Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 3BD069C for ; Fri, 2 Jun 2017 20:04:29 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-qt0-f182.google.com (mail-qt0-f182.google.com [209.85.216.182]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id E70E118F for ; Fri, 2 Jun 2017 20:04:26 +0000 (UTC) Received: by mail-qt0-f182.google.com with SMTP id w1so40181399qtg.2 for ; Fri, 02 Jun 2017 13:04:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:sender:in-reply-to:references:from:date:message-id :subject:to; bh=ImogCVZ35DKetv7kAdzVCh5QcAbFWR2Dp7eNeVxyrDo=; b=gJqgK4DxFzzcX64QrmaUR1rkeCkcjSrNqpXXPdffSGb449e2zykVhBIWe66ROewy+g PQ1M8hfttLOqzhuxEizE6Hjvs+rz8Pn22qC7iWvmuE9GrAv75Xg1t83PVgxtFJ+6M7w3 U2CbBtM/S9XzAXmcUG86QRVR+tB/Evp2/qMTOBMdJkCqa/ckjSLnF1XTBqys5wXU8Q/+ Y8xcK511eIQeiPcxYoP6EgwJEbKXflhvpSO0vRVvt55u2smltLssMhEkldTrzPWCe7Vy YS8xrNFv9XhTQSl6Uh/ckkFpP5Z3ONGxF3SDfX3T/MkDP5v5/putsAyzkIVIQrAaCNP+ 6mnw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:sender:in-reply-to:references:from :date:message-id:subject:to; bh=ImogCVZ35DKetv7kAdzVCh5QcAbFWR2Dp7eNeVxyrDo=; b=VE9OfDegds2P7aisyRJx+8XuRbjY+0Z4k7+yZE+9LTtWROycW7zgE8iCuOvArwBbye A7h2gpArd3bmhvR/214rwfEqtzU/K2pPiNTxhR8qyRkodIMnW3xr1UcdI64PWTj+gYG7 i1ZxfdiO0OC/1QyQUdwdiJ+YuRGF4Z0aNu6pbVuskKdQF2/vyLPhK3lLmGkuk9TwuMqc VeR/ibS19G7WytOYhhNjg3fiR4z3uovXXJ73X9jtxfqnsQGR/juIo33NKhxeAOX3TdmB nvFHyr/ltRxX5/pkhdfnFb3YAQOS7+2makWATXgj9D5MbZvF9itd673IqAWpeuIgk9wU qokA== X-Gm-Message-State: AODbwcAhuXU5kP5s3cHQpy+//TGw//c0r6OjSmYuUhaf8iJ9d3GwAExX 5VTTn4Xm5IlVWUjlOKAnKpDHkLxICg== X-Received: by 10.237.62.115 with SMTP id m48mr10636824qtf.179.1496433866048; Fri, 02 Jun 2017 13:04:26 -0700 (PDT) MIME-Version: 1.0 Sender: earonesty@gmail.com Received: by 10.237.48.102 with HTTP; Fri, 2 Jun 2017 13:04:25 -0700 (PDT) In-Reply-To: References: <1CF1FD5D-8D29-4783-823F-B3F588D5C5CE@mattcorallo.com> From: Erik Aronesty Date: Fri, 2 Jun 2017 16:04:25 -0400 X-Google-Sender-Auth: vJO3WQP5GupYyWfgjpiG5YCiIBA Message-ID: To: =?UTF-8?B?Sm9yZ2UgVGltw7Nu?= , Bitcoin Protocol Discussion Content-Type: multipart/alternative; boundary="001a1140c9a6040d930550ffa95b" X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, FREEMAIL_FROM, HTML_MESSAGE, RCVD_IN_DNSWL_LOW, RCVD_IN_SORBS_SPAM autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org X-Mailman-Approved-At: Fri, 02 Jun 2017 21:26:41 +0000 Subject: Re: [bitcoin-dev] Segwit2Mb - combined soft/hard fork - Request For Comments X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 02 Jun 2017 20:04:29 -0000 --001a1140c9a6040d930550ffa95b Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable 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 Tim=C3=B3n 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 > 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 intern= al > > blockchain building method (test/block_size_tests.cpp). This must be > > replaced soon with a better external test using the bitcoin/qa/rpc-test= s > > 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 > > > wrote: > >> > >> > Remember that the "hashpower required to secure bitcoin" is determin= ed > >> > 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 > >> wrote: > >> > Hey Sergio, > >> > > >> > You appear to have ignored the last two years of Bitcoin hardfork > >> > research and understanding, recycling instead BIP 102 from 2015. The= re > >> > 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 perceive= d > >> > compromise for compromise sake, only making such a hardfork riskier > >> > instead. > >> > > >> > At a minimum, in terms of pure technical changes, you should probabl= y > >> > 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 the= m > 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 f= ix > >> > 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-ca= se > >> > 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 like= ly > >> > be implemented an "additional header" ala Johnson Lau's Spoonnet > >> > proposal. > >> > > >> > Additionally, I think your parameters here pose very significant ris= k > 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 followin= g > >> > several years keeps things nice and continuous and also keeps us fro= m > >> > 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 significantl= y > >> > 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 user= s > >> > 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 determin= ed > >> > 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 pri= ce > >> > 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 Bitcoi= n > 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-d= ev > >> > 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 blockcha= in > >> >>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 proble= m. > >> >> > >> >>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 =3D 1493424000; // April 29th, 2017 > >> >> > >> >>Bit 2 signaling Timeout =3D 1503964800; // August 29th, 2017 > >> >> > >> >>HardForkTime =3D 1513209600; // Thu, 14 Dec 2017 00:00:00 GMT > >> >> > >> >> > >> >>The hard-fork is conditional to 95% of the hashing power has approve= d > >> >>the > >> >>segwit2mb soft-fork and the segwit soft-fork has been activated (whi= ch > >> >>should occur 2016 blocks after its lock-in time) > >> >> > >> >>For more information on how soft-forks are signaled and activated, s= ee > >> >>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 a= nd > >> >>thresholds for all bits. Making segwit and 2Mb fork activate togethe= r > >> >>at a > >> >>delayed date would have required a major re-write of this code, whic= h > >> >>would > >> >>contradict the premise of creating a minimalistic patch. However, on= ce > >> >>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 h= as > >> >>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 c= an > >> >>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 thi= s > >> >>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 delayi= ng > >> >>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-awa= y > >> >>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 suppor= t > >> >>versionbits. Lightweight (SPV) wallets should not be affected as the= y > >> >>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, drivechain= s > >> >>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 transacti= on > >> >>fees > >> >>to put out of business use-cases that could have high positive socia= l > >> >>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 th= e > >> >>patch > >> >>modified more than ~150 lines of code. > >> >> > >> >>Improvements unrelated to a 2 Mb increase or segwit, as beneficial a= s > >> >>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 w= e > >> >>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 > > > _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev > --001a1140c9a6040d930550ffa95b Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
From me to you ...this proposal doesn't lock in anythi= ng. =C2=A0 We could just merge it with some small pushback - allow segwit t= o activate in Aug, then "upgrade" the hard fork to be "spoon= et in 18 months" instead.

On Sat, Apr 1, 2017 at 8:33 AM, Jorge Tim=C3=B3n 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 f= rom 4
mb weight to 8 mb weight.

I would also use the hardfork bit (sign bit in block.nNersion) as matt comm= ents.

> We're in a deadlock and it seems we can't go forward adding mo= re functionality to segwit without the community approval (which include mi= ners). This is obvious to me.Then we have to go back.

If segwit is controversial the way it is (I still don't understa= nd 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 har= d-fork
> signaling, as requested by Matt.
>
> The Segwit2Mb patch can be found here:
> https://github.com/SergioDemia= nLerner/bitcoin/commits/master
>
> For now, the segwit2mb repo has a single test file using the old inter= nal
> blockchain building method (test/block_size_tests.cpp). This must be > replaced soon with a better external test using the bitcoin/qa/rpc-tes= ts
> 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&= quot; is determined
>> > as a percentage of total Bitcoins transacted on-chain in each= block
>>
>> Can you explain this statement a little better?=C2=A0 What do you = mean by
>> that?=C2=A0 What does the total bitcoins transacted have to do wit= h
>> hashpower required?
>>
>>
>> On Fri, Mar 31, 2017 at 2:22 PM, Matt Corallo via bitcoin-dev
>> <bitco= in-dev@lists.linuxfoundation.org> wrote:
>> > Hey Sergio,
>> >
>> > You appear to have ignored the last two years of Bitcoin hard= fork
>> > research and understanding, recycling instead BIP 102 from 20= 15. There
>> > are many proposals which have pushed the state of hard fork r= esearch
>> > much further since then, and you may wish to read some of the= posts on
>> > this mailing list listed at https://bit= coinhardforkresearch.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 r= iskier
>> > 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 n= Version 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 project= s have
>> > already implemented for SegWit in the spending of non-SegWit = outputs.
>> > c) Your really should have replay protection in any HF. The c= lever fix
>> > from
>> > Spoonnet for poor scaling of optionally allowing non-SegWit o= utputs to
>> > be spent with SegWit's sighash provides this all in one g= o.
>> > d) You may wish to consider the possibility of tweaking the w= itness
>> > 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 t= o allow you
>> > to increase the block size while not having a blowup in the w= orst-case
>> > block size.
>> > e) Additional commitments at the top of the merkle root - bot= h for
>> > SegWit transactions and as additional space for merged mining= and other
>> > commitments which we may wish to add in the future, this shou= ld likely
>> > be implemented an "additional header" ala Johnson L= au's Spoonnet
>> > proposal.
>> >
>> > Additionally, I think your parameters here pose very signific= ant risk to
>> > the Bitcoin ecosystem broadly.
>> >
>> > a) Activating a hard fork with less than 18/24 months (and ev= en then...)
>> > from a fully-audited and supported release of full node softw= are to
>> > activation date poses significant risks to many large softwar= e 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 thi= s risk, and
>> > limited pushback on that given the large increase which SegWi= t 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 hardforkin= g, and by
>> > fees changing suddenly. Instead, having the hard fork activat= e technical
>> > changes, and then slowly increasing the block size over the f= ollowing
>> > several years keeps things nice and continuous and also keeps= us from
>> > having to revisit ye old blocksize debate again six months af= ter
>> > activation.
>> >
>> > c) You should likely consider the effect of the many technolo= gical
>> > innovations coming down the pipe in the coming months. Techno= logies like
>> > Lightning, TumbleBit, and even your own RootStock could signi= ficantly
>> > reduce fee pressure as transactions move to much faster and m= ore
>> > featureful systems.
>> >
>> > Commitments to aggressive hard fork parameters now may leave = miners
>> > without much revenue as far out as the next halving (which cu= rrent
>> > transaction growth trends are indicating we'd just only b= arely reach 2MB
>> > of transaction volume, let alone if you consider the effects = of users
>> > moving to systems which provide more features for Bitcoin tra= nsactions).
>> > This could lead to a precipitous drop in hashrate as miners a= re no
>> > longer sufficiently compensated.
>> >
>> > Remember that the "hashpower required to secure bitcoin&= quot; 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 j= ust price
>> > increases. Even if we were OK with hashpower going down compa= red to the
>> > value it is securing, betting the security of Bitcoin on its = price
>> > rising exponentially to match decreasing subsidy does not str= ike me as a
>> > particularly inspiring tradeoff.
>> >
>> > There aren't many great technical solutions to some of th= ese 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 historic= ally never
>> > seen.
>> >
>> > Matt
>> >
>> >
>> > On March 31, 2017 5:09:18 PM EDT, Sergio Demian Lerner via bi= tcoin-dev
>> > <= bitcoin-dev@lists.linuxfoundation.org> wrote:
>> >>Hi everyone,
>> >>
>> >>Segwit2Mb is the project to merge into Bitcoin a minimal p= atch that
>> >>aims to
>> >>untangle the current conflict between different political = positions
>> >>regarding segwit activation vs. an increase of the on-chai= n 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 Bit= coin
>> >>community
>> >>and avoid a cryptocurrency split. Segwit2Mb does not aim t= o be best
>> >>possible technical solution to solve Bitcoin technical lim= itations.
>> >>However, this proposal does not imply a compromise to the = future
>> >>scalability or decentralization of Bitcoin, as a small inc= rease in
>> >>block
>> >>size has been proven by several core and non-core develope= rs 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 w= ithout problem.
>> >>
>> >>On the other side, Segwit2Mb primary goal is to be minimal= istic: 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 th= e time it
>> >>takes
>> >>for core programmers and reviewers to check the correctnes= s of the
>> >>code,
>> >>and to report and correct bugs.
>> >>
>> >>The patch was built by forking the master branch of Bitcoi= n Core,
>> >>mixing a
>> >>few lines of code from Jeff Garzik's BIP102,=C2=A0 and= defining a second
>> >>versionbits activation bit (bit 2) for the combined activa= tion.
>> >>
>> >>The combined activation of segwit and 2Mb hard-fork nVersi= on 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=C2=A0 (DEPLOYMENT_SEGWIT).
>> >>
>> >>The tentative lock-in and hard-fork dates are the followin= g:
>> >>
>> >>Bit 2 signaling StartTime =3D 1493424000; // April 29th, 2= 017
>> >>
>> >>Bit 2 signaling Timeout =3D 1503964800; // August 29th, 20= 17
>> >>
>> >>HardForkTime =3D 1513209600; // Thu, 14 Dec 2017 00:00:00 = GMT
>> >>
>> >>
>> >>The hard-fork is conditional to 95% of the hashing power h= as approved
>> >>the
>> >>segwit2mb soft-fork and the segwit soft-fork has been acti= vated (which
>> >>should occur 2016 blocks after its lock-in time)
>> >>
>> >>For more information on how soft-forks are signaled and ac= tivated, see
>> >>https://github.com/bi= tcoin/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 activa= te 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. H= owever, once
>> >>segwit is activated, the hard-fork is unavoidable.
>> >>
>> >>Although I have coded a first version of the segwit2mb pat= ch (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 comme= nts have been
>> >>received from the community.
>> >>
>> >>To prevent worsening block verification time because of th= e O(N^2)
>> >>hashing
>> >>problem, the simple restriction that transactions cannot b= e larger than
>> >>1Mb
>> >>has been kept. Therefore the worse-case of block verificat= ion time has
>> >>only
>> >>doubled.
>> >>
>> >>Regarding the hard-fork activation date, I want to give en= ough time to
>> >>all
>> >>active economic nodes to upgrade. As of Fri Mar 31 2017, >> >>https://bitnodes.21.co/nodes/ reports that 63= 32 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 0.1= 2 release
>> >>dynamic
>> >>fees were introduced, and currently no Bitcoin automatic p= ayment system
>> >>can
>> >>operate without automatic discovery of the current fee rat= e. 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 ti= me for this
>> >>91%
>> >>to upgrade has been around one year (under a moderate pres= sure 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, an= d it has been
>> >>reviewed and merged and 95% of the hashing power has signa= led for it
>> >>(the
>> >>pressure not to upgrade being a complete halt of the opera= tions).
>> >>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 halt= ing 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 s= hould be
>> >>easily
>> >>ported to other Bitcoin protocol implementations that alre= ady support
>> >>versionbits. Lightweight (SPV) wallets should not be affec= ted as they
>> >>generally do not check the block size.
>> >>
>> >>I personally want to see the Lightning Network in action t= his year, use
>> >>the
>> >>non-malleability features in segwit, see the community dis= cussing 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 posi= tive social
>> >>impact.
>> >>
>> >>I believe in the strength of a unified Bitcoin community. = If you're a
>> >>developer, please give your opinion, suggest changes, audi= t it, and
>> >>take a
>> >>stand with me to unlock the current Bitcoin deadlock.
>> >>
>> >>Contributions to the segwit2mb project are welcomed and aw= aited. The
>> >>only
>> >>limitation is to stick to the principle that the patch sho= uld be as
>> >>simple
>> >>to audit as possible. As an example, I wouldn't feel c= onfident if the
>> >>patch
>> >>modified more than ~150 lines of code.
>> >>
>> >>Improvements unrelated to a 2 Mb increase or segwit, as be= neficial 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 fe= edback is
>> >>expected and welcomed.
>> >>
>> >>Regards,
>> >>Sergio Demian Lerner
>> > _______________________________________________
>> > bitcoin-dev mailing list
>> > bitc= oin-dev@lists.linuxfoundation.org
>> > https://lists.linuxfound= ation.org/mailman/listinfo/bitcoin-dev
>
>
>
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