Bitcoin Optech Newsletter #338 (TL;DR)

Highlights

Draft BIP for Unspendable Keys in Descriptors
A new BIP by Andrew Toth proposes using provably unspendable keys (NUMS points) in descriptors, enhancing Taproot's scriptpath functionality. Discussions are ongoing.

PSBTv2 Integration

• Merklized PSBTv2: The Ledger Bitcoin App uses a Merkle tree approach to handle PSBTv2 data efficiently.

• Silent Payments: BIP352 relies on PSBTv2’s PSBT_OUT_SCRIPT field for enabling silent payment outputs.

Offchain DLC Protocol Correction
The DLC factories protocol allows pre-signed contracts without interactivity, simplifying the renewal process compared to DLC channels, but limits flexibility until maturity.

Updates to Wallets, Services, and Software

• Bull Bitcoin Mobile Wallet: Payjoin (BIP77) send/receive support.

• Bitcoin Keeper: Adds miniscript support in v1.3.0.

• Nunchuk: Beta MuSig2 Taproot multisig support.

• Jade Plus: Air-gapped hardware signing device announced.

• Coinswap v0.1.0: Beta software with testnet4 support.

• Bitcoin Safe 1.0.0: Desktop wallet with hardware integration.

• Rust-payjoin 0.21.0: Transaction cut-through added.

• PeerSwap v4.0rc1: Lightning liquidity protocol upgraded.

• Joinpool Prototype with CTV: Uses OP_CHECKTEMPLATEVERIFY for pooled payments.

• Strata Bridge: A BitVM2-based bridge for Bitcoin-sidechain transfers.

Releases and Testing

• BTCPay Server 2.0.6: Fixes refund/payout vulnerabilities with added features.

Notable Infrastructure Changes

• Bitcoin Core: Enhanced orphan transaction resolution using multiple peers.

• Eclair: MuSig2 prep for Taproot channels.

• LDK: Static invoices and async payments (BOLT12).

• LND: Configurable ProofMatureDelta parameter for gossip announcements.