Date: Mon, 4 Jan 2021 16:43:59 -0500 From: Ryan Stone <rysto32@gmail.com> To: Poul-Henning Kamp <phk@phk.freebsd.dk> Cc: John-Mark Gurney <jmg@funkthat.com>, RW <rwmaillists@googlemail.com>, FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: HEADS UP: FreeBSD src repo transitioning to git this weekend Message-ID: <CAFMmRNzvEJry6FfcjUEw5ciq=FaRHm9PRBX%2BNGNuOwZhwDPPZg@mail.gmail.com> In-Reply-To: <95361.1609793029@critter.freebsd.dk> 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> <95361.1609793029@critter.freebsd.dk>
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On Mon, Jan 4, 2021 at 3:44 PM Poul-Henning Kamp <phk@phk.freebsd.dk> wrote: > 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.) FWIW, a coworker of mine had a little hobby of introducing commits into our internal repro that had hashes that all started with deadc0de. As I understand it, it was able to do this by adding an bogus attribute with the right value to the commit object. Now, brute-forcing 8 digits in the hash is one thing and doing it for all 40 is quite another, but I suspect that this demonstrates that it's *possible* to do it for a git hash, given enough computing resources.
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