Re: [bitcoin-dev] Making the case for flag day activation of taproot

["Russell O'Connor" <roconnor@blockstream.com>]

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While I support essentially any proposed taproot activation method,
including a flag day activation, I think it is premature to call BIP8 dead.

Even today, I still think that starting with BIP8 LOT=false is, generally
speaking, considered a reasonably safe activation method in the sense that
I think it will be widely considered as a "not wholly unacceptable"
approach to activation.

After a normal and successful Core update with LOT=false, we will have more
data showing broad community support for the taproot upgrade in hand.  In
the next release, 6 months later or so, Core could then confidently deploy
a BIP8 LOT=true client, should it prove to be necessary.  A second Core
deployment of LOT=true would mitigate some of the concerns with LOT=false,
but still provide a period beforehand to objective actions taken by the
community in support of taproot.  We don't even have to have agreement
today on a second deployment of LOT=true after 6 months to start the
process of a LOT=false deployment. The later deployment will almost
certainly be moot, and we will have 6 months to spend debating the LOT=true
deployment versus doing a flag day activation or something else.

I don't think we need to start self-sabotaging our efforts to get taproot
activated this year just yet.  Let's cherry-pick the commits of PR #19573
to split it up into non-MUST_SIGNAL and MUST_SIGNAL components, and get
some reviews on that first.  Then afterwards we can decide if BIP8 is dead
or not.

On Wed, Mar 3, 2021 at 9:39 AM Chris Belcher via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> The bitcoin world is close to total gridlock on the question of how to
> activate taproot. There's no agreement on activation[1][2], and if an
> agreement isn't reached then nothing happens. That would be really
> terrible because we'd miss out on the benefits of taproot and
> potentially other future soft forks.
>
> A major problem with BIP8 is that it would result to a situation where
> different parts of the bitcoin ecosystem run different consensus rules.
> Some people will run LOT=true and others LOT=false. Worst of all, it
> becomes vulnerable to a twitter/reddit/social media blitz which could
> attempt to move the date of miner activation around.
>
> Twitter and reddit drama provide a perfect cover for social attacks on
> bitcoin.
>
> Forced signalling leads to brinksmanship. Where two or more sides
> (backed up by social media drama) enter into a game of chicken with
> deployed nodes. If one of them doesn't concede then we get a damaging
> chain split. And the $1 trillion in value that the bitcoin network
> protects is put at risk. From the point of view of a miner or big
> exchange stuck in the middle, if they look at the ecosystem of twitter
> and reddit (especially if you think about all the problems with bots and
> sockpuppets) they have no idea which consensus rules they should
> actually follow and exactly what date they take effect. Miners,
> exchanges, merchants and the rest of the ecosystem exist to serve their
> customers and users, and trouble happens when they don't know what their
> customers really want. Social media attacks are not just a theoretical
> concern; back during the block size drama, the bitcoin reddits were
> targetted by bots, sockpuppets and brigading[3].
>
> Enter flag day activation. With a flag day there can be no
> brinksmanship. A social media blitz cant do anything except have its own
> followers fork away. Crucially, miner signalling cant be used to change
> the activation date for nodes that didn't choose to and just passively
> follow signalling. Changing the activation date requires all those users
> to actually run different node software.
>
> Flag day activation works simply: we choose a block height and after
> that block height the new taproot rules become enforced.
>
>
> Supporters of the permissionless, "users rule" approach of LOT=true
> should be happy because it completely takes miners out of activation.
>
> Supporters of the safe, conservative approach of LOT=false can be made
> happy with a few ways of derisking:
>
> * Getting mining pools, businesses and users to look at the code and ask
> if they (a) think its either neutral or good for their business or use
> case and (b) they believe others view it similarly and that the
> consensus changes proposed have a good social consensus around them.
>
> * Setting the flag day far in the future (18 months or 2 years in the
> original proposal[3]).
>
>
> == What if flag day activation is used maliciously? ==
>
> What if one day the Core developer team is co-opted and uses the flag
> day method to do something bad? For example, a soft fork where sending
> to certain blacklisted addresses is not allowed. The bitcoin user
> community who wants to resist this can create their own
> counter-soft-fork full node, where the first block after the flag day
> MUST pay to one of those addresses on the blacklist. This forces a chain
> split between the censorship rules and the no-censorship rules, and its
> pretty obvious that the real bitcoin which most people follow will be
> the chain without censorship.
>
> For example, if a group of users didn't agree with taproot then they
> could create their own counter-flag-day-activation which requires that a
> transaction is included that does an invalid-spend from a taproot output
> in the first block after the flag day height.
>
> This is always possible with any user activated soft fork. In BIP8
> LOT=true it could be done by rejecting block headers with certain
> version bits signalled.
>
>
> == But it will take so long! ==
>
> We seem to be at a deadlock now. This will take less time than any other
> method, because other methods might never happen. BIP8 is dead and from
> what I see there's no other credible plan.
>
> We've already waited years for taproot. I remember listening to talks
> about bitcoin from 2015 of people discussing Schnorr signatures. And
> given how slow segwit and p2sh adoption were its pretty likely that
> we'll waiting a while for taproot to be actually adopted.
>
>
> == A social media blitz could still try to activate it early ==
>
> The brinksmanship only works because miner signalling can make many
> other nodes activate early, even if those other nodes didn't do
> anything. There can't be a game of chicken that puts the bitcoin network
> at risk.
>
> If a group of people did adopt alternative node software which has a
> shorter flag day, they actually have a risk of slow blocks. Because they
> cant trick or force any other nodes to come along with them, they are
> likely to only have a small economy and therefore would lose a lot of
> hashrate. Imagine trading bitcoins for cash in person and instead of
> waiting 10 minutes for a confirmation you have to wait 3 hours because
> the blocks are slow.
>
> Also, the argument for downloading and running a different software only
> to speed up activation is pretty weak. Taproot would activate in ~18
> months, so why are you so impatient that you need it in 6 months? And
> risk slow blocks for you while doing so? The big difference with BIP148
> the segwit UASF, is that people *had to* run some other software
> otherwise they would get *no soft fork at all*.
>
>
> == Without miner signalling how do we know the new rules are even
> activated? ==
>
> When did you see miners signalling their support for the inflation
> schedule?
>
> Bitcoin's rules are enforced by wallets backed by full nodes. You'll
> always know if your own full node is enforcing the new rules. The thing
> that matters isnt miner signalling but your own full node, and the nodes
> of those you trade with.
>
> Flag day activation is quite similar to the way block reward halvenings
> work. At and after block height 630000 miners are only allowed to create
> 6.25 BTC rather than 12.5 BTC. Everyone knows that if miners continued
> to create 12.5 BTC or more they would be unable to sell or spend those
> coins anywhere.
>
> In 2017 when segwit was being activated people created a huge list of
> various bitcoin companies, merchants and wallets:
>
> https://web.archive.org/web/20171228111943/https://bitcoincore.org/en/segwit_adoption/
> Looking at that list, you would know that if someone stole coins from a
> segwit address they would be unable to deposit them in many exchanges
> and merchants: Bitrefill, Bitstamp, Kraken, Localbitcoins, Paxful,
> Vaultoro, HitBTC, etc.
>
> Then what happened is only a month after S2X was beaten this guy moved
> 40000 BTC to a segwit address, confident about the power of the network
> to protect his coins.
>
> https://old.reddit.com/r/Bitcoin/comments/7tcmi4/bitcointalks_famous_user_loaded_moved_his_40k_btc/
>
> If there's ever any doubt about flag day activation we can always draw
> up a similar list, although if there's broad consensus about it then
> there's no reason why bitcoin businesses wouldn't upgrade to the latest
> Core, like they did with every other previous soft fork.
>
>
> == This gives the impression that Core developers control the protocol ==
>
> This objection has a mirror image argument: BIP8 with LOT=false gives
> the impression that miners control the protocol(!)
>
> Eventually some group has to make a decision. We will ask the bitcoin
> economy and users what they think of flag day activation. It's pretty
> clear that nobody seriously objects to taproot, and as described above
> if Core developers did something evil the community could resist it with
> a counter-flag-day-activation.
>
>
>
> == TL;DR ==
>
> I believe flag day activation is the way forward. It should answer all
> the objections and risks which make other methods too controversial.
> Let's go ahead and bring taproot to bitcoin!
>
>
>
> == References ==
>
> [1] -
>
> https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-February/018498.html
>       luke-jr posts saying LOT=false in his view reintroduces a bug, he
> compares it to introducing an inflation bug and just hoping that miners
> will not exploit it.
>
> [2] -
>
> https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-February/018425.html
>       This whole thread has many people disagreeing with LOT=true
>
> [3] -
>
> https://old.reddit.com/r/Bitcoin/comments/4biob5/research_into_instantaneous_vote_behavior_in/
>
>
> https://old.reddit.com/r/Bitcoin/comments/3v04pd/can_we_please_have_a_civil_discussion_about/cxjnz1d/?context=1
>
>
> https://old.reddit.com/r/Bitcoin/comments/41ykkt/members_trying_to_destroy_bitcoin_on_this_thread/cz6ccka/?context=3
>
> [4] -
>
> https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-February/018495.html
>       Matt Corallo's flag day activation proposal
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