This week’s newsletter links to comparisons between different cluster linearization techniques and briefly summarizes discussion about increasing or removing Bitcoin Core’s OP_RETURN size limit. Also included are our regular sections announcing new releases and release candidates and summarizing notable changes to popular Bitcoin infrastructure software.

News

  • ● Comparison of cluster linearization techniques: Pieter Wuille posted to Delving Bitcoin about some of the fundamental tradeoffs between three different cluster linearization techniques, following up with benchmarks of implementations of each. Several other developers discussed the results and asked clarifying questions, to which Wuille responded.

  • ● Increasing or removing Bitcoin Core’s OP_RETURN size limit: in a thread on Bitcoin-Dev, several developers discussed changing or removing Bitcoin Core’s default limit for OP_RETURN data carrier outputs. A subsequent Bitcoin Core pull request saw additional discussion. Rather than attempt to summarize the entire voluminous discussion, we’ll summarize what we thought was the most compelling argument for and against the change.

    • ● For increasing (or eliminating) the limit: Pieter Wuille argued that transaction standardness policy is unlikely to significantly prevent confirmation of data carrying transactions created by well-funded organizations that will put the effort into sending the transactions directly to miners. Additionally, he argues that blocks are generally full whether or not they contain data-carrying transactions, so the overall amount of data a node needs to store is roughly the same either way.

    • ● Against increasing the limit: Jason Hughes argued that increasing the limit would make it easier to store arbitrary data on computers running full nodes, and that some of that data could be highly objectionable (including illegal in most jurisdictions). Even if the node encrypts the data on disk (see Newsletter #316), storage of the data and the ability to retrieve it using Bitcoin Core RPCs could be problematic for many users.

Releases and release candidates

New releases and release candidates for popular Bitcoin infrastructure projects. Please consider upgrading to new releases or helping to test release candidates.

  • ● LND 0.19.0-beta.rc3 is a release candidate for this popular LN node. One of the major improvements that could probably use testing is the new RBF-based fee bumping for cooperative closes.

Notable code and documentation changes

Notable recent changes in Bitcoin Core, Core Lightning, Eclair, LDK, LND, libsecp256k1, Hardware Wallet Interface (HWI), Rust Bitcoin, BTCPay Server, BDK, Bitcoin Improvement Proposals (BIPs), Lightning BOLTs, Lightning BLIPs, Bitcoin Inquisition, and BINANAs.

  • ● Bitcoin Core #31250 disables the creation and loading of legacy wallets, completing the migration to descriptor wallets that have been the default since October 2021 (see Newsletter #172). Berkeley DB files used by legacy wallets can no longer be loaded, and all unit and functional tests for legacy wallets are deleted. Some legacy wallet code remains, but will be removed in follow up PRs. Bitcoin Core is still able to migrate legacy wallets to the new descriptor wallet format (see Newsletter #305).

  • ● Eclair #3064 refactors channel key management by introducing a ChannelKeys class. Each channel now has its own ChannelKeys object which, together with the commitment points, derives a CommitmentKeys set for signing remote/local commitment and HTLC transactions. The force close logic and script/witness creation are also updated to rely on CommitmentKeys. Previously, key generation was scattered across several parts of the codebase to support external signers, which was prone to errors because it relied on naming rather than types to ensure the correct pubkey was provided.

  • ● BTCPay Server #6684 adds support for a subset of BIP388 wallet policy descriptors, allowing users to import and export both single-sig and k-of-n policies. It includes the formats supported by Sparrow such as P2PKH, P2WPKH, P2SH-P2WPKH, and P2TR, with corresponding multisig variants, except for P2TR. Improving the use of multisig wallets is the intended goal of this PR.

  • ● BIPs #1555 merges BIP321, which proposes a URI scheme for describing bitcoin payment instructions that modernizes and extends BIP21. It keeps the legacy path‐based address but standardizes the use of query parameters by making new payment methods identifiable by their own parameters, and allows the address field to be left empty if at least one instruction appears in a query parameter. It adds an optional extension to provide a proof of payment to the spender, and provides guidance on how to incorporate new payment instructions.

Want more?

For more discussion about the topics mentioned in this newsletter, join us for the weekly Bitcoin Optech Recap on Riverside.fm at 16:30 UTC on May 6. The discussion is also recorded and will be available from our podcasts page.