BIP-91 (reduced-threshold SegWit signalling)
James Hilliard's 2017 miner-enforced bridge: an 80% vote over 336 blocks that made miners reject blocks not signalling SegWit, letting the original 95% deployment lock in.
The wiki's angle: BIP-91 was the face-saving mechanism of 2017 — miners could say they had activated SegWit on their own terms while the UASF deadline did the pushing.[3][5]
Contents
Mechanism
BIP-91, “Reduced threshold Segwit MASF”, is authored by James Hilliard[1]. While active, it requires all blocks to signal the existing SegWit deployment (bit 1); “Blocks that do not signal as required will be rejected”[1]. It is deployed with version bits under the name “segsignal” on bit 4, with an 80% threshold of 269 blocks in a 336-block window, starting on 1 June 2017 and timing out on 15 November 2017[1]. The Bitcoin Wiki copy gives its creation date as 2017-05-22[2].
2017
Bitcoin Takeover's Fork Wars timeline says “BIP 91 locked in on 21 July 2017 and activated on 26 July”, after which the original BIP-9 SegWit threshold could be met; SegWit locked in on 9 August and activated on 24 August at block 481,824[3]. The forks overview calls BIP-91 a “Miner-enforced bridge”[4]. It ran alongside BIP-148, which had nodes reject non-signalling blocks from 1 August 2017[5].
Hilliard
The February 2016 Hong Kong Roundtable statement lists “James Hilliard Pool/Farm Admin BitmainWarranty” among its signers[6].
References
- primaryBIP-91 (Reduced threshold Segwit MASF) [archived]
- secondaryBitcoin Wiki mirror of BIP 91 (Created: 2017-05-22; Status: Final) [archived]
- btkFork Wars: the block size war timeline (Bitcoin Takeover) [archived]
- btkBitcoin: All the Hard Forks and Soft Forks (BTCTKVR: Forks!) [archived]
- primaryBIP-148 (Mandatory activation of segwit deployment), Shaolin Fry [archived]
- primaryBitcoin Roundtable, “Bitcoin Roundtable Consensus”, Medium, 20 Feb 2016 (Wayback Machine copy)