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

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Message-ID: <475EAFF9.9020405@tmr.com>
Date:	Tue, 11 Dec 2007 10:42:49 -0500
From:	Bill Davidsen <davidsen@....com>
To:	Adrian Bunk <bunk@...nel.org>
CC:	Marc Haber <mh+linux-kernel@...schlus.de>,
	linux-kernel@...r.kernel.org
Subject: Re: Why does reading from /dev/urandom deplete entropy so much?

Adrian Bunk wrote:
> On Thu, Dec 06, 2007 at 02:32:05PM -0500, Bill Davidsen wrote:
>   
>> ...
>> Sounds like a local DoS attack point to me...
>>     
>
> As long as /dev/random is readable for all users there's no reason to 
> use /dev/urandom for a local DoS...
>   

The original point was that urandom draws entropy from random, and that 
it is an an inobvious and unintentional drain on the entropy pool. At 
least that's how I read it. I certainly have programs which draw on 
urandom simply because it's a convenient source of meaningless data. I 
have several fewer since this discussion started, though, now that I 
have looked at the easy alternatives.

-- 
Bill Davidsen <davidsen@....com>
  "Woe unto the statesman who makes war without a reason that will still
  be valid when the war is over..." Otto von Bismark 


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