[bitcoin-dev] Towards a means of measuring user support for Soft Forks

[Keagan McClelland]

Hi all,

Alongside the debate with CTV right now there's a second debate that was
not fully hashed out in the activation of Taproot. There is a lot of
argument around what Speedy Trial is or isn't, what BIP8 T/F is or isn't
etc. A significant reason for the breakdown in civility around this debate
is that because we don't have a means of measuring user support for
proposed sof-fork changes, it invariably devolves into people claiming that
their circles support/reject a proposal, AND that their circles are more
broadly representative of the set of Bitcoin users as a whole.

It seems everyone in this forum has at one point or another said "I would
support activation of ____ if there was consensus on it, but there isn't".
This statement, in order to be true, requires that there exist a set of
conditions that would convince you that there is consensus. People have
tried to dodge this question by saying "it's obvious", but the reality is
that it fundamentally isn't. My bubble has a different "obvious" answer
than any of yours.

Secondly, due to the trauma of the block size wars, no one wants to utter a
statement that could imply that miners have any influence over what
rulesets get activated or don't. As such "miner signaling" is consistently
devalued as a signal for market demand. I don't think this is reasonable
since following the events of '17  miners are aware that they have the
strong incentive that they understand market demand. Nevertheless, as it
stands right now the only signal we have to work with is miner signaling,
which I think is rightly frustrating to a lot of people.

So how can we measure User Support for a proposed rule change?

I've had this idea floating around in the back of my head for a while, and
I'd like to solicit some feedback here. Currently, all forms of activation
that are under consideration involve miner signaling in one form or
another. What if we could make it such that users could more directly
pressure miners to act on their behalf? After all, if miners are but the
humble servants of user demands, this should be in alignment with how
people want Bitcoin to behave.

Currently, the only means users have of influencing miner decisions are A.
rejection of blocks that don't follow rules and B. paying fees for
transaction inclusion. I suggest we combine these in such a way that
transactions themselves can signal for upgrade. I believe (though am not
certain) that there are "free" bits in the version field of a transaction
that are presently ignored. If we could devise a mapping between some of
those free bits, and the signaling bits in the block header, it would be
possible to have rules as follows:

- A transaction signaling in the affirmative MUST NOT be included in a
block that does not signal in the affirmative
- A transaction that is NOT signaling MAY be included in a block regardless
of that block's signaling vector
- (Optional) A transaction signaling in the negative MUST NOT be included
in a block that signals in the affirmative

Under this set of conditions, a user has the means of sybil-resistant
influence over miner decisions. If a miner cannot collect the fees for a
transaction without signaling, the user's fee becomes active economic
pressure for the miner to signal (or not, if we include some variant of the
negative clause). In this environment, miners could have a better view into
what users do want, as would the Bitcoin network at large.

Some may take issue with the idea that people can pay for the outcome they
want and may try to compare a method like this to Proof of Stake, but there
are only 3 sybil resistant mechanisms I am aware of, and any "real" view
into what social consensus looks like MUST be sybil resistant:

- Hashpower
- Proof of personhood (KYC)
- Capital burn/risk

Letting hashpower decide this is the thing that is currently contentious,
KYC is dead on arrival both on technical and social grounds, which really
just leaves some means of getting capital into the process of consensus
measurement. This mechanism I'm proposing is measurable completely
en-protocol and doesn't require trust in institutions that fork futures
would. Additionally it could be an auxiliary feature of the soft fork
deployment scheme chosen making it something you could neatly package all
together with the deployment itself.

There are many potential tweaks to the design I propose above:
1. Do we include a notion of negative signaling (allowing for the
possibility of rejection)
2. Do we make it such that miner signaling must be congruent with >X% of
transactions, where congruence is that the signal must match any
non-neutral signal of transaction.

Some anticipated objections:

1. signaling isn't voting, no deployment should be made without consensus
first.
- yeah well we can't currently measure consensus right now, so that's not a
super helpful thing to say and is breeding ground for abuse in the form of
certain people making the unsubstantiated claim that consensus does or does
not exist for a particular initiative

2. This is just a proposal for "pay to play", we should not let the wealthy
make consensus decisions.
- I agree that wealth should not be able to strong-arm decision making. But
the status quo seems even worse where we let publicly influential people
decide consensus in such a way where not only do they not "lose ammunition"
in the process of campaigning, but actually accrue it, creating really bad
long-term balances of power.

3. Enforcing this proposal requires its own soft fork.
- Yes. It does...and there's a certain cosmic irony to that, but before we
consider how to make this happen, I'd like to even discuss whether or not
it's a good idea.

4. This gives CoinJoin pool operators and L2 protocol implementations power
over deciding consensus.
- I see this as an improvement over the status quo

5. This encourages "spam"
- If you pay the fees, it's not spam.

The biggest question I'd like to pose to the forum is:
- Does a scheme like this afford us a better view into consensus than we
have today?
- Can it be gamed to give us a *worse* view into consensus? How?
- Does it measure the right thing? If not, what do you think is the right
thing to measure? (assuming we could)
- Should I write a BIP spec'ing this out in detail?

Cheers,
Keagan
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