[bitcoin-dev] Yesterday's Taproot activation meeting on lockinontimeout (LOT)

Keagan McClelland keagan.mcclelland at gmail.com
Thu Feb 18 15:04:53 UTC 2021


Hi all,

I think it's important for us to consider what is actually being considered
for activation here.

The designation of "soft fork" is accurate but I don't think it adequately
conveys how non-intrusive a change like this is. All that taproot does
(unless I'm completely missing something) is imbue a previously undefined
script version with actual semantics. In order for a chain reorg to take
place it would mean that someone would have to have a use case for that
script version today. This is something I think that we can easily check by
digging through the UTXO set or history. If anyone is using that script
version, we absolutely should not be using it, but that doesn't mean that
we can't switch to a script version that no one is actually using.

If no one is even attempting to use the script version, then the change has
no effect on whether a chain split occurs because there is simply no block
that contains a transaction that only some of the network will accept.

Furthermore, I don't know how Bitcoin can stand the test of time if we
allow developers who rely on "undefined behavior" (which the taproot script
version presently is) to exert tremendous influence over what code does or
does not get run. This isn't a soft fork that makes some particular UTXO's
unspendable. It isn't one that bans miners from collecting fees. It is a
change that means that certain "always accept" transactions actually have
real conditions you have to meet. I can't imagine a less intrusive change.

On the other hand, choosing to let L=F be a somewhat final call sets a very
real precedent that 10% of what I estimate to be 1% of bitcoin users can
effectively block any change from here on forward. At that point we are
saying that miners are in control of network consensus in ways they have
not been up until now. I don't think this is a more desirable outcome to
let ~0.1% of the network get to block *non-intrusive* changes that the rest
of the network wants.

I can certainly live with an L=F attempt as a way to punt on the
discussion, maybe the activation happens and this will all be fine. But if
it doesn't, I hardly think that users of Bitcoin are just going to be like
"well, guess that's it for Taproot". I have no idea what ensues at that
point, but probably another community led UASF movement.

I wasn't super well educated on this stuff back in '17 when Segwit went
down, as I was new at that time, so if I'm missing something please say so.
But from my point of view, we can't treat all soft forks as equal.

Keagan

On Thu, Feb 18, 2021 at 7:43 AM Matt Corallo via bitcoin-dev <
bitcoin-dev at lists.linuxfoundation.org> wrote:

> We've had several softforks in Bitcoin which, through the course of their
> activation, had a several-block reorg. That
> should be indication enough that we need to very carefully consider
> activation to ensure we reduce the risk of that as
> much as absolutely possible. Again, while I think Taproot is a huge
> improvement and am looking forward to being able to
> use it, getting unlucky and hitting a 4-block reorg that happens to
> include a double-spend and some PR around an
> exchange losing millions would be worse than having Taproot is good.
>
> Matt
>
> On 2/18/21 09:26, Michael Folkson wrote:
> > Thanks for your response Matt. It is a fair challenge. There is always
> going to be an element of risk with soft forks,
> > all we can do is attempt to minimize that risk. I would argue that risk
> has been minimized for Taproot.
> >
> > You know (better than I do in fact) that Bitcoin (and layers built on
> top of it) greatly benefit from upgrades such as
> > Taproot. To say we shouldn't do Taproot or any future soft forks because
> there is a small but real risk of chain splits
> > I think is shortsighted. Indeed I think even if we collectively decided
> not to do any future soft fork upgrades ever
> > again on this mailing list that wouldn't stop soft fork attempts from
> other people in future.
> >
> > I don't think there is anything else we can do to minimize that risk for
> the Taproot soft fork at this point though I'm
> > open to ideas. To reiterate that risk will never be zero. I don't think
> I see Bitcoin as fragile as you seem to (though
> > admittedly you have a much better understanding than me of what happened
> in 2017).
> >
> > The likely scenario for the Taproot soft fork is LOT turns out to be
> entirely irrelevant and miners activate Taproot
> > before it becomes relevant. And even the unlikely worst case scenario
> would only cause short term disruption and
> > wouldn't kill Bitcoin long term.
> >
> > On Thu, Feb 18, 2021 at 2:01 PM Matt Corallo <lf-lists at mattcorallo.com
> <mailto:lf-lists at mattcorallo.com>> wrote:
> >
> >     If the eventual outcome is that different implementations (that have
> material *transaction processing* userbases,
> >     and I’m not sure to what extent that’s true with Knots) ship
> different consensus rules, we should stop here and not
> >     activate Taproot. Seriously.
> >
> >     Bitcoin is a consensus system. The absolute worst outcome at all
> possible is to have it fall out of consensus.
> >
> >     Matt
> >
> >>     On Feb 18, 2021, at 08:11, Michael Folkson via bitcoin-dev <
> bitcoin-dev at lists.linuxfoundation.org
> >>     <mailto:bitcoin-dev at lists.linuxfoundation.org>> wrote:
> >>
> >>     
> >>     Right, that is one option. Personally I would prefer a Bitcoin Core
> release sets LOT=false (based on what I have
> >>     heard from Bitcoin Core contributors) and a community effort
> releases a version with LOT=true. I don't think users
> >>     should be forced to choose something they may have no context on
> before they are allowed to use Bitcoin Core.
> >>
> >>     My current understanding is that roasbeef is planning to set
> LOT=false on btcd (an alternative protocol
> >>     implementation to Bitcoin Core) and Luke Dashjr hasn't yet decided
> on Bitcoin Knots.
> >>
> >>
> >>
> >>     On Thu, Feb 18, 2021 at 11:52 AM ZmnSCPxj <ZmnSCPxj at protonmail.com
> <mailto:ZmnSCPxj at protonmail.com>> wrote:
> >>
> >>         Good morning all,
> >>
> >>         > "An activation mechanism is a consensus change like any other
> change, can be contentious like any other
> >>         change, and we must resolve it like any other change. Otherwise
> we risk arriving at the darkest timeline."
> >>         >
> >>         > Who's we here?
> >>         >
> >>         > Release both and let the network decide.
> >>
> >>         A thing that could be done, without mandating either LOT=true
> or LOT=false, would be to have a release that
> >>         requires a `taprootlot=1` or `taprootlot=0` and refuses to
> start if the parameter is not set.
> >>
> >>         This assures everyone that neither choice is being forced on
> users, and instead what is being forced on users,
> >>         is for users to make that choice themselves.
> >>
> >>         Regards,
> >>         ZmnSCPxj
> >>
> >>         >
> >>         > On Thu, Feb 18, 2021 at 3:08 AM Michael Folkson via
> bitcoin-dev <bitcoin-dev at lists.linuxfoundation.org
> >>         <mailto:bitcoin-dev at lists.linuxfoundation.org>> wrote:
> >>         >
> >>         > > Thanks for your response Ariel. It would be useful if you
> responded to specific points I have made in the
> >>         mailing list post or at least quote these ephemeral "people"
> you speak of. I don't know if you're responding
> >>         to conversation on the IRC channel or on social media etc.
> >>         > >
> >>         > > > The argument comes from a naive assumption that users
> MUST upgrade to the choice that is submitted into
> >>         code. But in fact this isn't true and some voices in this
> discussion need to be more humble about what users
> >>         must or must not run.
> >>         > >
> >>         > > I personally have never made this assumption. Of course
> users aren't forced to run any particular software
> >>         version, quite the opposite. Defaults set in software versions
> matter though as many users won't change them.
> >>         > >
> >>         > > > Does no one realize that it is a very possible outcome
> that if LOT=true is released there may be only a
> >>         handful of people that begin running it while everyone else
> delays their upgrade (with the very good reason of
> >>         not getting involved in politics) and a year later those
> handful of people just become stuck at the moment of
> >>         MUST_SIGNAL, unable to mine new blocks?
> >>         > >
> >>         > > It is a possible outcome but the likely outcome is that
> miners activate Taproot before LOT is even
> >>         relevant. I think it is prudent to prepare for the unlikely but
> possible outcome that miners fail to activate
> >>         and hence have this discussion now rather than be unprepared
> for that eventuality. If LOT is set to false in a
> >>         software release there is the possibility (T2 in
> >>
> https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-February/018380.html
> >>         <
> https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-February/018380.html>)
> of individuals or a
> >>         proportion of the community changing LOT to true. In that sense
> setting LOT=false in a software release
> >>         appears to be no more safe than LOT=true.
> >>         > >
> >>         > > > The result: a wasted year of waiting and a minority of
> people who didn't want to be lenient with miners
> >>         by default.
> >>         > >
> >>         > > There is the (unlikely but possible) possibility of a
> wasted year if LOT is set to false and miners fail
> >>         to activate. I'm not convinced by this perception that LOT=true
> is antagonistic to miners. I actually think it
> >>         offers them clarity on what will happen over a year time period
> and removes the need for coordinated or
> >>         uncoordinated community UASF efforts on top of LOT=false.
> >>         > >
> >>         > > > An activation mechanism is a consensus change like any
> other change, can be contentious like any other
> >>         change, and we must resolve it like any other change. Otherwise
> we risk arriving at the darkest timeline.
> >>         > >
> >>         > > I don't know what you are recommending here to avoid "this
> darkest timeline". Open discussions have
> >>         occurred and are continuing and in my mailing list post that
> you responded to **I recommended we propose
> >>         LOT=false be set in protocol implementations such as Bitcoin
> Core**. I do think this apocalyptic language
> >>         isn't particularly helpful. In an open consensus system
> discussion is healthy, we should prepare for bad or
> >>         worst case scenarios in advance and doing so is not
> antagonistic or destructive. Mining pools have pledged
> >>         support for Taproot but we don't build secure systems based on
> pledges of support, we build them to minimize
> >>         trust in any human actors. We can be grateful that people like
> Alejandro have worked hard on
> >>         taprootactivation.com <http://taprootactivation.com> (and this
> effort has informed the discussion) without
> >>         taking pledges of support as cast iron guarantees.
> >>         > >
> >>         > > TL;DR It sounds like you agree with my recommendation to
> set LOT=false in protocol implementations in my
> >>         email :)
> >>         > >
> >>         > > On Thu, Feb 18, 2021 at 5:43 AM Ariel Lorenzo-Luaces <
> arielluaces at gmail.com
> >>         <mailto:arielluaces at gmail.com>> wrote:
> >>         > >
> >>         > > > Something what strikes me about the conversation is the
> emotion surrounding the letters UASF.
> >>         > > > It appears as if people discuss UASF as if it's a massive
> tidal wave of support that is inevitable, like
> >>         we saw during segwit activation. But the actual definition is
> "any activation that is not a MASF".
> >>         > > > A UASF can consist of a single node, ten nodes, a
> thousand, half of all nodes, all business' nodes, or
> >>         even all the non mining nodes. On another dimension it can have
> zero mining support, 51% support, 49% support,
> >>         or any support right up against a miner activation threshold.
> >>         > > > Hell a UASF doesn't even need code or even a single node
> running as long as it exists as a possibility
> >>         in people's minds.
> >>         > > > The only thing a UASF doesn't have is miner support above
> an agreed activation threshold (some number
> >>         above %51).
> >>         > > > I say this because it strikes me when people say that
> they are for LOT=true with the logic that since a
> >>         UASF is guaranteed to happen then it's better to just make it
> default from the beginning. Words like
> >>         coordination and safety are sometimes sprinkled into the
> argument.
> >>         > > > The argument comes from a naive assumption that users
> MUST upgrade to the choice that is submitted into
> >>         code. But in fact this isn't true and some voices in this
> discussion need to be more humble about what users
> >>         must or must not run.
> >>         > > > Does no one realize that it is a very possible outcome
> that if LOT=true is released there may be only a
> >>         handful of people that begin running it while everyone else
> delays their upgrade (with the very good reason of
> >>         not getting involved in politics) and a year later those
> handful of people just become stuck at the moment of
> >>         MUST_SIGNAL, unable to mine new blocks? Or attracting a
> minority of miners, activating, and forking off into a
> >>         minority fork. Then a lot=false could be started that ends up
> activating the feature now that the stubborn
> >>         option has ran its course.
> >>         > > > The result: a wasted year of waiting and a minority of
> people who didn't want to be lenient with miners
> >>         by default. The chains could be called BitcoinLenient and
> BitcoinStubborn.
> >>         > > > How is that strictly safer or more coordinated?
> >>         > > > I may be in the minority, or maybe a silent majority, or
> maybe a majority that just hasn't considered
> >>         this as a choice but honestly if there is contention about
> whether we're going to be stubborn or lenient with
> >>         miners for Taproot and in the future then I prefer to just not
> activate anything at all. I'm fine for calling
> >>         bitcoin ossified, accepting that segwit is Bitcoin's last
> network upgrade. Taproot is amazing but no new
> >>         feature is worth a network split down the middle.
> >>         > > > Maybe in 10 or 20 years, when other blockchains implement
> features like Taproot and many more, we will
> >>         become envious enough to put aside our differences on how to
> behave towards miners and finally activate Taproot.
> >>         > > > An activation mechanism is a consensus change like any
> other change, can be contentious like any other
> >>         change, and we must resolve it like any other change. Otherwise
> we risk arriving at the darkest timeline.
> >>         > > > Cheers
> >>         > > > Ariel Lorenzo-Luaces
> >>         > > > On Feb 17, 2021, at 7:05 AM, Michael Folkson via
> bitcoin-dev <bitcoin-dev at lists.linuxfoundation.org
> >>         <mailto:bitcoin-dev at lists.linuxfoundation.org>> wrote:
> >>         > > >
> >>         > > > > Yesterday (February 16th) we held a second meeting on
> Taproot
> >>         > > > > activation on IRC which again was open to all. Despite
> what appeared
> >>         > > > > to be majority support for LOT=false over LOT=true in
> the first
> >>         > > > > meeting I (and others) thought the arguments had not
> been explored in
> >>         > > > > depth and that we should have a follow up meeting
> almost entirely
> >>         > > > > focused on whether LOT (lockinontimeout) should be set
> to true or
> >>         > > > > false.
> >>         > > > >
> >>         > > > > The meeting was announced here:
> >>         > > > >
> https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-February/018380.html
> >>         <
> https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-February/018380.html
> >
> >>         > > > >
> >>         > > > > In that mailing list post I outlined the arguments for
> LOT=true (T1 to
> >>         > > > > T6) and arguments for LOT=false (F1 to F6) in their
> strongest form I
> >>         > > > > could. David Harding responded with an additional
> argument for
> >>         > > > > LOT=false (F7) here:
> >>         > > > >
> https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-February/018415.html
> >>         <
> https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-February/018415.html
> >
> >>         > > > >
> >>         > > > > These meetings are very challenging given they are open
> to all, you
> >>         > > > > don’t know who will attend and you don’t know most
> people’s views in
> >>         > > > > advance. I tried to give time for both the LOT=true
> arguments and the
> >>         > > > > LOT=false arguments to be discussed as I knew there was
> support for
> >>         > > > > both. We only tried evaluating which had more support
> and which had
> >>         > > > > more strong opposition towards the end of the meeting.
> >>         > > > >
> >>         > > > > The conversation log is here:
> >>         > > > > http://gnusha.org/taproot-activation/2021-02-16.log <
> http://gnusha.org/taproot-activation/2021-02-16.log>
> >>         > > > >
> >>         > > > > (If you are so inclined you can watch a video of the
> meeting here.
> >>         > > > > Thanks to the YouTube account “Bitcoin” for setting up
> the livestream:
> >>         > > > > https://www.youtube.com/watch?v=vpl5q1ovMLM <
> https://www.youtube.com/watch?v=vpl5q1ovMLM>)
> >>         > > > >
> >>         > > > > A summary of the meeting was provided by Luke Dashjr on
> Mastodon here:
> >>         > > > >
> https://bitcoinhackers.org/@lukedashjr/105742918779234566
> >>         <https://bitcoinhackers.org/@lukedashjr/105742918779234566>
> >>         > > > >
> >>         > > > > Today's #Bitcoin #Taproot meeting was IMO largely
> unproductive, but we
> >>         > > > > did manage to come to consensus on everything but
> LockinOnTimeout.
> >>         > > > >
> >>         > > > > Activation height range: 693504-745920
> >>         > > > >
> >>         > > > > MASF threshold: 1815/2016 blocks (90%)
> >>         > > > >
> >>         > > > > Keep in mind only ~100 people showed for the meetings,
> hardly
> >>         > > > > representative of the entire community.
> >>         > > > >
> >>         > > > > So, these details remain JUST a proposal for now.
> >>         > > > >
> >>         > > > > It seems inevitable that there won't be consensus on
> LOT.
> >>         > > > >
> >>         > > > > Everyone will have to choose for himself. :/
> >>         > > > >
> >>         > > > > Personally I agree with most of this. I agree that
> there wasn’t
> >>         > > > > overwhelming consensus for either LOT=true or
> LOT=false. However, from
> >>         > > > > my perspective there was clearly more strong opposition
> (what would
> >>         > > > > usually be deemed a NACK in Bitcoin Core review
> terminology) from
> >>         > > > > Bitcoin Core contributors, Lightning developers and
> other community
> >>         > > > > members against LOT=true than there was for LOT=false.
> Andrew Chow
> >>         > > > > tried to summarize views from the meeting in this
> analysis:
> >>         > > > >
> https://gist.github.com/achow101/3e179501290abb7049de198d46894c7c
> >>         <
> https://gist.github.com/achow101/3e179501290abb7049de198d46894c7c>
> >>         > > > >
> >>         > > > > I am also aware of other current and previous Bitcoin
> Core
> >>         > > > > contributors and Lightning developers who didn’t attend
> the meeting in
> >>         > > > > person who are opposed to LOT=true. I don’t want to put
> them in the
> >>         > > > > spotlight for no reason but if you go through the
> conversation logs of
> >>         > > > > not only the meeting but the weeks of discussion prior
> to this meeting
> >>         > > > > you will see their views evaluated on the
> ##taproot-activation
> >>         > > > > channel. In addition, on taprootactivation.com <
> http://taprootactivation.com> some mining pools
> >>         > > > > expressed a preference for lot=false though I don’t
> know how strong
> >>         > > > > that preference was.
> >>         > > > >
> >>         > > > > I am only one voice but it is my current assessment
> that if we are to
> >>         > > > > attempt to finalize Taproot activation parameters and
> propose them to
> >>         > > > > the community at this time our only option is to
> propose LOT=false.
> >>         > > > > Any further delay appears to me counterproductive in
> our collective
> >>         > > > > aim to get the Taproot soft fork activated as early as
> possible.
> >>         > > > >
> >>         > > > > Obviously others are free to disagree with that
> assessment and
> >>         > > > > continue discussions but personally I will be
> attempting to avoid
> >>         > > > > those discussions unless prominent new information
> comes to light or
> >>         > > > > various specific individuals change their minds.
> >>         > > > >
> >>         > > > > Next week we are planning a code review of the Bitcoin
> Core PR #19573
> >>         > > > > which was initially delayed because of this LOT
> discussion. As I’ve
> >>         > > > > said previously that will be loosely following the
> format of the
> >>         > > > > Bitcoin Core PR review club and will be lower level and
> more
> >>         > > > > technical. That is planned for Tuesday February 23rd at
> 19:00 UTC on
> >>         > > > > the IRC channel ##taproot-activation.
> >>         > > > >
> >>         > > > > Thanks to the meeting participants (and those who
> joined the
> >>         > > > > discussion on the channel prior and post the meeting)
> for engaging
> >>         > > > > productively and in good faith.
> >>         > >
> >>         > > --
> >>         > > Michael Folkson
> >>         > > Email: michaelfolkson at gmail.com <mailto:
> michaelfolkson at gmail.com>
> >>         > > Keybase: michaelfolkson
> >>         > > PGP: 43ED C999 9F85 1D40 EAF4 9835 92D6 0159 214C FEE3
> >>         > > _______________________________________________
> >>         > > bitcoin-dev mailing list
> >>         > > bitcoin-dev at lists.linuxfoundation.org <mailto:
> bitcoin-dev at lists.linuxfoundation.org>
> >>         > >
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
> >>         <https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
> >
> >>
> >>
> >>
> >>
> >>     --
> >>     Michael Folkson
> >>     Email: michaelfolkson at gmail.com <mailto:michaelfolkson at gmail.com>
> >>     Keybase: michaelfolkson
> >>     PGP: 43ED C999 9F85 1D40 EAF4 9835 92D6 0159 214C FEE3
> >>     _______________________________________________
> >>     bitcoin-dev mailing list
> >>     bitcoin-dev at lists.linuxfoundation.org <mailto:
> bitcoin-dev at lists.linuxfoundation.org>
> >>     https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
> >>     <https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev>
> >
> >
> >
> > --
> > Michael Folkson
> > Email: michaelfolkson at gmail.com <mailto:michaelfolkson at gmail.com>
> > Keybase: michaelfolkson
> > PGP: 43ED C999 9F85 1D40 EAF4 9835 92D6 0159 214C FEE3
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
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>
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