From: Jeff King <peff@peff.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: Theodore Ts'o <tytso@mit.edu>, "H. Peter Anvin" <hpa@zytor.com>,
David Turner <dturner@twopensource.com>,
Stefan Beller <sbeller@google.com>,
"git@vger.kernel.org" <git@vger.kernel.org>
Subject: Re: Migrating away from SHA-1?
Date: Thu, 14 Apr 2016 22:22:33 -0400 [thread overview]
Message-ID: <20160415022233.GE22112@sigill.intra.peff.net> (raw)
In-Reply-To: <xmqq37qnehrm.fsf@gitster.mtv.corp.google.com>
On Thu, Apr 14, 2016 at 07:18:53PM -0700, Junio C Hamano wrote:
> Jeff King <peff@peff.net> writes:
>
> > [2] Somewhere in the list archive is my patch to find partial
> > collisions like "git commit --sha1=31337", and I did in fact use
> > that micro-optimization. That, along with multi-threading, made it
> > feasible to do 6-8 character prefixes, as I recall.
>
> In our testsuite, we have a test that uses many objects, all of
> which have object names that begin with 10 '0' characters.
Can you give more details on which test? 10 zeroes is 40 bits, which
means that by random chance, only about one in a trillion objects would
match that. We certainly didn't hit that randomly, and it seems like it
would be computationally expensive to have come up with the input for
even one such object, let alone "many".
-Peff
next prev parent reply other threads:[~2016-04-15 2:22 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-12 22:38 Migrating away from SHA-1? H. Peter Anvin
2016-04-12 23:00 ` Stefan Beller
2016-04-12 23:06 ` H. Peter Anvin
2016-04-12 23:15 ` Jeff King
2016-04-12 23:15 ` David Turner
2016-04-12 23:44 ` Jeff King
2016-04-14 1:53 ` Theodore Ts'o
2016-04-14 16:47 ` Joey Hess
2016-04-14 17:23 ` David Turner
2016-04-14 17:28 ` H. Peter Anvin
2016-04-14 22:40 ` Theodore Ts'o
2016-04-15 2:13 ` Jeff King
2016-04-15 2:18 ` Junio C Hamano
2016-04-15 2:22 ` Jeff King [this message]
2016-04-12 23:42 ` Jeff King
2016-04-13 1:03 ` Junio C Hamano
2016-04-13 1:36 ` Jeff King
2016-04-13 1:38 ` H. Peter Anvin
2016-04-13 1:51 ` Duy Nguyen
2016-04-13 1:58 ` H. Peter Anvin
2016-04-15 1:50 ` brian m. carlson
-- strict thread matches above, loose matches on Subject: below --
2016-06-18 2:10 Leo Gaspard
2016-06-18 3:30 ` Eric Wong
2016-06-24 18:17 ` brian m. carlson
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