Blockstream Reveals MuSig2; An Easy to Use Privacy-Focused 2-Round Schnorr Multisignature Scheme
As the Bitcoin Taproot upgrade approaches, a multi-signature solution is in development by Blockstream engineers, according to a medium blog post on Nov 4. Two engineers, Tim Ruffing and Jonas Nick said that they have already published a blueprint for MuSig2, an advanced version of the MuSig multi-signature scheme built to facilitate collective ownership of some Bitcoin and the creation of a single authorization signature.
Notably, Blockstream had debuted MuSig1 back in 2018 but is now seeking to solve communication shortcomings in the MuSig scheme's initial version. MuSig1 brought in a privacy aspect that previously did not exist in the CHECKMULTISIG code; this version also reduced the transaction fees. However, this particular version had implemented multiple backs and forth signing process; something that Musig2 is designed to solve.
MuSig2 Non-Interactivity Signature
As highlighted, this MuSig scheme version introduces a less interactive signing process; to be precise, only two communication rounds are required. The initiative, which is currently undergoing a peer review, is set for presentation at the Real World Crypto Conference scheduled for next year. Per the blog, MuSig2 leverages a non-interactive signing approach to enhance the utility in MuSig1. It reads,
“As the name suggests, MuSig2 is intended to be the successor of MuSig1.
It offers the same functionality and security as MuSig1 but makes it possible to eliminate almost all interaction between signers.”
Basically, MuSig2 combines the best of MuSig1 and CHECKMULTISIG functionalities to provide an ecosystem with both privacy and efficient communication. With the Taproot integration around the corner, Blockstream is set to update the Schnorr signature code library by replacing MuSig1 with MuSig2. The blog also hinted that they might test MuSig2 on Taproot code earlier, in preparation for deployment on the Bitcoin Mainnet.