Reduced signalling threshold activation of existing segwit deployment

Summary:

This context is a discussion thread that was posted on bitcoin-dev mailing list. The discussion was about the proposal to activate segregated witness (SegWit) at an 80% threshold by signaling at bit 4. The proposal was put forward by James Hilliard as a way of minimizing chain split risk and maximizing backward compatibility while providing rapid activation of SegWit at the 80% threshold using bit 4. The proposal specifies a method to activate the existing BIP9 SegWit deployment with a majority hash power less than 95%. The proposal also aims to scale quickly without risking a rushed combined SegWit+HF that would almost certainly cause widespread issues. While this BIP is active, all blocks must set the nVersion header top 3 bits to 001 together with bit field (1<<<<28). Miners will need to upgrade their nodes to support segsignal otherwise they may build on top of an invalid block. The proposal text also highlights several benefits of SegWit such as increasing the block size, fixing transaction malleability, and making scripting easier to upgrade as well as bringing many other benefits. The proposal has received feedback from various participants in the form of emails. For instance, Wang Chun suggested going for a 75% threshold, same as Litecoin. Andrew Chow raised concerns about the proposal's compatibility with the current SegWit implementation with regards to the NODE_WITNESS service bit. James Hilliard clarified that the proposal is compatible with the current SegWit implementation because it triggers a mandatory signaling period that will activate SegWit on existing nodes. Andrew Chow also suggested setting the timeout date for before the BIP141 timeout to avoid locking in but not having enough time for SegWit to be locked in. Overall, the discussion provides insights into the technicalities of activating SegWit and the different perspectives that exist regarding the process.

Updated on: 2023-06-12T01:10:22.567033+00:00