Date: Wed, 7 Jun 2000 23:44:02 -0700 (PDT) From: Kris Kennaway <kris@FreeBSD.org> To: Mark Murray <mark@grondar.za> Cc: current@FreeBSD.ORG Subject: Re: mktemp() patch Message-ID: <Pine.BSF.4.21.0006072338550.73192-100000@freefall.freebsd.org> In-Reply-To: <200006080629.IAA04362@grimreaper.grondar.za>
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On Thu, 8 Jun 2000, Mark Murray wrote:
> Hi
>
> > + /* Encode the PID (with 1 bit of randomness) into 3 base-64 chars */
> > + pid = getpid() | (arc4random() & 0x00020000);
>
> What is the purpose of this? It looks hugely wasteful to me. If you
> really need a single random bit, it is not good to waste a block of
> hard-gained gryptographic randomness; can you not use a pseudo-random
> bit-generator?
arc4random() does not consume entropy except the first time it is called
and when explicitly reseeded through arc4random_stir(). Apart from that
it's a deterministic function (the arc4 stream cipher), but it's still a
reasonably good cryptographic PRNG because arc4 is a cryptographically
strong algorithm.
Kris
--
In God we Trust -- all others must submit an X.509 certificate.
-- Charles Forsythe <forsythe@alum.mit.edu>
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