MuSig2: New Advances in Bitcoin Multisignature

Bitcoin users prove they are the legitimate initiators of transactions through digital signatures and specific messages, without exposing their private keys. As the network evolves, optimizing these signature methods has become increasingly important. The introduction of Taproot provides developers with the opportunity to build improved signature schemes to enhance security, efficiency, and privacy. MuSig2 is such a new signature scheme designed to improve the performance of multisignature transactions.

Introduction to Bitcoin Multisignature Transactions

Unlike common single-signature transactions, multisignature transactions require multiple keys for authorization. This method is often used to decentralize Bitcoin ownership and is also applied in second-layer solutions like the Lightning Network. Early multisignature technology had lower communication requirements but poorer privacy. In contrast, the MuSig1 scheme enhances user privacy by increasing the signature steps.

Overview of MuSig1

MuSig1 is a multisignature scheme based on Schnorr signatures, which shows significant improvements compared to traditional ECDSA schemes. It supports key aggregation, allowing multiple signers to create a single joint public key and transaction signature. This not only simplifies multisignature transactions but also reduces transaction size, lowers fees, and enhances privacy.

Innovation of MuSig2

MuSig2 is an upgraded version of MuSig1, offering better security, efficiency, and privacy features. It is a two-round multisignature scheme that creates valid signatures with just two rounds of communication, significantly reducing the complexity of multi-party coordination.

The main differences between MuSig1 and MuSig2

1. Communication rounds: MuSig1 requires three rounds of communication, while MuSig2 only needs two rounds, improving efficiency.

2. Security Model: MuSig1 uses a Random Oracle Model (ROM), while MuSig2 adopts an Algebraic Group Model (AGM), which provides stronger security guarantees.

The Advantages of MuSig2 for Bitcoin

1. Improve efficiency: The two-round communication model simplifies the coordination process of multisignature transactions.

2. Enhanced privacy: Supports key aggregation, making multisignature transactions difficult to identify on the blockchain.

3. Greater flexibility: Supports more complex signature strategies, such as threshold signatures and hierarchical key structures.

4. Enhance Security: AGM-based security proof provides a more solid foundation for multisignature transactions.

Application Scenarios of MuSig2

1. Shared custody: Safely manage shared funds, such as trust or joint accounts.

2. Cold Storage: Create a multisignature cold storage solution to add an extra layer of security.

3. Privacy Protection Wallet: Achieve multisignature transactions that are difficult to distinguish from single-signature transactions.

4. Layer 2 Protocol Improvements: Optimize the off-chain transaction security and efficiency of Layer 2 solutions such as the Lightning Network.

The application of MuSig2 in the Liquid Network is also worth noting. The Liquid Network has enabled Taproot, allowing L-BTC users to utilize MuSig2 in production environments. This means that innovations based on MuSig can be mutually applied between the Liquid Network and the Bitcoin mainnet.

Conclusion

MuSig2, as an important advancement in the Bitcoin ecosystem, has made significant improvements in security, efficiency, and privacy. It simplifies the multisignature transaction process and enhances security guarantees, promising to open new application scenarios and optimize existing use cases. As the technology matures and is widely adopted, MuSig2 will play a key role in shaping the future of Bitcoin and blockchain technology.