Hi James, >From what I understand, this proposal is incompatible with the current segwit implementation with regards to the NODE_WITNESS service bit. I believe it could cause network partitioning if the service bit is not changed.
Andrew On 5/22/2017 6:40 PM, James Hilliard via bitcoin-dev wrote: > I would like to propose an implementation that accomplishes the first > part of the Barry Silbert proposal independently from the second: > > "Activate Segregated Witness at an 80% threshold, signaling at bit 4" > in a way that > > The goal here is to minimize chain split risk and network disruption > while maximizing backwards compatibility and still providing for rapid > activation of segwit at the 80% threshold using bit 4. > > By activating segwit immediately and separately from any HF we can > scale quickly without risking a rushed combined segwit+HF that would > almost certainly cause widespread issues. > > Draft proposal: > https://github.com/jameshilliard/bips/blob/bip-segsignal/bip-segsignal.mediawiki > > Proposal text: > <pre> > BIP: segsignal > Layer: Consensus (soft fork) > Title: Reduced signalling threshold activation of existing segwit deployment > Author: James Hilliard <james.hillia...@gmail.com> > Status: Draft > Type: Standards Track > Created: 2017-05-22 > License: BSD-3-Clause > CC0-1.0 > </pre> > > ==Abstract== > > This document specifies a method to activate the existing BIP9 segwit > deployment with a majority hashpower less than 95%. > > ==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== > > Segwit increases the blocksize, fixes transaction malleability, and > makes scripting easier to upgrade as well as bringing many other > [https://bitcoincore.org/en/2016/01/26/segwit-benefits/ benefits]. > > This BIP provides a way for a simple majority of miners to coordinate > activation of the existing segwit deployment with less than 95% > hashpower. For a number of reasons a complete redeployment of segwit > is difficulty to do until the existing deployment expires. This is due > to 0.13.1+ having many segwit related features active already, > including all the P2P components, the new network service flag, the > witness-tx and block messages, compact blocks v2 and preferential > peering. A redeployment of segwit will need to redefine all these > things and doing so before expiry would greatly complicate testing. > > ==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 a "version bits" with an 80%(this can be > adjusted if desired) activation threshold BIP9 with the name > "segsignal" and using bit 4. > > This BIP will have a start time of midnight June 1st, 2017 (epoch time > 1496275200) and timeout on midnight November 15th 2017 (epoch time > 1510704000). 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); > } > > // SEGSIGNAL mandatory segwit signalling. > if ( VersionBitsState(pindex->pprev, chainparams.GetConsensus(), > Consensus::DEPLOYMENT_SEGSIGNAL, versionbitscache) == THRESHOLD_ACTIVE > && > !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:segsignal-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. Miners will need to upgrade their nodes to > support segsignal otherwise they may build on top of an invalid block. > While this bip is active users should either upgrade to segsignal 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. > > 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. > > ==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-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
