With Bitcoin’s long-awaited Taproot upgrade on the horizon, the engineers at Blockstream are working on a new scheme to improve multi-signature transactions.
These transactions, which require signatures from more than one private key to authorize spends, will stand to benefit from Taproot. This upgrade implements Schnorr signatures into Bitcoin’s codebase, a cryptographic signature scheme that will make creating and executing smart contracts easier on the network.
In a post-election day blog post, Blockstream engineers Jonas Nick and Tim Ruffing lay out a new multi-signature design that would reduce the technical complexity of multi-signature transactions in a way that still preserves privacy.
Nick and Ruffing, alongside French National Security Agency member Yannick Seurin, published a cryptographic e-journal on this MuSig2 design that is currently undergoing peer review.
MuSig2 combines the strengths of the two leading multi-signature designs without sacrificing trade-offs.
Bitcoin’s oldest multi-sig trick, the ‘CHECKMULTISIG’ OP-code, for instance, requires less communication from the signers of a multi-sig transaction but is less private than the MuSig1 multi-signature scheme, which improves user privacy at the expense of adding extra steps to the signing process.
Specifically, MuSig1 requires the parties in a multi-signature transaction to communicate in multiple rounds to approve a transaction.