MuSig explained Simply
MuSig is a protocol for aggregating public keys and Schnorr signatures.
It allows multiple participants (A and B) to jointly sign a transaction as if it came from a single key.
It allows multiple participants (A and B) to jointly sign a transaction as if it came from a single key.
If we want to spend funds locked in P_AB,
we sign the transaction by aggregating
we sign the transaction by aggregating
S_A and S_B:
S_AB = S_A + S_B✅ Pros
- Saves block space
- Improves privacy
- Faster verification
❌ Cons
- Requires multiple rounds of interaction between signers
Let’s dive deeper into the issue of interactivity
Creating a MuSig signature
S_AB requires 3 rounds of communication between A and B:Before explaining the 3 rounds of communication
let me first show you the Schnorr signature equation.
where:
x= private keyk= nonce (you pick it randomly)h = H(R || P || m)
Each signer computes:
s_i = k_i + H(X, R, m) * x_i🧩 After aggregation
Now the aggregated signature becomes:
s = (k1 + k2) + H(X, R, m)(x1 + x2)To create the aggregated signature
each participant needs the nonce k from the other participants.
S_AB,each participant needs the nonce k from the other participants.
🔄 Round 1
Exchange nonce commitment
🔄 Round 2
Exchange nonces
🔄 Round 3
Exchange partial signatures
After this, each participant can compute the final Schnorr signature:
🧠 MuSig2 Fixes This
It requires only two rounds of communication 🎯
We’ll take a deep dive into MuSig2 in the next post.
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