Date: Sat, 10 Jun 2000 09:13:30 +0200 From: Mark Murray <mark@grondar.za> To: "Andrey A. Chernov" <ache@FreeBSD.ORG> Cc: Mark Murray <mark@grondar.za>, "Jeroen C. van Gelderen" <jeroen@vangelderen.org>, Kris Kennaway <kris@FreeBSD.ORG>, current@FreeBSD.ORG Subject: Re: mktemp() patch Message-ID: <200006100713.JAA04771@grimreaper.grondar.za> In-Reply-To: <20000609155342.B33329@freebsd.org> ; from "Andrey A. Chernov" <ache@FreeBSD.ORG> "Fri, 09 Jun 2000 15:53:42 MST." References: <20000609155342.B33329@freebsd.org>
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> > Why not just XOR the whole lot into the current ${randomnumber}?
> > That way, at least the effort of the whole calculation is not wasted
> > as much.
>
> Why to XOR true random bits from arc4random() with non-random bits from
> getpid()? It only weakens. Better way is just remove any getpid() code and
> left arc4random() only.
Rubbish. A XOR B is random if at least one of A or B is random.
That is a pretty fundamental theorem of Cryptography. My suggestion
_strengthens_ the random number. All you lose is one bit if it
turns out that BOTH A and B are random, because they get combined
into one.
M
--
Mark Murray
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