linux-kernel - Re: Why does reading from /dev/urandom deplete entropy so much?

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Date:	Sat, 08 Dec 2007 11:33:57 -0600
From:	Mike McGrath <mmcgrath@...hat.com>
To:	Theodore Tso <tytso@....edu>,
	Jon Masters <jonathan@...masters.org>,
	Mike McGrath <mmcgrath@...hat.com>,
	Matt Mackall <mpm@...enic.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Ray Lee <ray@...rabbit.org>, Adrian Bunk <bunk@...nel.org>,
	Marc Haber <mh+linux-kernel@...schlus.de>,
	linux-kernel@...r.kernel.org
Subject: Re: Why does reading from /dev/urandom deplete entropy so much?

Theodore Tso wrote:
> On Sat, Dec 08, 2007 at 02:37:57AM -0500, Jon Masters wrote:
>   
>>> BTW, You may be better off using "uuidgen -t" to generate the UUID in
>>> the smolt RPM, since that will use 12 bits of randomness from
>>> /dev/random, plus the MAC, address and timestamp.  So even if there is
>>> zero randomness in /dev/random, and the time is January 1, 1970, at
>>> least the MAC will contribute some uniqueness to the UUID.
>>>       
>> I haven't checked how uuidgen uses the MAC, but I would suggest that
>> that is not something Fedora should jump at doing - although it would
>> help ensure unique UUIDs, it also contributes to the tinfoil hat
>> responses that usually come up with things like smolt.
>>     
>
> Huh?  What's the concern?  All you are submitting is a list of
> hardware devices in your system.  That's hardly anything sensitive....
>   

We actually had a very vocal minority about all of that which ended up 
putting us in the unfortunate position of generating a random UUID 
instead of using a hardware UUID from hal :-/

    -Mike
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