Re: [bitcoin-dev] User Activated Soft Fork Split Protection

From: Erik Aronesty <erik@q32•com>
To: Jacob Eliosoff <jacob.eliosoff@gmail•com>
Cc: Bitcoin Dev <bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] User Activated Soft Fork Split Protection
Date: Wed, 7 Jun 2017 14:05:52 -0400	[thread overview]
Message-ID: <CAJowKgK52vo8c2v2AoSMoTzdL_YsHPNGZqJOy1HWPRdBPTb1uw@mail.gmail.com> (raw)
In-Reply-To: <CAAUaCyiKs9cDa6vC=8VpyT8vY5L8U0=H=+N48dJzLn1GMj3dmA@mail.gmail.com>

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> But passing it off as the safest defense is bad faith.

Without this option, a miner has to guess whether a split will be
economically impacting.   With this option, his miner will automatically
switch to the chain least likely to get wiped out... as soon as a simple
majority of miners supports it.

On Wed, Jun 7, 2017 at 12:44 PM, Jacob Eliosoff <jacob.eliosoff@gmail•com>
wrote:

> This is not the safest defense against a split.  If 70% of miners run
> "splitprotection", and 0.1% run BIP148, there's no "safety"/"defense"
> reason for splitprotection to activate segwit.  It should only do so if
> *BIP148* support (NB: not just segwit support!) >50%.
>
> The truly defensive logic is "If the majority supports orphaning
> non-segwit blocks starting Aug 1, I'll join them."
>
> If the real goal of this BIP is to induce miners to run segwit, then fair
> enough.  But passing it off as the safest defense is bad faith.
>
>
> On Wed, Jun 7, 2017 at 10:10 AM, Erik Aronesty via bitcoin-dev <
> bitcoin-dev@lists•linuxfoundation.org> wrote:
>
>> This is, by far, the safest way for miners to quickly defend against a
>> chain split, much better than a -bip148 option.   This allows miners to
>> defend themselves, with very little risk, since the defense is only
>> activated if the majority of miners do so. I would move for a very rapid
>> deployment.   Only miners would need to upgrade.   Regular users would not
>> have to concern themselves with this release.
>>
>> On Wed, Jun 7, 2017 at 6:13 AM, James Hilliard via bitcoin-dev <
>> bitcoin-dev@lists•linuxfoundation.org> wrote:
>>
>>> I think even 55% would probably work out fine simply due to incentive
>>> structures, once signalling is over 51% it's then clear to miners that
>>> non-signalling blocks will be orphaned and the rest will rapidly
>>> update to splitprotection/BIP148. The purpose of this BIP is to reduce
>>> chain split risk for BIP148 since it's looking like BIP148 is going to
>>> be run by a non-insignificant percentage of the economy at a minimum.
>>>
>>> On Wed, Jun 7, 2017 at 12:20 AM, Tao Effect <contact@taoeffect•com>
>>> wrote:
>>> > See thread on replay attacks for why activating regardless of
>>> threshold is a
>>> > bad idea [1].
>>> >
>>> > BIP91 OTOH seems perfectly reasonable. 80% instead of 95% makes it more
>>> > difficult for miners to hold together in opposition to Core. It gives
>>> Core
>>> > more leverage in negotiations.
>>> >
>>> > If they don't activate with 80%, Core can release another BIP to
>>> reduce it
>>> > to 75%.
>>> >
>>> > Each threshold reduction makes it both more likely to succeed, but also
>>> > increases the likelihood of harm to the ecosystem.
>>> >
>>> > Cheers,
>>> > Greg
>>> >
>>> > [1]
>>> > https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017
>>> -June/014497.html
>>> >
>>> > --
>>> > Please do not email me anything that you are not comfortable also
>>> sharing
>>> > with the NSA.
>>> >
>>> > On Jun 6, 2017, at 6:54 PM, James Hilliard <james.hilliard1@gmail•com>
>>> > wrote:
>>> >
>>> > This is a BIP8 style soft fork so mandatory signalling will be active
>>> > after Aug 1st regardless.
>>> >
>>> > On Tue, Jun 6, 2017 at 8:51 PM, Tao Effect <contact@taoeffect•com>
>>> wrote:
>>> >
>>> > What is the probability that a 65% threshold is too low and can allow a
>>> > "surprise miner attack", whereby miners are kept offline before the
>>> > deadline, and brought online immediately after, creating potential
>>> havoc?
>>> >
>>> > (Nit: "simple majority" usually refers to >50%, I think, might cause
>>> > confusion.)
>>> >
>>> > -Greg Slepak
>>> >
>>> > --
>>> > Please do not email me anything that you are not comfortable also
>>> sharing
>>> > with the NSA.
>>> >
>>> > On Jun 6, 2017, at 5:56 PM, James Hilliard via bitcoin-dev
>>> > <bitcoin-dev@lists•linuxfoundation.org> wrote:
>>> >
>>> > Due to the proposed calendar(https://segwit2x.github.io/) for the
>>> > SegWit2x agreement being too slow to activate SegWit mandatory
>>> > signalling ahead of BIP148 using BIP91 I would like to propose another
>>> > option that miners can use to prevent a chain split ahead of the Aug
>>> > 1st BIP148 activation date.
>>> >
>>> > The splitprotection soft fork is essentially BIP91 but using BIP8
>>> > instead of BIP9 with a lower activation threshold and immediate
>>> > mandatory signalling lock-in. This allows for a majority of miners to
>>> > activate mandatory SegWit signalling and prevent a potential chain
>>> > split ahead of BIP148 activation.
>>> >
>>> > This BIP allows for miners to respond to market forces quickly ahead
>>> > of BIP148 activation by signalling for splitprotection. Any miners
>>> > already running BIP148 should be encouraged to use splitprotection.
>>> >
>>> > <pre>
>>> > BIP: splitprotection
>>> > Layer: Consensus (soft fork)
>>> > Title: User Activated Soft Fork Split Protection
>>> > Author: James Hilliard <james.hilliard1@gmail•com>
>>> > Comments-Summary: No comments yet.
>>> > Comments-URI:
>>> > Status: Draft
>>> > Type: Standards Track
>>> > Created: 2017-05-22
>>> > License: BSD-3-Clause
>>> >          CC0-1.0
>>> > </pre>
>>> >
>>> > ==Abstract==
>>> >
>>> > This document specifies a coordination mechanism for a simple majority
>>> > of miners to prevent a chain split ahead of BIP148 activation.
>>> >
>>> > ==Definitions==
>>> >
>>> > "existing segwit deployment" refer to the BIP9 "segwit" deployment
>>> > using bit 1, between November 15th 2016 and November 15th 2017 to
>>> > activate BIP141, BIP143 and BIP147.
>>> >
>>> > ==Motivation==
>>> >
>>> > The biggest risk of BIP148 is an extended chain split, this BIP
>>> > provides a way for a simple majority of miners to eliminate that risk.
>>> >
>>> > This BIP provides a way for a simple majority of miners to coordinate
>>> > activation of the existing segwit deployment with less than 95%
>>> > hashpower before BIP148 activation. Due to time constraints unless
>>> > immediately deployed BIP91 will likely not be able to enforce
>>> > mandatory signalling of segwit before the Aug 1st activation of
>>> > BIP148. This BIP provides a method for rapid miner activation of
>>> > SegWit mandatory signalling ahead of the BIP148 activation date. Since
>>> > the primary goal of this BIP is to reduce the chance of an extended
>>> > chain split as much as possible we activate using a simple miner
>>> > majority of 65% over a 504 block interval rather than a higher
>>> > percentage. This BIP also allows miners to signal their intention to
>>> > run BIP148 in order to prevent a chain split.
>>> >
>>> > ==Specification==
>>> >
>>> > While this BIP is active, all blocks must set the nVersion header top
>>> > 3 bits to 001 together with bit field (1<<1) (according to the
>>> > existing segwit deployment). Blocks that do not signal as required
>>> > will be rejected.
>>> >
>>> > ==Deployment==
>>> >
>>> > This BIP will be deployed by "version bits" with a 65%(this can be
>>> > adjusted if desired) activation threshold BIP9 with the name
>>> > "splitprotecion" and using bit 2.
>>> >
>>> > This BIP starts immediately and is a BIP8 style soft fork since
>>> > mandatory signalling will start on midnight August 1st 2017 (epoch
>>> > time 1501545600) regardless of whether or not this BIP has reached its
>>> > own signalling threshold. This BIP will cease to be active when segwit
>>> > is locked-in.
>>> >
>>> > === Reference implementation ===
>>> >
>>> > <pre>
>>> > // Check if Segregated Witness is Locked In
>>> > bool IsWitnessLockedIn(const CBlockIndex* pindexPrev, const
>>> > Consensus::Params& params)
>>> > {
>>> >   LOCK(cs_main);
>>> >   return (VersionBitsState(pindexPrev, params,
>>> > Consensus::DEPLOYMENT_SEGWIT, versionbitscache) ==
>>> > THRESHOLD_LOCKED_IN);
>>> > }
>>> >
>>> > // SPLITPROTECTION mandatory segwit signalling.
>>> > if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(),
>>> > Consensus::DEPLOYMENT_SPLITPROTECTION, versionbitscache) ==
>>> > THRESHOLD_LOCKED_IN &&
>>> >    !IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
>>> > // Segwit is not locked in
>>> >    !IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus()) ) //
>>> > and is not active.
>>> > {
>>> >   bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
>>> > VERSIONBITS_TOP_BITS;
>>> >   bool fSegbit = (pindex->nVersion &
>>> > VersionBitsMask(chainparams.GetConsensus(),
>>> > Consensus::DEPLOYMENT_SEGWIT)) != 0;
>>> >   if (!(fVersionBits && fSegbit)) {
>>> >       return state.DoS(0, error("ConnectBlock(): relayed block must
>>> > signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
>>> >   }
>>> > }
>>> >
>>> > // BIP148 mandatory segwit signalling.
>>> > int64_t nMedianTimePast = pindex->GetMedianTimePast();
>>> > if ( (nMedianTimePast >= 1501545600) &&  // Tue 01 Aug 2017 00:00:00
>>> UTC
>>> >    (nMedianTimePast <= 1510704000) &&  // Wed 15 Nov 2017 00:00:00 UTC
>>> >    (!IsWitnessLockedIn(pindex->pprev, chainparams.GetConsensus()) &&
>>> > // Segwit is not locked in
>>> >     !IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) )
>>> > // and is not active.
>>> > {
>>> >   bool fVersionBits = (pindex->nVersion & VERSIONBITS_TOP_MASK) ==
>>> > VERSIONBITS_TOP_BITS;
>>> >   bool fSegbit = (pindex->nVersion &
>>> > VersionBitsMask(chainparams.GetConsensus(),
>>> > Consensus::DEPLOYMENT_SEGWIT)) != 0;
>>> >   if (!(fVersionBits && fSegbit)) {
>>> >       return state.DoS(0, error("ConnectBlock(): relayed block must
>>> > signal for segwit, please upgrade"), REJECT_INVALID, "bad-no-segwit");
>>> >   }
>>> > }
>>> > </pre>
>>> >
>>> > https://github.com/bitcoin/bitcoin/compare/0.14...jameshilli
>>> ard:splitprotection-v0.14.1
>>> >
>>> > ==Backwards Compatibility==
>>> >
>>> > This deployment is compatible with the existing "segwit" bit 1
>>> > deployment scheduled between midnight November 15th, 2016 and midnight
>>> > November 15th, 2017. This deployment is also compatible with the
>>> > existing BIP148 deployment. This BIP is compatible with BIP91 only if
>>> > BIP91 activates before it and before BIP148. Miners will need to
>>> > upgrade their nodes to support splitprotection otherwise they may
>>> > build on top of an invalid block. While this bip is active users
>>> > should either upgrade to splitprotection or wait for additional
>>> > confirmations when accepting payments.
>>> >
>>> > ==Rationale==
>>> >
>>> > Historically we have used IsSuperMajority() to activate soft forks
>>> > such as BIP66 which has a mandatory signalling requirement for miners
>>> > once activated, this ensures that miners are aware of new rules being
>>> > enforced. This technique can be leveraged to lower the signalling
>>> > threshold of a soft fork while it is in the process of being deployed
>>> > in a backwards compatible way. We also use a BIP8 style timeout to
>>> > ensure that this BIP is compatible with BIP148 and that BIP148
>>> > compatible mandatory signalling activates regardless of miner
>>> > signalling levels.
>>> >
>>> > By orphaning non-signalling blocks during the BIP9 bit 1 "segwit"
>>> > deployment, this BIP can cause the existing "segwit" deployment to
>>> > activate without needing to release a new deployment. As we approach
>>> > BIP148 activation it may be desirable for a majority of miners to have
>>> > a method that will ensure that there is no chain split.
>>> >
>>> > ==References==
>>> >
>>> > *[https://lists.linuxfoundation.org/pipermail/bitcoin-dev/20
>>> 17-March/013714.html
>>> > Mailing list discussion]
>>> > *[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cp
>>> p#L1281-L1283
>>> > P2SH flag day activation]
>>> > *[[bip-0009.mediawiki|BIP9 Version bits with timeout and delay]]
>>> > *[[bip-0016.mediawiki|BIP16 Pay to Script Hash]]
>>> > *[[bip-0091.mediawiki|BIP91 Reduced threshold Segwit MASF]]
>>> > *[[bip-0141.mediawiki|BIP141 Segregated Witness (Consensus layer)]]
>>> > *[[bip-0143.mediawiki|BIP143 Transaction Signature Verification for
>>> > Version 0 Witness Program]]
>>> > *[[bip-0147.mediawiki|BIP147 Dealing with dummy stack element
>>> malleability]]
>>> > *[[bip-0148.mediawiki|BIP148 Mandatory activation of segwit
>>> deployment]]
>>> > *[[bip-0149.mediawiki|BIP149 Segregated Witness (second deployment)]]
>>> > *[https://bitcoincore.org/en/2016/01/26/segwit-benefits/ Segwit
>>> benefits]
>>> >
>>> > ==Copyright==
>>> >
>>> > This document is dual licensed as BSD 3-clause, and Creative Commons
>>> > CC0 1.0 Universal.
>>> > _______________________________________________
>>> > 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
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>>
>>
>

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