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From: Steve Davis <steven.charles.davis@gmail.com>
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To: Peter Todd <pete@petertodd.org>
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Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] SHA1 collisions make Git vulnerable to attakcs by
third-parties, not just repo maintainers
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> On Feb 24, 2017, at 7:01 PM, Peter Todd <pete@petertodd.org> wrote:
>=20
> On Fri, Feb 24, 2017 at 05:49:36PM -0600, Steve Davis via bitcoin-dev =
wrote:
>> If the 20 byte SHA1 is now considered insecure (with good reason), =
what about RIPEMD-160 which is the foundation of Bitcoin addresses?
>=20
> SHA1 is insecure because the SHA1 algorithm is insecure, not because =
160bits isn't enough.
>=20
> AFAIK there aren't any known weaknesses in RIPEMD160,
=E2=80=A6so far. I wonder how long that vacation will last?
> but it also hasn't been
> as closely studied as more common hash algorithms.
...but we can be sure that it will be, since the dollar value held in =
existing utxos continues to increase...
> That said, Bitcoin uses
> RIPEMD160(SHA256(msg)), which may make creating collisions harder if =
an attack
> is found than if it used RIPEMD160 alone.
Does that offer any greater protection? That=E2=80=99s not so clear to =
me as the outputs (at least for p2pkh) only verify the public key =
against the final 20 byte hash. Specifically, in the first (notional) =
case the challenge would be to find a private key that has a public key =
that hashes to the final hash. In the second (realistic) case, you =
merely need to add the sha256 hash into the problem, which doesn=E2=80=99t=
seem to me to increase the difficulty by any significant amount?=20
/s=
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