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From: lf-lists@mattcorallo.com
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Date: Tue, 4 Aug 2020 00:02:21 -0400
Message-Id: <4AFF2D6A-57BE-40CF-A15F-E972AEB9ACDE@mattcorallo.com>
References: <20200709214048.27mycsi5h2bnv3cc@erisian.com.au>
In-Reply-To: <20200709214048.27mycsi5h2bnv3cc@erisian.com.au>
To: Anthony Towns <aj@erisian.com.au>,
 Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] BIP 118 and SIGHASH_ANYPREVOUT
Precedence: list

While I admit I haven=E2=80=99t analyzed the feasibility, I want to throw on=
e additional design consideration into the ring.

Namely, it would ideally be trivial, at the p2p protocol layer, to relay a t=
ransaction to a full node without knowing exactly which input transaction th=
at full node has in its mempool/active chain. This is at least potentially i=
mportant for systems like lighting where you do not know which counterparty c=
ommitment transaction(s) are in a random node=E2=80=99s mempool and you shou=
ld be able to describe to that node that you are spending then nonetheless.

This is (obviously) an incredibly nontrivial problem both in p2p protocol co=
mplexity and mempool optimization, but it may leave SIGHASH_NOINPUT rather u=
seless for lighting without it.

The least we could do is think about the consensus design in that context, e=
ven if we have to provide an external overlay relay network in order to make=
 lighting transactions relay properly (presumably with miners running such s=
oftware).

Matt

> On Jul 9, 2020, at 17:46, Anthony Towns via bitcoin-dev <bitcoin-dev@lists=
.linuxfoundation.org> wrote:
>=20
> =EF=BB=BFHello world,
>=20
> After talking with Christina ages ago, we came to the conclusion that
> it made more sense to update BIP 118 to the latest thinking than have
> a new BIP number, so I've (finally) opened a (draft) PR to update BIP
> 118 with the ANYPREVOUT bip I've passed around to a few people,
>=20
> https://github.com/bitcoin/bips/pull/943
>=20
> Probably easiest to just read the new BIP text on github:
>=20
> https://github.com/ajtowns/bips/blob/bip-anyprevout/bip-0118.mediawiki
>=20
> It doesn't come with tested code at this point, but I figure better to
> have the text available for discussion than nothing.
>=20
> Some significant changes since previous discussion include complete lack
> of chaperone signatures or anything like it (if you want them, you can
> always add them yourself, of course), and that ANYPREVOUTANYSCRIPT no
> longer commits to the value (details/rationale in the text).
>=20
> Cheers,
> aj
>=20
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