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

From: pushd <[email-masked]>
Date: Fri, 22 Apr 2022 17:14:50 +0000

Hi Luke,

> But none of this ST nonsense, please. That alone is a reason to oppose it.

Agree. Any soft fork that uses only speedy trial should be opposed. There are few other reasons to oppose it as well:

- Premature idea
- Use cases are not interesting for all users
- 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

I am planning to maintain a page for all the NACKs against BIP 118 based on this thread. I am assuming you don't mind including your name in it.

pushd

---
parallel lines meet at infinity?

> ------------------------------
>
> Message: 3
> Date: Fri, 22 Apr 2022 17:01:14 +0000
> From: Luke Dashjr [email-masked]
>
> To: [email-masked], darosior
> [email-masked]
>
> Subject: Re: [bitcoin-dev] ANYPREVOUT in place of CTV
> Message-ID: [email-masked]
>
> Content-Type: Text/Plain; charset="iso-8859-1"
>
> There's no reason for before/after/in place. We have version bits specifically
> so we can have multiple deployments in parallel.
>
> But none of this ST nonsense, please. That alone is a reason to oppose it.
>
> Luke
>
> On Friday 22 April 2022 11:11:41 darosior via bitcoin-dev 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.
>>
>> 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-me
>> ssage.
>>
>> [1] https://anyprevout.xyz/ "Use Cases" section
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>> [email-masked]
>> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
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