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Date: Sun, 30 Aug 2009 14:07:27 +0200
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From: Heinz Diehl <htd@fancy-poultry.org>
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Subject: Re: [dm-crypt] Random fill
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At Sat, 29 Aug 2009 15:58:58 -0400,
Stroker wrote:

> My question is, wouldn't the following command fill my 
> drives with randommess?  Much more quickly than urandom?
 
> dd if=/dev/zero of=/dev/mapper/encrypted_sdb1

Yes, with pseudorandomness just like urandom, as far as I know.
 
> Perhaps change the key afterward, or even delete/rebuild 
> the dm-crypt block?

You can overwrite the LUKS header multiple times and set up a new one.

Btw: why do you want to overwrite the entire partition? In my eyes, this is
some kind of rocket science and makes no sense, considering Kerckhoff's law.