Re: [PATCH] let Net Devices feed Entropy, updated (1/2)

[Martin Dalecki <dalecki@evision-ventures.com>]

Robert Love wrote:
> 
> On 18 Aug 2001 22:36:00 -0500, Oliver Xymoron wrote:
> > But your claim is there _is_ entropy. If you think there is, go ahead and
> > use it. Via /dev/urandom. Yes, I know it's theoretically not secure, but
> > then neither is what you're proposing.
> 
> I am only continuing this because I want to explain...
> 
> I claim there is entropy from what?  The difference between interrupts
> for net devices?  Everyone agrees that there is.  The issues is that an
> external attacker could influence the interrupts to the net device, and
> thus make some assumptions about the state.  That is why this patch is
> configurable.  Do as you please.  As I said, some people want it or need
> it.

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.

> Again, /dev/urandom is just as "secure" as /dev/random.  Its the same
> pool.  The same stuff.  Except that /dev/random blocks when the entropy
> count hits 0.
> 
> Now, this count is purely theoretical, too.  Its an estime of the amount
> of entropy -- lack of determinability -- in the pool of bytes.

Wrong. Don't let you confuse yourself by the way the term entropy is
used in
the documentation of /dev/random - it's an abuse of the mathematical
definition anyway. The more appriopriate term there
would be: signal source variability estimate.

> Even when it reaches 0, since the pool is still unknown (only previous
> output may be known) and the output is hashed, its still pretty much
> undeterminable.  But mathematically and theoretically, our entropy
> estimate says it is not.

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.