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

Eric Voskuil eric at voskuil.org
Fri Aug 16 17:44:47 UTC 2019

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.


> On Aug 16, 2019, at 12:06, Peter Todd via bitcoin-dev <bitcoin-dev at 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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