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Date:      Mon, 04 Jan 2021 20:43:49 +0000
From:      "Poul-Henning Kamp" <phk@phk.freebsd.dk>
To:        John-Mark Gurney <jmg@funkthat.com>
Cc:        RW <rwmaillists@googlemail.com>, freebsd-current@freebsd.org
Subject:   Re: HEADS UP: FreeBSD src repo transitioning to git this weekend
Message-ID:  <95361.1609793029@critter.freebsd.dk>
In-Reply-To: <20210104193237.GD31099@funkthat.com>
References:  <20201218182820.1P0tK%steffen@sdaoden.eu> <20201223023242.GG31099@funkthat.com> <20201223162417.v7Ce6%steffen@sdaoden.eu> <20201229011939.GU31099@funkthat.com> <20201229210454.Lh4y_%steffen@sdaoden.eu> <20201230004620.GB31099@funkthat.com> <CAD2Ti2-4xS5n0%2B1oLOHyFh4%2BOCnwtNAAwMkkWzwRVDnt-xmb1Q@mail.gmail.com> <20201231193908.GC31099@funkthat.com> <CAD2Ti2-dKMOx2-k71UyZs1kAGCXPuVwO9ee861oRFNV=aCfuqA@mail.gmail.com> <20210101165651.7319af5a@gumby.homeunix.com> <20210104193237.GD31099@funkthat.com>

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--------
John-Mark Gurney writes:

> SHAttered[1] (2017) created two valid PDF documents which had the same
> SHA-1 hash.  The issue was that they were able to choose the entire
> document.

Shattered is less impressive when you take into account that you
can stuff as much much garbage into a PDF file as you need, without
affecting the files normal function.

Compact data formats, formats which leave no wiggle-room and do not
offer extension-space for "attic-junk", are much harder to produce
*meaningful* collisions for.

(I take no opinion in where git is on that spectrum.)

This is why I am very sceptical of the recent fashion of "GREASING"
which the TLS WG have invented:  To me that sounds like somebody
is allocating wiggle-room for advanced cryptographic skullduggery.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.



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