From: "Russell O'Connor" <roconnor@blockstream•io>
To: Peter Todd <pete@petertodd•org>,
Bitcoin Protocol Discussion
<bitcoin-dev@lists•linuxfoundation.org>
Cc: Steve Davis <steven.charles.davis@gmail•com>
Subject: Re: [bitcoin-dev] SHA1 collisions make Git vulnerable to attakcs by third-parties, not just repo maintainers
Date: Sat, 25 Feb 2017 15:53:12 -0500 [thread overview]
Message-ID: <CAMZUoK=sq_sRoXuySca-VAGwA3AzeoZ5iNFSnKULbj+NtPjHFA@mail.gmail.com> (raw)
In-Reply-To: <20170225191201.GA15472@savin.petertodd.org>
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On Sat, Feb 25, 2017 at 2:12 PM, Peter Todd via bitcoin-dev <
bitcoin-dev@lists•linuxfoundation.org> wrote:
> On Sat, Feb 25, 2017 at 11:10:02AM -0500, Ethan Heilman via bitcoin-dev
> wrote:
> > >SHA1 is insecure because the SHA1 algorithm is insecure, not because
> > 160bits isn't enough.
> >
> > I would argue that 160-bits isn't enough for collision resistance.
> Assuming
> > RIPEMD-160(SHA-256(msg)) has no flaws (i.e. is a random oracle),
> collisions
>
> That's something that we're well aware of; there have been a few
> discussions on
> this list about how P2SH's 160-bits is insufficient in certain use-cases
> such
> as multisig.
>
> However, remember that a 160-bit *security level* is sufficient, and
> RIPEMD160
> has 160-bit security against preimage attacks. Thus things like
> pay-to-pubkey-hash are perfectly secure: sure you could generate two
> pubkeys
> that have the same RIPEMD160(SHA256()) digest, but if someone does that it
> doesn't cause the Bitcoin network itself any harm, and doing so is
> something
> you choose to do to yourself.
>
Be aware that the issue is more problematic for more complex contracts.
For example, you are building a P2SH 2-of-2 multisig together with someone
else if you are not careful, party A can hand their key over to party B,
who can may try to generate a collision between their second key and
another 2-of-2 multisig where they control both keys. See
https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2016-January/012205.html
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next prev parent reply other threads:[~2017-02-25 20:53 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <mailman.22137.1487974823.31141.bitcoin-dev@lists.linuxfoundation.org>
2017-02-24 23:49 ` Steve Davis
2017-02-25 1:01 ` Peter Todd
2017-02-25 12:04 ` Steve Davis
2017-02-25 14:50 ` Leandro Coutinho
2017-02-25 16:10 ` Ethan Heilman
2017-02-25 17:45 ` Shin'ichiro Matsuo
2017-02-27 9:15 ` Henning Kopp
2017-02-25 18:19 ` Alice Wonder
2017-02-25 18:36 ` Ethan Heilman
2017-02-25 19:12 ` Peter Todd
2017-02-25 20:42 ` Watson Ladd
2017-02-25 20:57 ` Peter Todd
2017-02-25 20:53 ` Russell O'Connor [this message]
2017-02-25 21:04 ` Peter Todd
2017-02-25 21:21 ` Dave Scotese
2017-02-25 21:34 ` Steve Davis
2017-02-25 21:40 ` Peter Todd
2017-02-25 21:54 ` Steve Davis
2017-02-25 22:14 ` Pieter Wuille
2017-02-25 22:34 ` Ethan Heilman
2017-02-26 6:26 ` Steve Davis
2017-02-26 6:36 ` Pieter Wuille
2017-02-26 7:16 ` Steve Davis
[not found] ` <CAPg+sBirowtHqUT5GUJf9hmDEACKVX19HAon-rrz7GmO8OBsNg@mail.gmail.com>
2017-02-26 16:53 ` Steve Davis
2017-02-25 23:09 ` Leandro Coutinho
2017-02-23 18:14 Peter Todd
2017-02-23 21:28 ` Peter Todd
2017-02-23 23:57 ` Aymeric Vitte
2017-02-24 10:04 ` Tim Ruffing
2017-02-24 15:18 ` Aymeric Vitte
2017-02-24 16:30 ` Tim Ruffing
2017-02-24 17:29 ` Aymeric Vitte
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