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Date:      Thu, 23 May 1996 10:21:07 -0600
From:      Warner Losh <imp@village.org>
To:        Paul Traina <pst@shockwave.com>
Cc:        Garrett Wollman <wollman@lcs.mit.edu>, Poul-Henning Kamp <phk@critter.tfs.com>, current@FreeBSD.ORG, blh@nol.net
Subject:   Re: freebsd + synfloods + ip spoofing 
Message-ID:  <199605231621.KAA10068@rover.village.org>
In-Reply-To: Your message of Thu, 23 May 1996 09:14:01 PDT

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: That offers no improvement over just randomization.

As long as the randomization isn't predictible, yes.  I'm not sure why
they suggest the MD-5 hash.

I wrote:
:   Per attempt is easy to ramdomize w/o violating 793 since you still
:   have 2^31 bits of randomness that you can use (since the original
         31 bits

Paul again:
: However, the random number generator that we're using could be badly broken,
: which is why I want to get BHL's tools and verify his tests.

If it is a pseudo random number sequence generater, then it buys you
nothing over += 30 because it is predictible (even if it is uniform
and looks random).  I've not tkaen a look at the code to know for sure
if the randomness is good enough or not.  Likely you need to do a
/dev/random sort of thing that will be both uniform and unpredictable.

Warner

P.S.  /dev/random here is a entropy gatherer in the kernel for the
purpose of generating cryptographically strong random numbers.
-stable doesn't seem to have this, not sure about -current.  Linux
does which is where I'm getting the nomenclature from.



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