[bitcoin-dev] The BIP148 chain split may be inevitable

I've been trying to work out the expected interaction between James Hilliard's BIP91 [1] (or splitprotection [2], or Segwit2x [3], which both use variants of BIP91 activation) and the BIP148 UASF [4]. Some of this is subtle so CORRECTIONS WELCOME, but my conclusions are: 1. It's extremely unlikely BIP91-type logic can activate segwit in time to avoid a BIP148 chain split. 2. So, in practice all we can do is ensure the BIP148 split is as painless as possible. REASONING: First, some dates. BIP148, whose deadline is already deployed and thus unlikely to be postponed, starts orphaning non-segwit blocks on midnight (GMT) the morning of August 1. Meanwhile, here are Bitcoin's rough expected next four difficulty adjustment dates (they could vary by ~1-3 days depending on block times, but it's unlikely to matter here): 1. June 17 2. June 30 3. July 13 4. July 27 If Segwit activates on adj date #5 or later (August), it will be too late to avoid BIP148's split, which will have occurred the moment August began. So, working backwards, and assuming we want compatibility with old BIP141 nodes: - Segwit MUST activate by adj #4 (~July 27) - Therefore segwit MUST be locked in by adj #3 (~July 13: this is inflexible, since this logic is in already-deployed BIP141 nodes) - Therefore, I *think* >50% of hashpower needs to be BIP91 miners, signaling bit 1 and orphaning non-BIP91 (ie, BIP91's bit 4 must activate), by adj #2 (June 30)? - Therefore, as currently designed, BIP91 bit 4 must be locked in by adj #1 (June 17) - Therefore, >=80% of hashrate must start signaling BIP91's bit 4 by a few days ago... There are ways parts of this could be sped up, eg, James' "rolling 100-block lock-in periods" [5], to get BIP91 signaling bit 1 sooner. But to be compatible with old BIP141 nodes, >50% of hashrate must be activated BIP91 miners by ~June 30: there's no fudging that. So, it seems to me that to avoid the BIP148 split, one of two things would have to happen: a) 95% of hashrate start signaling bit 1 by ~June 30. Given current stat is 32%, this would basically require magic. b) BIP91 is deployed and >50% (80% or whatever) of hashrate is *activated* BIP91 miners by ~June 30, ~3 weeks from now. Again, much too soon. So, I think the BIP148 split is inevitable. I actually expect that few parts of the ecosystem will join the fork, so disruption will be bearable. But anyway let me know any flaws in the reasoning above. [1] https://github.com/bitcoin/bips/blob/master/bip-0091.mediawiki [2] https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2017-June/014508.html [3] https://github.com/btc1/bitcoin/pull/11 [4] https://github.com/bitcoin/bips/blob/master/bip-0148.mediawiki [5] https://github.com/btc1/bitcoin/pull/6#issuecomment-305917729 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.linuxfoundation.org/pipermail/bitcoin-dev/attachments/20170609/e606bbb0/attachment-0001.html>