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Re: [vox-tech] Most efficient way to wipe hard drives
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Re: [vox-tech] Most efficient way to wipe hard drives

Good morning All,
Is anyone familiar with C Unix

-----Original Message-----
From: vox-tech-bounces@lists.lugod.org
[mailto:vox-tech-bounces@lists.lugod.org] On Behalf Of Chanoch (Ken)
Sent: Thursday, September 10, 2009 10:38 AM
To: lugod's technical discussion forum
Subject: Re: [vox-tech] Most efficient way to wipe hard drives

On Thu, Sep 10, 2009 at 09:56:54AM -0700, Brian Lavender wrote:
> On Wed, Sep 09, 2009 at 09:20:30PM -0700, Bill Broadley wrote:
> > 
> > Short answer, one wipe is enough (At least for NIST, and one of the
> > Infosec standards), wipes miss bad sectors, the ATA secure erase
command is
> > worth checking out.
> [snip]
> I think caching is a concern on some systems, so more wipes seems to
> magically make the write go to the actual media. But I would agree
> one wipe is probably enough. I had not thought about bad blocks. 
> > 
> > So if you don't use secure wipe and won't lose sleep at night over a
few bad
> > blocks being potentially recovered I'd recommend something like:
> > 
> > dd if=/dev/urandom of=/dev/sd<whichever disk>
> Your computer must have a lot of entropy! Note that that device
> entropy from the system. When an event happens, it may be worth one or
> two bits. Last time I wrote a program that read from that device, it
> seemed that I got a number of bytes, and then I had to wait as various
> events occured to the system. That is why they often tell you to move
> mouse around when generating keys. It generates entropy for the

/dev/random, blocks waiting for entropy.
/dev/urandom doesn't wait for entropy. It uses entropy if it's
avalable, and switches to a PRNG if there isn't enough entropy. I
think it's similar to what you suggest doing with AES.


Chanoch (Ken) Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
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