A detailed explanation of Bitcoin's new generation of multi-signature scheme MuSig2
Original title: "What Is MuSig 2?》
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Original Author: Che Kohler
Original compilation: MK, MarsBit
As a Bitcoin user, you use a digital signature and a specific message to prove that you are the sender, which is your legal order 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 key to the network.
With the introduction of Taproot, Bitcoin continues to evolve, and developers can use these soft forks to build improved signature schemes that provide security, efficiency, and privacy for Satoshis. One of these recent developments is Musig 1 and its improved version MuSig 2, a new signature scheme designed to enhance multi-signature transactions.
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What are Bitcoin multi-signature transactions?
When you send bitcoins from one wallet to another, you're usually using a single-signature transaction because that's all you need to transfer funds.
Bitcoin's oldest multi-signature trick, the "CHECKMULTISIG" OP-code, can be used to create these types of wallets/transactions, it requires less communication from the multi-signature transaction signers, but is more private than the MuSig 1 multi-signature scheme Poor, the latter improves user privacy at the cost of adding an extra step to the signing process.
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What is MuSig 1?
MuSig 1 is a multi-signature scheme that allows multiple parties to co-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. MuSig uses less block space than traditional script-based multisig, but as a tradeoff, it requires more interaction between participants.
This process not only simplifies multi-signature transactions, but also reduces transaction size, lowers transaction fees and improves privacy.
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What is MuSig 2?
This improvement makes MuSig 2 more practical and user-friendly, as it reduces the complexity of coordinating multiple signers.
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The main difference between MuSig 1 and MuSig 2 is their communication rounds and security model:
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MuSig 1 is a three-round multi-signature scheme that requires three rounds of communication steps to create a valid signature. In contrast, MuSig 2 is a two-round scheme that makes it faster and easier for signers to coordinate their actions.
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MuSig 1 relies on a random oracle model (ROM) for its security proofs, which assumes the existence of an ideal hash function. However, ROM is an idealized model and may not accurately represent real-world hash functions. On the other hand, MuSig 2's security proof is based on the Algebraic Group Model (AGM), which provides a more realistic representation of cryptographic primitives and thus provides stronger security guarantees.
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Improve efficiency
MuSig 2's two-round communication model reduces the complexity of coordinating multi-signature transactions, making it faster and more convenient for users.
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Like MuSig 1, MuSig 2 allows key aggregation, which means that multi-signature transactions look like regular single-signature transactions on the blockchain. This feature improves privacy by making it harder for third parties to identify multi-signature transactions.
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better security
MuSig 2's security proof in AGM provides a stronger security guarantee than MuSig 1's ROM-based proof, providing a stronger foundation for multi-signature transactions.
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MuSig 2 is particularly beneficial for application scenarios that require enhanced security, privacy, and efficiency. For example:
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MuSig 2 allows multiple parties to securely manage shared funds, such as in trusts or joint bank accounts, by requiring a certain number of signatures to authorize transactions. This feature reduces the risk of a single point of failure and ensures that no single actor can unilaterally access funds.
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MuSig 2 can be used to create multi-signature cold storage solutions where you, as an individual, may wish to split your wallet access into multiple keys rather than a single key to access stored funds. This setup adds an extra layer of security because it reduces the possibility of unauthorized access due to key theft or loss.
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Wallets that prioritize user privacy can implement MuSig 2, creating multi-signature transactions that are indistinguishable from regular single-signature transactions. This feature helps users maintain their privacy on the blockchain without sacrificing the security and control provided by multi-signature transactions.
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Improvements to the second layer protocol
MuSig 2 can be used in second-layer protocols, such as the Lightning Network, to secure off-chain transactions and increase their efficiency. By aggregating signatures, MuSig 2 reduces the on-chain footprint of second-layer transactions, which reduces transaction fees for opening and closing channels, reduces blockchain bloat, and makes it harder for chain analysis companies to identify lightning from standard transactions trade.
MuSig 2 will also assist in optimizing the liquid network's anchoring mechanism, making it cheaper and easier for federation members to manage their bridges. Additionally, Liquid Network is also Taproot enabled, allowing users of L-BTC to use MuSig 2 in production, so any innovations built on top of MuSig at a fundamental level can be replicated on Liquid Network and vice versa.
MuSig improvements are essential for Bitcoin.
MuSig 2 is a promising development in the Bitcoin world, offering improved security, efficiency, and privacy features compared to its predecessor, MuSig 1.
By simplifying multi-signature transactions and providing stronger security guarantees, MuSig 2 has the potential to unlock new use cases and enhance existing ones, making Bitcoin more accessible and secure for users around the world.
As the technology matures and becomes widely available, we can expect MuSig 2 to play an important role in shaping the future of Bitcoin and blockchain technology.
