From: Jeff King <peff@peff.net>
To: "brian m. carlson" <sandals@crustytoothpaste.net>
Cc: git@vger.kernel.org
Subject: Re: [PATCH 0/2] Generate temporary files using a CSPRNG
Date: Tue, 16 Nov 2021 10:44:33 -0500 [thread overview]
Message-ID: <YZPR4Ya1ocWvKbAf@coredump.intra.peff.net> (raw)
In-Reply-To: <20211116033542.3247094-1-sandals@crustytoothpaste.net>
On Tue, Nov 16, 2021 at 03:35:40AM +0000, brian m. carlson wrote:
> For those who are interested, I computed the probability of spurious
> failure for the self-test mode like so:
>
> 256 * (255/256)^65536
>
> This Ruby one-liner estimates the probability at approximately 10^-108:
>
> ruby -e 'a = 255 ** 65536; b = 256 ** 65536; puts b.to_s.length - a.to_s.length - 3'
>
> If I have made an error in the calculation, please do feel free to point
> it out.
Yes, I think your math is correct there.
A more interesting question is whether generating 64k of PRNG bytes per
test run is going to a problem for system entropy pools. For that
matter, I guess the use of it for tempfiles will produce a similar
burden, since we run so many commands. My understanding is that modern
systems will just produce infinite output for /dev/urandom, etc, but I
wonder if there are any systems left where that is not true (because
they have a misguided notion that they need to stir in more "real"
entropy bits).
-Peff
next prev parent reply other threads:[~2021-11-16 15:44 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-16 3:35 [PATCH 0/2] Generate temporary files using a CSPRNG brian m. carlson
2021-11-16 3:35 ` [PATCH 1/2] wrapper: add a helper to generate numbers from " brian m. carlson
2021-11-16 15:31 ` Jeff King
2021-11-16 16:01 ` rsbecker
2021-11-16 18:22 ` Taylor Blau
2021-11-16 19:58 ` rsbecker
2021-11-16 22:41 ` brian m. carlson
2021-11-16 23:20 ` rsbecker
2021-11-17 0:47 ` Carlo Arenas
2021-11-17 3:05 ` rsbecker
2021-11-17 1:03 ` brian m. carlson
2021-11-17 1:50 ` Carlo Arenas
2021-11-17 3:04 ` Jeff King
2021-11-17 3:12 ` rsbecker
2021-11-17 3:36 ` Carlo Arenas
2021-11-17 20:01 ` Jeff King
2021-11-17 20:19 ` rsbecker
2021-11-17 23:30 ` brian m. carlson
2021-11-17 23:34 ` rsbecker
2021-11-17 3:03 ` rsbecker
2021-11-17 7:39 ` Junio C Hamano
2021-11-17 23:01 ` brian m. carlson
2021-11-18 7:19 ` Junio C Hamano
2021-11-18 22:16 ` brian m. carlson
2021-11-22 9:10 ` Junio C Hamano
2021-11-16 3:35 ` [PATCH 2/2] wrapper: use a CSPRNG to generate random file names brian m. carlson
2021-11-16 15:36 ` Jeff King
2021-11-16 18:28 ` Taylor Blau
2021-11-16 18:57 ` Junio C Hamano
2021-11-16 19:21 ` Jeff King
2021-11-16 19:33 ` Taylor Blau
2021-11-16 15:44 ` Jeff King [this message]
2021-11-16 22:17 ` [PATCH 0/2] Generate temporary files using a CSPRNG brian m. carlson
2021-11-16 22:29 ` rsbecker
2021-11-16 20:35 ` Ævar Arnfjörð Bjarmason
2021-11-16 21:06 ` Jeff King
2021-11-17 8:36 ` Ævar Arnfjörð Bjarmason
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