Re: [bitcoin-dev] ANYPREVOUT in place of CTV

From: "Hampus Sjöberg" <hampus.sjoberg@gmail•com>
To: Bitcoin Protocol Discussion <bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] ANYPREVOUT in place of CTV
Date: Mon, 25 Apr 2022 17:34:25 +0400	[thread overview]
Message-ID: <CAFMkqK-pHDcXvSUrEyzrS8OsmW-0xa2o=MGYq3o_awXmnANc_Q@mail.gmail.com> (raw)
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Hi pushd.
Would you mind clarifying what you mean by BIP118 being a premature idea?
SIGHASH_ANYPREVOUT, or SIGHASH_NOINPUT, as it was called back then, was
first proposed in the original Lightning Network whitepaper back in 2015.
It has been discussed on and off for many years now. I would not call it a
premature idea.

Now, the revised "Taprooted" version called ANYPREVOUT is a couple of years
old, so going with the NOINPUT version could be a safer bet (though that's
a bit ridiculous in my opinion).

Regarding that you do not find use-cases interesting. That's all fine I
suppose, but in the Lightning Network scene, I think it's fair to say that
there's widespread enthusiasm in getting a working eltoo solution, which
necessitates something like NOINPUT/ANYPREVOUT.
And even if eltoo wouldn't happen, enabling spacechains, covenants and
blind statechains seem like sufficient use-cases to me.

Cheers
Hampus

On Fri, Apr 22, 2022 at 9:32 PM pushd via bitcoin-dev <
bitcoin-dev@lists•linuxfoundation.org> wrote:

> I would like to know people's sentiment about doing (a very slightly
> tweaked version of) BIP118 in place of (or before doing) BIP119.
>
>
> NACK for the below reasons:
>
> - Premature idea
> - I do not find use cases interesting
> - We are still in research phase of implementing covenants in bitcoin and
> looking for the best proposal
> - Taproot soft fork was recently activated and its too soon
> - Not enough documentation available
> - Could not find any pull request in core for BIP 118 that can be reviewed
> - Not enough tools available for testing
>
>
> pushd
> ---
>
> parallel lines meet at infinity?
>
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> On Friday, April 22nd, 2022 at 5:30 PM,
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> 1. ANYPREVOUT in place of CTV (darosior)
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> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 22 Apr 2022 11:11:41 +0000
> From: darosior darosior@protonmail•com
>
> To: Bitcoin Protocol Discussion
> bitcoin-dev@lists•linuxfoundation.org
>
> Subject: [bitcoin-dev] ANYPREVOUT in place of CTV
> Message-ID:
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>
> I would like to know people's sentiment about doing (a very slightly
> tweaked version of) BIP118 in place of
> (or before doing) BIP119.
>
> SIGHASH_ANYPREVOUT and its precedent iterations have been discussed for
> over 6 years. It presents proven and
> implemented usecases, that are demanded and (please someone correct me if
> i'm wrong) more widely accepted than
> CTV's.
>
> SIGHASH_ANYPREVOUTANYSCRIPT, if its "ANYONECANPAY" behaviour is made
> optional [0], can emulate CTV just fine.
> Sure then you can't have bare or Segwit v0 CTV, and it's a bit more
> expensive to use. But we can consider CTV
> an optimization of APO-AS covenants.
>
> CTV advocates have been presenting vaults as the flagship usecase.
> Although as someone who've been trying to
> implement practical vaults for the past 2 years i doubt CTV is necessary
> nor sufficient for this (but still
> useful!), using APO-AS covers it. And it's not a couple dozen more virtual
> bytes that are going to matter for
> a potential vault user.
>
> If after some time all of us who are currently dubious about CTV's stated
> usecases are proven wrong by onchain
> usage of a less efficient construction to achieve the same goal, we could
> roll-out CTV as an optimization. In
> the meantime others will have been able to deploy new applications
> leveraging ANYPREVOUT (Eltoo, blind
> statechains, etc..[1]).
>
> Given the interest in, and demand for, both simple covenants and better
> offchain protocols it seems to me that
> BIP118 is a soft fork candidate that could benefit more (if not most of)
> Bitcoin users.
> Actually i'd also be interested in knowing if people would oppose the
> APO-AS part of BIP118, since it enables
> CTV's features, for the same reason they'd oppose BIP119.
>
> [0] That is, to not commit to the other inputs of the transaction (via
> sha_sequences and maybe also
> sha_amounts). Cf
> https://github.com/bitcoin/bips/blob/master/bip-0118.mediawiki#signature-message
> .
>
> [1] https://anyprevout.xyz/ "Use Cases" section
>
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