TERM_DEF // UPGRADES_BIPS / BIP_373_MUSIG2_PSBT_FIELDS
BIP 373 (MUSIG2
PSBT FIELDS)
PSBT FIELDS)
musig2-psbt-fields/">BIP 373 (MuSig2 PSBT Fields). PSBT extensions carrying MuSig2 nonces and partial signatures.
This page sits in the Upgrades & BIPs section — The proposal process and the major upgrades that shaped Bitcoin. Read on for what it is, why it exists, how it works under the hood, and what to watch out for.
This page sits in the Upgrades & BIPs section — The proposal process and the major upgrades that shaped Bitcoin. Read on for what it is, why it exists, how it works under the hood, and what to watch out for.
WHAT_BIP_373_MUSIG2_PSBT_FIELDS_IS
BIP 373 (MuSig2 PSBT Fields) — at a glance
UPGRADES
BIP 373 — "MuSig2 PSBT Fields" is a proposal in the PSBT family, first published in 2024 with status draft. PSBT extensions carrying MuSig2 nonces and partial signatures. Its technical mechanism: per-input fields for participant pubkey, nonce commitments, partial sigs. lets MuSig2 signers coordinate via PSBT files
Why it exists
DESIGN
BIP 373 (MuSig2 PSBT Fields) exists to solve a specific problem: add MuSig2 nonces and partial signatures to PSBT. Without a written, numbered spec, every wallet and node implementer would interpret the requirement differently — and Bitcoin's value depends on every implementation agreeing exactly. BIP-373 is the single source of truth for this concern, so any new client built today can match the behaviour of every client built since 2024.
HOW_IT_WORKS
Mechanism
HOW IT WORKS
Mechanically, BIP-373 per-input fields for participant pubkey, nonce commitments, partial sigs. Adoption today: lets MuSig2 signers coordinate via PSBT files.
1. Author drafts BIP-373 against the BIP-2 template — abstract, motivation, specification, rationale.
2. The text + a reference implementation are posted on the bitcoin-dev list and as a PR to bitcoin/bips.
3. Reviewers tear it apart: ambiguities, security concerns, edge cases, interaction with prior BIPs.
4. Once stable, the BIP editor merges it; it gets a number (BIP-373) and the status "draft" or "proposed".
5. Implementations land in Bitcoin Core / wallets / other clients. For consensus changes: activation parameters chosen.
6. After deployment + adoption, BIP-373 is promoted to "final"; deprecated proposals get "replaced" or "withdrawn".
WORKED_EXAMPLE
BIP-373 — quick reference card
EXAMPLE
BIP number : 373
Title : MuSig2 PSBT Fields
Area : PSBT
First published: 2024
Status : draft
Fork class : no
Motivation : add MuSig2 nonces and partial signatures to PSBT.
Mechanism : per-input fields for participant pubkey, nonce commitments, partial sigs.
Where it shows up : lets MuSig2 signers coordinate via PSBT files.
Read the spec : https://github.com/bitcoin/bips/blob/master/bip-0373.mediawiki
KEY_PROPERTIES
OPT-IN
No authority can force a BIP on anyone. Adoption depends entirely on whether the change is genuinely useful.
NUMBERED
Stable numeric reference — BIP-373 means the same thing across every wallet, miner, and node that has read this spec.
NON-CONSENSUS
BIP-373 is not a consensus rule — clients can implement it without coordinating with the network at large.
DRAFT
BIP-373 is still in draft — reference code may exist but mainnet adoption is partial or pending.
COMMON_PITFALLS
Things that catch people out
PITFALLS
- BIP-373 is still in DRAFT status — its details can change before activation, and any code built against it may need adjustment.
- Don't confuse "draft" / "proposed" / "final" status — read the BIP header before relying on it in production.
- The BIP number is just an editorial counter — it doesn't imply correctness or stability. Always cross-reference with the latest bitcoin/bips repo.
RELATED_CONCEPTS
Other terms from Upgrades & BIPs — click any to read its page:
TERMINOLOGY_INDEX
TERMINOLOGY
BIP 373 (MuSig2 PSBT Fields)
PSBT extensions carrying MuSig2 nonces and partial signatures.
Segregated Witness (SegWit, BIP 141)
The 2017 upgrade separating witness-data/">witness data, fixing tx malleability, and introducing weight units.
Taproot (BIP 341)
Tapscript (BIP 342)
Script-language updates accompanying Taproot — new opcodes, removed limits.
Schnorr (BIP 340)
The Schnorr signature spec adopted by Taproot.
BIP Process
The community workflow for proposing, discussing, and tracking changes to Bitcoin.
Soft Fork Activation
MASF (Miner-Activated Soft Fork)
Activation triggered by miner signaling in block versions.