06:36 AM, Tony Arnold wrote:
> 
> Matthew Flaschen wrote:
>> Felipe Figueiredo wrote:
>>> On Tuesday 27 March 2007 07:10:35 Matthew Flaschen wrote:
>>>
>>>  
>>>> That will rewrite the entire drive with gibberish 7 times (this can be
>>>> adjusted).  That should mostly obliterate all data, then reformat the
>>> Is it really different from 
>>>
>>> dd if=/dev/zero of=/dev/sdb
>>>
>>> ? I don't get it, why is it necessary to use random bits, instead of zeroing 
>>> all bytes (including the FATs)?
>> 
>> Simply overwriting the data once does not mean it can't be recovered.
>> The Department of Defense recommends overwriting 7 times with random
>> data.  It is my understanding that shred can do this.  Someone said
>> before that even:
> 
> This i true of magnetic media, because there is always residual
> magnetism that can be read by sophisticated equipment. I'm not sure it's
> true of USB and flash memory, but then I'm not sure how it works, so who
> knows?
> 
> Regards,
> Tony.

You might find this useful:

http://csrc.nist.gov/
[National Institute of Standards & Technology - Computer Security Division]
  http://csrc.nist.gov/publications/nistpubs/index.html
  http://csrc.nist.gov/fasp/
http://www.cs.auckland.ac.nz/~pgut001/
[Peter Gutmann's home page]

In addition to shred (http://www.die.net/doc/linux/man/man1/shred.1.html)
you might want to have a look at scrub as well:
http://www.die.net/doc/linux/man/man1/scrub.1.html
<quote>
STANDARDS
The dod scrub sequence is compliant with the DoD 5220.22-M procedure for
sanitizing removeable and non-removeable rigid disks which requires
overwriting all addressable locations with a character, its complement,
then a random character, and verify. Please refer to the DoD document
for additional constraints.

The nnsa (default) scrub sequence is compliant with a Dec. 2005 draft of
NNSA Policy Letter NAP-14.x (see reference below) for sanitizing
removable and non-removable hard disks, which requires overwriting all
locations with a pseudorandom pattern twice and then with a known
pattern. Please refer to the NNSA document for additional constraints.
</quote>