From: Jeff King <peff@peff.net>
To: Santiago Torres Arias <santiago@nyu.edu>
Cc: Kevin Daudt <me@ikke.info>, git <git@vger.kernel.org>
Subject: Re: SHA-1 chosen-prefix colission attack
Date: Wed, 8 Jan 2020 02:30:42 -0500 [thread overview]
Message-ID: <20200108073042.GD1675456@coredump.intra.peff.net> (raw)
In-Reply-To: <20200107203147.r33c5plp5g7pmxmj@LykOS.localdomain>
On Tue, Jan 07, 2020 at 03:31:48PM -0500, Santiago Torres Arias wrote:
> > > As a side result, this shows that it now costs less than 100k USD to
> > > break cryptography with a security level of 64 bits (i.e. to compute
> > > 264 operations of symmetric cryptography).
>
> Just to clarify:
>
> As a stopgap measure, the collision-detection library of Stevens and Shumow [SS17]
> can be used to detect attack attempts (it successfully detects our attack).
>
> At the end of section 7.0,
And if anyone is curious, you can test your build of Git against their
sample files by running:
$ t/helper/test-tool sha1 <messageA
fatal: SHA-1 appears to be part of a collision attack: 8ac60ba76f1999a1ab70223f225aefdc78d4ddc0
Unfortunately you can't test with actual Git objects, because their
chosen-prefixes don't have object headers. They do estimate that a
classical collision is down to ~11k USD to compute, so maybe we'll see
one eventually. :)
-Peff
prev parent reply other threads:[~2020-01-08 7:30 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-07 17:31 SHA-1 chosen-prefix colission attack Kevin Daudt
2020-01-07 20:31 ` Santiago Torres Arias
2020-01-08 7:30 ` Jeff King [this message]
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