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From: "Vladimir D. Seleznev" <>
To: ALT Linux Team development discussions <>
Subject: Re: [devel] hash collision in rpm
Date: Wed, 5 May 2021 17:11:05 +0300
Message-ID: <YJKneWALLbH3iqIT@portlab> (raw)
In-Reply-To: <>

On Wed, May 05, 2021 at 08:40:27AM +0300, Alexey Tourbin wrote:
> [skip]
> So the expected number of collisions for short versions is smaller,
> but we have two of them. By the linearity of expectation, the birthday
> collision rate is the same. (This generally shows that it is pointless
> to split a long set-version into a few shorter ones, under any classes
> of equivalence on symbols such as ELF ABI tags. Counterintuitively,
> you can't fight birthday collisions by partitioning, unless you also
> increase the output length. So doing separate set-versions for
> and is not necessarily a
> good idea, we can just as well hash sym@FOO_1.0 and sym@FOO_1.1 and
> package them into a single version.)

Unfortunately, the symbol resolution is very flexible (some treat it as
an advantage), so the dynamic linker can resolve sym@FOO_1.0 as sym and
vice versa. That makes almost no point to hash symbols with their

   Vladimir D. Seleznev

      parent reply	other threads:[~2021-05-05 14:11 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-01  9:04 ` [devel] rust-1:1.50.0-alt1: Sisyphus/x86_64 test rebuild failed Alexey Gladkov
2021-05-04 10:32   ` [devel] hash collision in rpm Anton Farygin
2021-05-04 10:45     ` Alexey Gladkov
2021-05-04 12:50       ` Alexey Tourbin
2021-05-05  5:40         ` Alexey Tourbin
2021-05-05 13:10           ` Dmitry V. Levin
2021-05-05 14:11           ` Vladimir D. Seleznev [this message]

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