Bitcoin Optech Newsletter #429

Bitcoin Optech Newsletter #429 covers a new protocol for silent payment transactions from multiparty wallets, details a denial-of-service vulnerability affecting older Core Lightning versions, and explains Bitcoin Core's updated security policy for easily discoverable vulnerabilities. The newsletter also includes regular sections with Bitcoin Stack Exchange Q&A, new releases, and notable changes to Bitcoin infrastructure software. Key news includes Oleksandr Kurbatov's proposal on Delving Bitcoin for a protocol to enable multiparty inputs in silent payment transactions. This addresses BIP352's current recommendation against such inputs due to a lack of security proof. The proposed protocol allows a multiparty sender to compute the ECDH share as a weighted sum of signers' contributions, secured by an aggregated DLEQ proof (AggDLEQ) which proves the ECDH share's correct derivation from the input key. This design is compatible with existing multiparty protocols like FROST and MuSig2. The process involves a two-round interaction where a coordinator provides context, signers generate nonces and initial messages for AggDLEQ, and then contribute to a final proof based on a challenge. Kurbatov asserts that this protocol requires no modifications to BIP352, BIP374, BIP375, MuSig2, or FROST.