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

From: pushd <[email-masked]>
Date: Fri, 22 Apr 2022 13:35:11 +0000

> 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, [email-masked] wrote:

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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 [email-masked]
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> To: Bitcoin Protocol Discussion
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> Subject: [bitcoin-dev] ANYPREVOUT in place of CTV
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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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