MuSig2 is an improved version of Musig1, which is a new signature scheme designed to enhance Multi-signature transactions.
Title: “What Is MuSig2?”
Author: Che Kohler
Compile: MK, MarsBit
As a BTC user, you use Digital Signature and specific messages to prove that you are the sender, which is your legitimate command as the owner of the Private Key. These Digital Signatures are used to show that you know the Private Key associated with the Address without exposing your Secret Key to the network.
There are several signature schemes for BTC, all of which are designed to perform different tasks. As the network matures and we use it in different ways, it is urgent to optimize the way these signatures are created.
With the launch of Taproot, Bitcoin continues to evolve, allowing developers to use these Soft Forks to build improved signature schemes for enhanced security, efficiency, and privacy for Satoshis. One recent development is Musig1 and its improved version MuSig2, which is a new signature scheme designed to enhance multisignature transactions.
What is BTC’s Multi-signature transaction?
When you send Bitcoin from one wallet to another, you typically use a single-signature transaction, as this is all you need to transfer funds.
And Multi-signature, commonly referred to as Multisig, refers to the authorization of BTC transactions requiring multiple Secret Keys. Distributed signatures are typically used to disperse responsibility for BTC ownership, but also for communication with second-layer solutions like the Lighting Network or Liquid Network.
The oldest Multi-signature technique for BTC is the “CHECKMULTISIG” OP-code, which can be used to create Wallets/transactions of this type. It requires less communication from signers of Multi-signature transactions than the MuSig1 Multi-signature scheme, but has poorer privacy. The latter improves user privacy at the cost of additional steps in the signing process.
What is MuSig1?
MuSig1 is a Multi-signature scheme that allows multiple parties to jointly sign a single message or transaction, requiring a certain number of signatures to authorize the transaction. This enhances security and provides additional control over funds. Compared to traditional script-based Multi-signature, MuSig uses less Block space, but as a trade-off, it requires more interaction between participants.
MuSig1 based on Schnorr signatures is a significant improvement over the traditional ECDSA-based Multi-signature scheme used in Bitcoin. It allows for Secret Key aggregation, which means a group of signers can create a single joint Public Key and generate a single signature for a transaction.
This process not only simplifies Multi-signature transactions, but also reduces the size of transactions, drop Money Laundering and improves privacy.
What is MuSig2?
MuSig2 is an upgraded version of MuSig1, which provides better security, efficiency, and privacy features. MuSig2, proposed by Blockstream researchers in November 2020, is a two-round multisignature scheme, which means that it only requires communication between two signers to create a valid signature.
This improvement makes MuSig2 more practical and user-friendly, as it drops the complexity of coordinating multiple signers.
What is the difference between MuSig1 and MuSig2?
The main difference between MuSig1 and MuSig2 lies in their communication rounds and security models:
Communication rounds
MuSig1 is a three-round multi-signature scheme that requires three rounds of communication steps to create a valid signature. In contrast, MuSig2 is a two-round scheme that allows signers to coordinate their actions faster and more conveniently.
Security Model
MuSig1 relies on the random Oracle Machine model (ROM) for its security proof, which assumes the existence of an ideal hash function. However, ROM is an idealized model that may not accurately represent real-world hash functions. On the other hand, the security proof of MuSig2 is based on the algebraic group model (AGM), which provides a more realistic representation of encryption primitives, thus offering stronger security guarantees.
What will MuSig2 bring to BTC?
The introduction of MuSig2 in BTC will bring several benefits, including:
Improve Efficiency
The two-round communication model of MuSig2 drops the complexity of coordinating multi-signature transactions, making it faster and more convenient for users.
Improve Privacy
Like MuSig1, MuSig2 allows Secret Key aggregation, which means that multi-signature transactions appear as regular single-signature transactions on the on-chain Block. This feature enhances privacy by making it more difficult for third parties to identify multi-signature transactions.
Greater Flexibility
MuSig2 supports more complex signing schemes, such as threshold signatures and hierarchical Secret Key structures, giving users greater control over their funds.
Better Security
The security proof of MuSig2 in AGM provides stronger security assurance than the ROM-based proof of MuSig1, providing a stronger foundation for multi-signature transactions.
What are the application scenarios of MuSig2?
MuSig2 is particularly advantageous for scenarios requiring enhanced security, privacy, and efficiency. For example:
Shared Custody
MuSig2 allows for longer secure management of shared funds, such as in trust or joint bank accounts, by requiring a certain number of signatures to authorize transactions. This feature drops the risk of a single point of failure and ensures that no single participant can unilaterally access the funds.
Cold Storage
MuSig2 can be used to create a multi-signature cold storage solution. As an individual, you may want to split access to your Wallet into multiple Secret Keys instead of just one Secret Key to access stored funds. This setup adds an additional layer of security as it drops the possibility of unauthorized access due to theft or loss of a Secret Key.
Privacy-Protected Wallet
A Wallet that prioritizes user privacy can implement MuSig2, creating multi-signature transactions that cannot be distinguished from regular single-signature transactions. This feature helps users maintain their privacy on-chain without sacrificing the security and control provided by multi-signature transactions.
Improvements to the second layer protocol
MuSig2 can be used in the second layer protocol, such as the Lightning Network, to protect off-chain transactions and improve their efficiency. Through aggregated signatures, MuSig2 reduces the on-chain footprint of second-layer transactions, thereby reducing the Money Laundering associated with opening and closing channels, reducing blockchain bloat, and making it more difficult for chain analysis companies to identify Lightning transactions from standard transactions.
MuSig2 will also help optimize the anchoring mechanism of the Liquid Network, making it cheaper and easier for federation members to manage their bridges. In addition, the Liquid Network also enables Taproot, allowing L-BTC users to use MuSig2 in production, so any innovation built on top of MuSig at the base layer can be replicated on the Liquid Network, and vice versa.
The improvement of MuSig is essential for Bitcoin.
MuSig2 is a promising development in the world of BTC, offering improved security, efficiency, and privacy features compared to its predecessor, MuSig1.
By simplifying multi-signature transactions and providing stronger security guarantees, MuSig2 has the potential to unlock new application scenarios and enhance existing ones, making BTC more accessible and secure for global users.
With the maturity and widespread application of technology, we can expect MuSig2 to play an important role in shaping the future of BTC and blockchain technology.
If you want to learn more about MuSig2 on BTC, you can use this article as a starting point, don’t completely believe what we say. Take the time to research other sources, you can start by checking out the following resources:
- BIP 0327
- MuSig2: Simple two-round Schnorr Multi-signature
- Bitcoin Ops – MuSig
- MuSig2: Simple two-round Schnorr Multi-signature
- MuSig1 Paper
- MuSig2 Paper
