Security Basics: RE: Hard Drive data security

[Atom 'Smasher' <atom () suspicious org>]

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On Tue, 5 Oct 2004, Paris E. Stone wrote:

> I was informed that /dev/null just wrote zeros to the drive and that a 
> better way was multiple passes using random:
> dd if=/dev/urandom of=/dev/had
>
> or maybe /dev/random
>
> Not positive, so many *nixes with their own ways of doing things.
>
> But basically /dev/urandom writes ones and zeros in random fashion.
==========================

typically, on systems that have them, /dev/random is "true" random and 
/dev/urandom is a CSPRNG.
http://en.wikipedia.org/wiki/CSPRNG

what makes /dev/urandom better than /dev/random for wiping a disk is that 
it can generate output a *lot* faster.
if a few passes over a disk from /dev/urandom isn't good enough, use a 
sledgehammer (and safety glasses).

        ...atom

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