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Date: Mon, 20 Aug 2001 12:47:56 +0200
From: Martin Dalecki <dalecki@evision-ventures.com>
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To: Johan Adolfsson <johan.adolfsson@axis.com>
CC: Robert Love <rml@tech9.net>, Oliver Xymoron <oxymoron@waste.org>,
        linux-kernel@vger.kernel.org, riel@conectiva.com.br
Subject: Re: [PATCH] let Net Devices feed Entropy, updated (1/2)
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Johan Adolfsson wrote:
> 
> Martin Dalecki <dalecki@evision-ventures.com> wrote:
> > I think you are just wrong - nobody really needs this patch. /dev/random
> > or /dev/urandom ar *both* anyway just complete overkill in terms of
> > practical security. /dev/urandom is in esp silly, since it is providing
> > a md5 hash implementation inside the kernel, which could be *compleatly*
> and
> > entierly done inside user land.
> 
> And I think you are wrong, this patch is needed.
> Keep up the good work Robert!
> 
> > You mean - there is no known algorithm with polynomial time
> > behaviour enabling us to calculate the next value of this function
> > from the previous ones - Not more nor less - no pysics and
> > entropy involved. If you assume this holds true it's mathematically
> > entierly sufficient that a single only seed value is not known.
> 
> Where would you get the single seed from in an embedded head
> less system if you don't have a hardware random generator,
> no disk and don't seed it from the network interrupts?

The device get's powerd up at a random time for the attacker.
That's entierly sufficient if you assume that your checksum function
f(i) hat the property that there is no function g, where we have
f(i+1)=g(f(i)), where g has a polynomial order over the time domain.
i is unknown for the attacker.