MuSig2 for BIP340-compatible Multi-Signatures.

Lets several people combine their keys into one and sign together, producing what looks like a single ordinary signature.

With MuSig2, a group shares control of a Taproot output that looks on the blockchain like it belongs to one person. Spending needs every member to sign, but only one key and one signature are recorded, which saves space and improves privacy. Everyone in the group must take part.