Re: [bitcoin-dev] Segwit2Mb - combined soft/hard fork - Request For Comments

From: Erik Aronesty <erik@q32•com>
To: "Jorge Timón" <jtimon@jtimon•cc>,
	"Bitcoin Protocol Discussion"
	<bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] Segwit2Mb - combined soft/hard fork - Request For Comments
Date: Fri, 2 Jun 2017 16:04:25 -0400	[thread overview]
Message-ID: <CAJowKg+aYUCgBu0nD9U63jm2SunGeqdqOwiMgnTSfE9JmNJAQw@mail.gmail.com> (raw)
In-Reply-To: <CABm2gDrAHo2P7t6SjituURqMUqs_=Lbp7X=g_j8nGoNKMKCRKQ@mail.gmail.com>

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From me to you ...this proposal doesn't lock in anything.   We could just
merge it with some small pushback - allow segwit to activate in Aug, then
"upgrade" the hard fork to be "spoonet in 18 months" instead.

On Sat, Apr 1, 2017 at 8:33 AM, Jorge Timón via bitcoin-dev <
bitcoin-dev@lists•linuxfoundation.org> wrote:

> Segwit replaces the 1 mb size limit with a weight limit of 4 mb. After
> segwit there's no need for MAX_BLOCK_BASE_SIZE anymore, let alone
> MAX_BLOCK2_BASE_SIZE.
> Thus, by "hf to 2 mb" it seems you just really mean hardforking from 4
> mb weight to 8 mb weight.
>
> I would also use the hardfork bit (sign bit in block.nNersion) as matt
> comments.
>
> > We're in a deadlock and it seems we can't go forward adding more
> functionality to segwit without the community approval (which include
> miners). This is obvious to me.Then we have to go back.
>
> If segwit is controversial the way it is (I still don't understand why
> despite having insistently asking to users and miners who claim to
> oppose it), adding more consensus rule changes won't make it any less
> controversial. If anything, it would be removing consensus rule
> changes, not adding them that could make it less controversial.
>
> By no means I want to dissuade you from working on this bip proposal,
> but I really don't see how it helps getting out of the deadlock at
> all.
>
>
> On Sat, Apr 1, 2017 at 1:44 PM, Sergio Demian Lerner via bitcoin-dev
> <bitcoin-dev@lists•linuxfoundation.org> wrote:
> > Some people have asked me for the current implementation of this patch to
> > review. I remind you that the current patch does not implement the
> hard-fork
> > signaling, as requested by Matt.
> >
> > The Segwit2Mb patch can be found here:
> > https://github.com/SergioDemianLerner/bitcoin/commits/master
> >
> > For now, the segwit2mb repo has a single test file using the old internal
> > blockchain building method (test/block_size_tests.cpp). This must be
> > replaced soon with a better external test using the bitcoin/qa/rpc-tests
> > tests, which I will begin to work on now after I collect all comments
> from
> > the community.
> >
> >
> > regards
> >
> >
> >
> > On Sat, Apr 1, 2017 at 3:55 AM, Jared Lee Richardson <jaredr26@gmail•com
> >
> > wrote:
> >>
> >> > Remember that the "hashpower required to secure bitcoin" is determined
> >> > as a percentage of total Bitcoins transacted on-chain in each block
> >>
> >> Can you explain this statement a little better?  What do you mean by
> >> that?  What does the total bitcoins transacted have to do with
> >> hashpower required?
> >>
> >>
> >> On Fri, Mar 31, 2017 at 2:22 PM, Matt Corallo via bitcoin-dev
> >> <bitcoin-dev@lists•linuxfoundation.org> wrote:
> >> > Hey Sergio,
> >> >
> >> > You appear to have ignored the last two years of Bitcoin hardfork
> >> > research and understanding, recycling instead BIP 102 from 2015. There
> >> > are many proposals which have pushed the state of hard fork research
> >> > much further since then, and you may wish to read some of the posts on
> >> > this mailing list listed at https://bitcoinhardforkresearch.
> github.io/
> >> > and make further edits based on what you learn. Your goal of "avoid
> >> > technical changes" appears to not have any basis outside of perceived
> >> > compromise for compromise sake, only making such a hardfork riskier
> >> > instead.
> >> >
> >> > At a minimum, in terms of pure technical changes, you should probably
> >> > consider (probably among others):
> >> >
> >> > a) Utilizing the "hard fork signaling bit" in the nVersion of the
> block.
> >> > b) Either limiting non-SegWit transactions in some way to fix the n**2
> >> > sighash and FindAndDelete runtime and memory usage issues or fix them
> by
> >> > utilizing the new sighash type which many wallets and projects have
> >> > already implemented for SegWit in the spending of non-SegWit outputs.
> >> > c) Your really should have replay protection in any HF. The clever fix
> >> > from
> >> > Spoonnet for poor scaling of optionally allowing non-SegWit outputs to
> >> > be spent with SegWit's sighash provides this all in one go.
> >> > d) You may wish to consider the possibility of tweaking the witness
> >> > discount and possibly discounting other parts of the input - SegWit
> went
> >> > a long ways towards making removal of elements from the UTXO set
> cheaper
> >> > than adding them, but didn't quite get there, you should probably
> finish
> >> > that job. This also provides additional tuneable parameters to allow
> you
> >> > to increase the block size while not having a blowup in the worst-case
> >> > block size.
> >> > e) Additional commitments at the top of the merkle root - both for
> >> > SegWit transactions and as additional space for merged mining and
> other
> >> > commitments which we may wish to add in the future, this should likely
> >> > be implemented an "additional header" ala Johnson Lau's Spoonnet
> >> > proposal.
> >> >
> >> > Additionally, I think your parameters here pose very significant risk
> to
> >> > the Bitcoin ecosystem broadly.
> >> >
> >> > a) Activating a hard fork with less than 18/24 months (and even
> then...)
> >> > from a fully-audited and supported release of full node software to
> >> > activation date poses significant risks to many large software
> projects
> >> > and users. I've repeatedly received feedback from various folks that a
> >> > year or more is likely required in any hard fork to limit this risk,
> and
> >> > limited pushback on that given the large increase which SegWit
> provides
> >> > itself buying a ton of time.
> >> >
> >> > b) Having a significant discontinuity in block size increase only
> serves
> >> > to confuse and mislead users and businesses, forcing them to rapidly
> >> > adapt to a Bitcoin which changed overnight both by hardforking, and by
> >> > fees changing suddenly. Instead, having the hard fork activate
> technical
> >> > changes, and then slowly increasing the block size over the following
> >> > several years keeps things nice and continuous and also keeps us from
> >> > having to revisit ye old blocksize debate again six months after
> >> > activation.
> >> >
> >> > c) You should likely consider the effect of the many technological
> >> > innovations coming down the pipe in the coming months. Technologies
> like
> >> > Lightning, TumbleBit, and even your own RootStock could significantly
> >> > reduce fee pressure as transactions move to much faster and more
> >> > featureful systems.
> >> >
> >> > Commitments to aggressive hard fork parameters now may leave miners
> >> > without much revenue as far out as the next halving (which current
> >> > transaction growth trends are indicating we'd just only barely reach
> 2MB
> >> > of transaction volume, let alone if you consider the effects of users
> >> > moving to systems which provide more features for Bitcoin
> transactions).
> >> > This could lead to a precipitous drop in hashrate as miners are no
> >> > longer sufficiently compensated.
> >> >
> >> > Remember that the "hashpower required to secure bitcoin" is determined
> >> > as a percentage of total Bitcoins transacted on-chain in each block,
> so
> >> > as subsidy goes down, miners need to be paid with fees, not just price
> >> > increases. Even if we were OK with hashpower going down compared to
> the
> >> > value it is securing, betting the security of Bitcoin on its price
> >> > rising exponentially to match decreasing subsidy does not strike me
> as a
> >> > particularly inspiring tradeoff.
> >> >
> >> > There aren't many great technical solutions to some of these issues,
> as
> >> > far as I'm aware, but it's something that needs to be incredibly
> >> > carefully considered before betting the continued security of Bitcoin
> on
> >> > exponential on-chain growth, something which we have historically
> never
> >> > seen.
> >> >
> >> > Matt
> >> >
> >> >
> >> > On March 31, 2017 5:09:18 PM EDT, Sergio Demian Lerner via bitcoin-dev
> >> > <bitcoin-dev@lists•linuxfoundation.org> wrote:
> >> >>Hi everyone,
> >> >>
> >> >>Segwit2Mb is the project to merge into Bitcoin a minimal patch that
> >> >>aims to
> >> >>untangle the current conflict between different political positions
> >> >>regarding segwit activation vs. an increase of the on-chain blockchain
> >> >>space through a standard block size increase. It is not a new
> solution,
> >> >>but
> >> >>it should be seen more as a least common denominator.
> >> >>
> >> >>Segwit2Mb combines segwit as it is today in Bitcoin 0.14+ with a 2MB
> >> >>block
> >> >>size hard-fork activated ONLY if segwit activates (95% of miners
> >> >>signaling), but at a fixed future date.
> >> >>
> >> >>The sole objective of this proposal is to re-unite the Bitcoin
> >> >>community
> >> >>and avoid a cryptocurrency split. Segwit2Mb does not aim to be best
> >> >>possible technical solution to solve Bitcoin technical limitations.
> >> >>However, this proposal does not imply a compromise to the future
> >> >>scalability or decentralization of Bitcoin, as a small increase in
> >> >>block
> >> >>size has been proven by several core and non-core developers not to
> >> >>affect
> >> >>Bitcoin value propositions.
> >> >>
> >> >>In the worst case, a 2X block size increase has much lower economic
> >> >>impact
> >> >>than the last bitcoin halving (<10%), which succeeded without problem.
> >> >>
> >> >>On the other side, Segwit2Mb primary goal is to be minimalistic: in
> >> >>this
> >> >>patch some choices have been made to reduce the number of lines
> >> >>modified in
> >> >>the current Bitcoin Core state (master branch), instead of
> implementing
> >> >>the
> >> >>most elegant solution. This is because I want to reduce the time it
> >> >>takes
> >> >>for core programmers and reviewers to check the correctness of the
> >> >>code,
> >> >>and to report and correct bugs.
> >> >>
> >> >>The patch was built by forking the master branch of Bitcoin Core,
> >> >>mixing a
> >> >>few lines of code from Jeff Garzik's BIP102,  and defining a second
> >> >>versionbits activation bit (bit 2) for the combined activation.
> >> >>
> >> >>The combined activation of segwit and 2Mb hard-fork nVersion bit is 2
> >> >>(DEPLOYMENT_SEGWIT_AND_2MB_BLOCKS).
> >> >>
> >> >>This means that segwit can still be activated without the 2MB
> hard-fork
> >> >>by
> >> >>signaling bit 1 in nVersion  (DEPLOYMENT_SEGWIT).
> >> >>
> >> >>The tentative lock-in and hard-fork dates are the following:
> >> >>
> >> >>Bit 2 signaling StartTime = 1493424000; // April 29th, 2017
> >> >>
> >> >>Bit 2 signaling Timeout = 1503964800; // August 29th, 2017
> >> >>
> >> >>HardForkTime = 1513209600; // Thu, 14 Dec 2017 00:00:00 GMT
> >> >>
> >> >>
> >> >>The hard-fork is conditional to 95% of the hashing power has approved
> >> >>the
> >> >>segwit2mb soft-fork and the segwit soft-fork has been activated (which
> >> >>should occur 2016 blocks after its lock-in time)
> >> >>
> >> >>For more information on how soft-forks are signaled and activated, see
> >> >>https://github.com/bitcoin/bips/blob/master/bip-0009.mediawiki
> >> >>
> >> >>This means that segwit would be activated before 2Mb: this is
> >> >>inevitable,
> >> >>as versionbits have been designed to have fixed activation periods and
> >> >>thresholds for all bits. Making segwit and 2Mb fork activate together
> >> >>at a
> >> >>delayed date would have required a major re-write of this code, which
> >> >>would
> >> >>contradict the premise of creating a minimalistic patch. However, once
> >> >>segwit is activated, the hard-fork is unavoidable.
> >> >>
> >> >>Although I have coded a first version of the segwit2mb patch (which
> >> >>modifies 120 lines of code, and adds 220 lines of testing code), I
> >> >>would
> >> >>prefer to wait to publish the source code until more comments have
> been
> >> >>received from the community.
> >> >>
> >> >>To prevent worsening block verification time because of the O(N^2)
> >> >>hashing
> >> >>problem, the simple restriction that transactions cannot be larger
> than
> >> >>1Mb
> >> >>has been kept. Therefore the worse-case of block verification time has
> >> >>only
> >> >>doubled.
> >> >>
> >> >>Regarding the hard-fork activation date, I want to give enough time to
> >> >>all
> >> >>active economic nodes to upgrade. As of Fri Mar 31 2017,
> >> >>https://bitnodes.21.co/nodes/ reports that 6332 out of 6955 nodes
> (91%)
> >> >>have upgraded to post 0.12 versions. Upgrade to post 0.12 versions can
> >> >>be
> >> >>used to identify economic active nodes, because in the 0.12 release
> >> >>dynamic
> >> >>fees were introduced, and currently no Bitcoin automatic payment
> system
> >> >>can
> >> >>operate without automatic discovery of the current fee rate. A
> pre-0.12
> >> >>would require constant manual intervention.
> >> >>Therefore I conclude that no more than 91% of the network nodes
> >> >>reported by
> >> >>bitnodes are active economic nodes.
> >> >>
> >> >>As Bitcoin Core 0.12 was released on February 2016, the time for this
> >> >>91%
> >> >>to upgrade has been around one year (under a moderate pressure of
> >> >>operational problems with unconfirmed transactions).
> >> >>Therefore we can expect a similar or lower time to upgrade for a
> >> >>hard-fork,
> >> >>after developers have discussed and approved the patch, and it has
> been
> >> >>reviewed and merged and 95% of the hashing power has signaled for it
> >> >>(the
> >> >>pressure not to upgrade being a complete halt of the operations).
> >> >>However I
> >> >>suggest that we discuss the hard-fork date and delay it if there is a
> >> >>real
> >> >>need to.
> >> >>
> >> >>Currently time works against the Bitcoin community, and so is delaying
> >> >>a
> >> >>compromise solution. Most of the community agree that halting the
> >> >>innovation for several years is a very bad option.
> >> >>
> >> >>After the comments collected by the community, a BIP will be written
> >> >>describing the resulting proposal details.
> >> >>
> >> >>If segwit2mb locks-in, before hard-fork occurs all bitcoin nodes
> should
> >> >>be
> >> >>updated to a Segwit2Mb enabled node to prevent them to be forked-away
> >> >>in a
> >> >>chain with almost no hashing-power.
> >> >>
> >> >>The proof of concept patch was made for Bitcoin Core but should be
> >> >>easily
> >> >>ported to other Bitcoin protocol implementations that already support
> >> >>versionbits. Lightweight (SPV) wallets should not be affected as they
> >> >>generally do not check the block size.
> >> >>
> >> >>I personally want to see the Lightning Network in action this year,
> use
> >> >>the
> >> >>non-malleability features in segwit, see the community discussing
> other
> >> >>exciting soft-forks in the scaling roadmap, Schnorr sigs, drivechains
> >> >>and
> >> >>MAST.
> >> >>
> >> >>I want to see miners, developers and industry side-by-side pushing
> >> >>Bitcoin
> >> >>forward, to increase the value of Bitcoin and prevent high transaction
> >> >>fees
> >> >>to put out of business use-cases that could have high positive social
> >> >>impact.
> >> >>
> >> >>I believe in the strength of a unified Bitcoin community. If you're a
> >> >>developer, please give your opinion, suggest changes, audit it, and
> >> >>take a
> >> >>stand with me to unlock the current Bitcoin deadlock.
> >> >>
> >> >>Contributions to the segwit2mb project are welcomed and awaited. The
> >> >>only
> >> >>limitation is to stick to the principle that the patch should be as
> >> >>simple
> >> >>to audit as possible. As an example, I wouldn't feel confident if the
> >> >>patch
> >> >>modified more than ~150 lines of code.
> >> >>
> >> >>Improvements unrelated to a 2 Mb increase or segwit, as beneficial as
> >> >>it
> >> >>may be to Bitcoin, should not be part of segwit2Mb.
> >> >>
> >> >>This proposal should not prevent other consensus proposals to be
> >> >>simultaneously merged: segwit2mb is a last resort solution in case we
> >> >>can
> >> >>not reach consensus on anything better.
> >> >>
> >> >>Again, the proposal is only a starting point: community feedback is
> >> >>expected and welcomed.
> >> >>
> >> >>Regards,
> >> >>Sergio Demian Lerner
> >> > _______________________________________________
> >> > bitcoin-dev mailing list
> >> > bitcoin-dev@lists•linuxfoundation.org
> >> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
> >
> >
> >
> > _______________________________________________
> > bitcoin-dev mailing list
> > bitcoin-dev@lists•linuxfoundation.org
> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
> >
> _______________________________________________
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