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

[Sergio Demian Lerner <sergio.d.lerner@gmail.com>]

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By "upgrade"  the HF you mean activate 2X and then spoonet 18 months later
or do not activate the 2x HF at all?





On Fri, Jun 2, 2017 at 4:04 PM, Erik Aronesty via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> 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://bitcoinhardforkresearc
>> h.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
>> >
>> >
>> >
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>> >
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