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 <cont...@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.hillia...@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 <cont...@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.hillia...@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...jameshilliard: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/2017-March/013714.html > Mailing list discussion] > *[https://github.com/bitcoin/bitcoin/blob/v0.6.0/src/main.cpp#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
