Re: [bitcoin-dev] Burying CSV and segwit soft fork activations

From: Eric Voskuil <eric@voskuil•org>
To: Peter Todd <pete@petertodd•org>,
	Bitcoin Protocol Discussion
	<bitcoin-dev@lists•linuxfoundation.org>
Cc: John Newbery <john@johnnewbery•com>
Subject: Re: [bitcoin-dev] Burying CSV and segwit soft fork activations
Date: Fri, 16 Aug 2019 13:44:47 -0400	[thread overview]
Message-ID: <2377A2C2-04E6-4128-A756-2909474C423C@voskuil.org> (raw)
In-Reply-To: <20190816160650.artngylrzy2id5tr@petertodd.org>

Thanks for adding this to the record.

And for the record I’ll reiterate here, as I did with BIP90, that this is a hard fork.

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> On Aug 16, 2019, at 12:06, Peter Todd via bitcoin-dev <bitcoin-dev@lists•linuxfoundation.org> wrote:
> 
>> On Fri, Aug 16, 2019 at 11:23:37AM -0400, John Newbery via bitcoin-dev wrote:
>> Once a consensus change has been activated and buried by sufficient work,
>> we consider the height of that change to be historic fact. The exact
>> activation method is no longer of practical interest. In some cases the
>> cause of activation is not even decidable. For example, we know that segwit
>> activated at height 481,824 but it's debatable whether that was due to BIP
>> 9 version bits signaling, BIP 148 UASF, or a combination of the two.
> 
> I just wanted to elaborate on this excellent point:
> 
> This is debatable because Bitcoin is a decentralized, soft-forks are backwards
> compatible, and it's very difficult if not impossible to measure the
> preferences of economically significant nodes. Both the BIP9 version bits
> signalling and the BIP 148 UASF had the same basic effect: enforce segwit.
> Furthermore, the BIP 148 UASF rejected blocks that didn't signal via the BIP9
> version bits.
> 
> We can observe the fact that 100% of known blocks produced after Aug 1st 2017
> have complied with segwit rules, and the BIP9 signalling protocol for segwit.
> But strictly speaking we don't really know why that happened. It's possible
> that miners were running the BIP9 signalling Bitcoin Core release around that
> time. It's also possible that miners were running UASF enforcing software.
> It's possible there was a combination of both. Or even entirely different
> software - remember that some miners produced segwit-valid blocks, but didn't
> actually mine segwit transactions. Each scenario leads to the same externally
> observable outcome.
> 
> Furthermore there's the question as to why miners were producing
> segwit-compliant blocks: perhaps they thought the vast majority of economically
> significant nodes would reject their blocks? Perhaps they just wanted to
> enforce segwit?
> 
> These are all questions that have plausible answers, backed by evidence and
> argument. But because Bitcoin is a decentralized network no authority can tell
> you what the answers are.
> 
> -- 
> https://petertodd.org 'peter'[:-1]@petertodd.org
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