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MuSig2 ​

This directory contains documentation for MuSig2 (BIP327) multisignature implementation.

Contents ​

DocumentDescriptionAudience
user-guide.mdHow to use MuSig2 for multisig operationsOperators
architecture.mdMuSig2 system architecture and data flowDevelopers
security.mdSecurity considerations and nonce managementAll
migration-from-traditional.mdMigration guide from traditional P2WSH multisigAll

What is MuSig2? ​

MuSig2 is a two-round Schnorr multisignature protocol (BIP327) that enables N-of-N multisig appearing as single-sig on-chain:

  • Smaller Transactions: 30-50% size reduction vs traditional P2WSH multisig
  • Lower Fees: Proportional to transaction size reduction
  • Better Privacy: Multisig transactions look like single-sig on-chain
  • Schnorr Signatures: Uses BIP340 via Taproot (P2TR)

Two-Round Protocol ​

Round 1: Nonce Generation (Parallel)
├── Each signer generates random nonce
├── Public nonces are exchanged
└── Aggregate nonce computed

Round 2: Partial Signing (Sequential)
├── Each signer creates partial signature
├── Partial signatures are collected
└── Aggregated into single 64-byte Schnorr signature

⚠️ Critical Security: Nonce Management ​

NEVER reuse nonces - Reusing nonces in MuSig2 will leak the private key!

  • Generate fresh nonces for every transaction
  • Delete nonces immediately after signing
  • See security.md for details

CLI Commands ​

bash
# Create MuSig2 address
keygen --coin btc create musig2-address

# Generate nonces
keygen --coin btc musig2 nonce
sign --coin btc musig2 nonce

# Create partial signatures
keygen --coin btc musig2 sign
sign --coin btc musig2 sign

# Aggregate signatures
watch --coin btc musig2 aggregate

References ​