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

Sat Jun 3 00:53:55 UTC 2017

What I mean is that spoonet and other HF improvements, and a slower
timeline needs to be folded in ...before the HF activation date - to make
it far more likely that the community adopts the whole proposal and the
chain doesn't fragment.

If you try to push a 2mb with no safety checks and nothing else improved -
nothing will happen.

Take a quick look at the COOP proposal...it gets us to 4mb blocks in 4
years....gradually, no massive fee swings.

On Fri, Jun 2, 2017 at 5:51 PM, Sergio Demian Lerner <
sergio.d.lerner at gmail.com> wrote:

> 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 at 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 at 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 at 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 at 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 at 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 at 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 at lists.linuxfoundation.org
>>> >> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>>> >
>>> >
>>> >
>>> > _______________________________________________
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>>> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>>> >
>>> _______________________________________________
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>>
>>
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