BIP 373 guide to MuSig2 participant, public-nonce and partial-signature PSBT fields, signer roles, Taproot context, nonce safety and finalisation.
This guide explains BIP 373 MuSig2 PSBT Fields in plain English. It covers the problem behind the BIP, why it matters and whether the proposal is part of Bitcoin today.
BIP 373 MuSig2 PSBT Fields: Updaters assemble context, signers verify and add round data, and finalizers combine valid partial signatures and remove fields according to the specification.
A node operator is checking BIP 373 MuSig2 PSBT Fields. Persist session identifiers atomically, reject changed PSBT data after commitment and test interrupted and duplicated workflows.
BIP 373 is Complete, Specification, and depends on BIPs 32, 174, 327, 328 and 370. It extends PSBT interchange rather than Bitcoin consensus.
The participant field is keyed by the compressed aggregate public key and contains compressed participant keys in aggregation order. If KeySort was used, the sorted order must be preserved.
Each public-nonce field identifies the participant, aggregate key and optional tapleaf hash, then stores the 66-byte public nonce produced by MuSig2 NonceGen.
The partial-signature field uses the corresponding identity tuple and carries a 32-byte partial signature. It must bind to the same transaction, input, aggregate key and leaf context.
The tapleaf hash is omitted for an internal-key or output-key spend and supplied for a script leaf. Do not substitute a parent aggregate key where the output or script participant key is required.
Updaters assemble context, signers verify and add round data, and finalizers combine valid partial signatures and remove fields according to the specification. Capability checks remain local.
Never reuse secret nonce material across messages, inputs or aborted sessions. Persist session identifiers atomically, reject changed PSBT data after commitment and test interrupted and duplicated workflows. Build a revision-pinned evidence pack on an isolated node, wallet or protocol harness.
BIP 373 MuSig2 PSBT Fields: Updaters assemble context, signers verify and add round data, and finalizers combine valid partial signatures and remove fields according to the specification.
BIP 373 is Complete, Specification, and depends on BIPs 32, 174, 327, 328 and 370.
The participant field is keyed by the compressed aggregate public key and contains compressed participant keys in aggregation order.
Each public-nonce field identifies the participant, aggregate key and optional tapleaf hash, then stores the 66-byte public nonce produced by MuSig2 NonceGen.
BIP 373 makes MuSig2 coordination portable through PSBT, but it cannot replace signer-side transaction validation or nonce discipline. Each participant should treat the PSBT as untrusted state and prove every field before signing.
Check the current specification status and the documentation for the exact implementation you operate before moving production funds or changing a mining node.
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