From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Jeffrey Walton <noloader@gmail.com>
Cc: "Michal Suchánek" <msuchanek@suse.de>, "Git List" <git@vger.kernel.org>
Subject: Re: SHA-accelerated Git
Date: Mon, 3 Jun 2019 12:14:18 +0200 (CEST) [thread overview]
Message-ID: <nycvar.QRO.7.76.6.1906031211470.48@tvgsbejvaqbjf.bet> (raw)
In-Reply-To: <CAH8yC8n8XN1wKiF4FgTm6xfnRHUDi+1=iuWXE8F91P=7mLNsLg@mail.gmail.com>
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Hi Jeffrey,
On Sun, 2 Jun 2019, Jeffrey Walton wrote:
> On Sun, Jun 2, 2019 at 7:21 AM Michal Suchánek <msuchanek@suse.de> wrote:
> >
> > On Sun, 2 Jun 2019 06:43:07 -0400
> > Jeffrey Walton <noloader@gmail.com> wrote:
> >
> > > I have a lot of experience with cutting in SHA acceleration. I have
> > > no experience with Git.
> >
> > sha1 is dead. Git is planning to move away from it. It will not happen
> > overnight but it probably does not make sense to accelerate it at this
> > point.
> >
> > https://github.com/git/git/blob/next/Documentation/technical/hash-function-transition.txt
>
> SHA-1 has been dead for years. That has not stopped Git yet :)
Even worse. Git has changed from an OpenSSL accelerated SHA-1 to a
collision-detecting SHA-1 (sha1dc).
As long as your accelerated SHA-1 cannot guarantee the same level of
safeguards as sha1dc, there is a negligible likelihood that your patches
will be accepted.
> Comparing against a standard C/C++ implementation, Git will see a 3x to
> 6x speedup depending on the platform and algorithm.
Indeed, this reflects my findings.
It's just that we struck the balance on the other side of performance, in
favor of preventing possible attack vectors as best as we can.
Ciao,
Johannes
prev parent reply other threads:[~2019-06-03 10:14 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-02 10:43 SHA-accelerated Git Jeffrey Walton
2019-06-02 11:21 ` Michal Suchánek
2019-06-02 11:34 ` Jeffrey Walton
2019-06-03 10:14 ` Johannes Schindelin [this message]
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