比特币生态 Layer2 项目有哪些？一文汇总对比

翻译：白话区块链

目前，比特币第二层（L2）是这个问题最有前景的答案。本文比较了比特币L2与之前的努力，并讨论了一些最有前景的比特币L2项目。

1、保留无许可的比特币

2、构建比特币产品

1）L1应用程序

Ordinals 目前是在比特币上使用铭文发行 NFT 和 BRC-20 代币的标准。

2）比特虚拟机

BitVM 操作的简化图解

3）侧链

解决比特币的有限初始化性的另一种方法是利用侧链。侧链是完全初始化的独立区块链，例如与以太坊虚拟机（EVM）兼容，试图与比特币社区保持一致，并为该社区提供服务。Rootstock、Blockstream 的 Liquid 和 Stacks V1 是这些侧链的示例。

比特币侧链已经存在多年，通常在吸引比特币用户方面取得了有限的成功。例如，不到 4500 BTC 的流动性被桥接到侧链。然而，一些在这些链上构建的 DeFi 应用程序取得了一定的成功。例如，在 Rootstock 上的 Sovryn 和在 Stacks 上的 Alex。

比特币 L2

比特币 L2 正成为构建基于 BTC 的无许可应用程序的焦点。它们可以提供与侧链相同的优势，但具有继承比特币基础层的安全性保证。什么才是真正代表比特币 L2 的持续性在本文中，我们避免了这种争论，而是讨论了如何使 L2 与 L1 联系紧密，并讨论了一些有前景的 L2 项目的主要考虑因素。

3、比特币L2的要求

1）来自L1的安全性

比特币L2最重要的要求是从L1的安全性中获取其安全性。比特币是最安全的链，用户希望将安全性能延伸到L2。例如，闪电网络已经实现了这一点。

这就是为什么侧链被澄清为侧链的原因，它们有自己的安全性。例如，Stacks V1依赖于STX代币来确保其安全性。

在实践中，安全性要求很难实现。为了使 L1 安全地保护 L2，L1 需要能够执行某些计算以验证 L2 的行为。例如，以太坊的滚动从 L1 逐渐累积获取其安全性，因为以太坊 L1可以验证零知识证明（zk 滚动渐变）或验证零知识证明（乐观滚动渐变）。比特币基础层目前缺乏支持这些操作的计算能力。建议在比特币中添加新的操作码，以允许基础层验证通过限制连续提交的 ZKP。此外，诸如 BitVM 等提议试图实现在针对 L1 进行更改的情况下实施欺诈证明的方式。BitVM 的挑战导致欺诈证明的成本可能非常高（数百个 L1 交易），从而了其实际应用。

实现L1级别安全性的另一个要求是让L1具有L2交易的不可变记录。这被称为数据可用性（DA）要求。它允许仅监视L1链的观察者验证L2状态。通过铭文，可以将L2 TXs 的记录嵌入比特币 L1。然而，这引发了另一个问题，可以扩展性。比特币 L1 每 10 分钟 4MB 的块时间限制，数据吞吐量有限，大约大约 ~ 1.1 KB/s即使将 L2 交易高度压缩到约 10 字节/交易，假设所有 L1 交易都用于存储 L2 数据，L1 也只能支持约每秒 ~ 100 个交易的组合 L2 吞吐量。

2）从L1实现最小信任桥接

在以太坊的L2上，与L2的桥接由L1控制。桥接收L2，即转入，实际上意味着在L1上锁定资产，并在L2上铸造该资产的复制品。在以太坊中，这是通过L2本地桥接智能合约实现的。该智能合约存储所有桥接收L2的资产。智能合约的安全性来源于L1验证者。这使得桥接收L2的过程安全且最小化信任。

In Bitcoin, it is impossible to have a bridge that is collectively guaranteed by the entire L1 miners. Instead, the best option is to use a multi-signature wallet to store L2 assets. Therefore, the security of an L2 bridge depends on multi-signature security, i.e. the number of signers, their identities and how Peg-in and Peg-out operations are protected. One way to improve L2 bridge security is to use multiple multisigs instead of a single multisig that holds all L2 bridge assets. These include TBTC, where multisig signers must post collateral that can be slashed if they cheat. Likewise, the proposed BitVM bridge requires security deposits from multisig signers. However, in this multisig, any signer can initiate a Peg-out transaction. Peg-out interactions are protected by BitVM fraud proofs. If a signer behaves maliciously, other signers (verifiers) can submit fraud proofs on L1, resulting in slashing of the malicious signer.

4. Bitcoin L2 pattern

5. Main comparisons of Bitcoin L2 projects

1）Chainway

Chainway is building a zk rollup based on Bitcoin. Chainway rollup uses Bitcoin L1 as the data availability layer to store the rollup’s ZKP (zero-knowledge proof) and state differences. Additionally, this rollup exploits proof recursion so that each new proof aggregates the proofs issued on the previous L1 block. The proof also aggregates "forced transactions", which are L2-related transactions that force their inclusion on L2 by broadcasting on L1. This design has several advantages:

- By forcing transactions, ensures that Rollup's order generator cannot censor L2 transactions while giving users the right to include them by broadcasting them on L1.

- Using proofs recursively means that the prover of each block must verify the previous proof. This creates a chain of trust and guarantees that invalid proofs cannot be included on L1.

-The Chainway team also discussed using BitVM to ensure correct execution of proof verification and bridge transactions (peg-in/out). Using BitVM to verify bridged transactions reduces the trust assumption for bridged multisig to only an honest few.

2）Botanix

Botanix is ​​building an EVM L2 for Bitcoin. To improve consistency with Bitcoin, Botanix L2 uses Bitcoin as a PoS asset to achieve consensus. L2 validators receive fees from transactions executed on L2. Additionally, L2 stores the Merkle root of all L2 transactions on L1 using inscriptions. This provides partial security for L2 transactions, as the L2 transaction log cannot be changed, but data availability for these transactions is not guaranteed.

Botanix is ​​bridged from L1 via network processing on a decentralized multi-signature system called Spiderchain. Signers of a multi-signature are randomly selected from a set of arrangers. The orchestrator locks user funds on L1 and signs a statement to mint the corresponding amount of BTC on L2. Orchestrators are required to submit a security deposit to assume this role. Security deposits can be reduced in the event of malicious behavior.

Botanix has launched a public testnet, with the mainnet scheduled to launch in the first half of 2024.

3）Bison Network

Bison implements its Bitcoin L2 using a sovereign rollup style. It uses STARKs technology to implement zk rollup, and stores L2 transaction data and generated ZKP on L1 through Ordinals. Since Bitcoin cannot verify these proofs on L1, verification is delegated to users to verify ZKP on their devices.

For BTC bridging to/from L2, Bison uses Discreet Log contracts (DLC). Although the DLC is protected by L1, it relies on an external Oracle. This oracle reads the L2 state and passes the information to Bitcoin L1. If this oracle is centralized, it could maliciously spend assets locked on L1. Therefore, it is very important that Bison eventually plans to move to a decentralized DLC Oracle.

Bison also plans to support Rust-based zkVM. Currently, Bison OS implements many smart contracts, such as Token contracts, which can be verified using Bison prover.

4）Stacks V2

Stacks is one of the first projects focused on extending Bitcoin’s programmability. Stacks is being remodeled to better align with Bitcoin L1. This article focuses on the upcoming launch of Stacks V2 on the mainnet in April 2024. Stacks V2 implements two new concepts to improve alignment with L1. The first is the Nakamoto release, which updates the Stacks consensus to follow Bitcoin blocks and finality. The second is an improved BTC bridge called sBTC.

In Nakamoto’s release, blocks in Stacks were mined by miners who posted BTC collateral on L1. When Stacks miners create a block, these blocks will be pegged to Bitcoin L1 and receive confirmations from L1 PoW miners. When a block receives 150 L1 confirmations, the block is considered final and cannot be forked without forking Bitcoin L1. At this point, the Stacks miner who mined the block will be rewarded with STX and have their BTC collateral distributed to Stackers in the network. This way, any Stacks block older than 150 blocks (~1 day) relies on Bitcoin L1 security. For newer blocks ( 150 confirmations), the Stacks chain can only fork if 70% of Stackers support the fork.

Another Stacks upgrade is sBTC, which provides a more secure way to bridge BTC to Stacks. To bridge assets to Stacks, users deposit their BTC into an L1 address controlled by L2 Stackers. When the deposit transaction is confirmed, sBTC will be minted on L2. To ensure the security of bridged BTC, Stackers must lock up a deposit in STX that exceeds the value of the bridged BTC. Stackers are also responsible for executing peg-out requests from L2. Peg-out requests are broadcast as L1 transactions. Upon confirmation, Stackers burn sBTC on L2 and collaborate to sign an L1 transaction that releases the user’s BTC on L1. For this work, Stackers are rewarded with the previously discussed miner deposit. This mechanism is called Proof of Transfer (PoX).

Stacks aligns with Bitcoin by requiring that many important L2 transactions, such as miner PoX deposits, Peg-out transactions, etc., are performed on L1. This requirement does improve the alignment and security of bridging BTC, but may result in a degraded user experience due to L1’s volatility and high fees. Overall, the updated Stacks design resolves many of the issues in V1, but there are still some weaknesses. This includes the use of STX as a native asset in L2 as well as L2 data availability where only hashes of transaction and smart contract code are available on L1.

5）BOB

BOB（Build-on-Bitcoin）是一个旨在与比特币瞄准的以太坊L2。BOB在以太坊上作为一个乐观的滚动Rollup运行，并使用EVM执行环境来实现智能合约。

BOB初步接受不同类型的桥接BTC（WBTC、TBTC V2），但计划未来采用更安全的实体桥接，使用BitVM。

BOB的当前设计更好地描述为一条侧链，而不是比特币L2。这主要是因为BOB的安全性依赖于以太坊L1，而不是比特币的安全性。

6）SatoshiVM

其匿名性，该项目引发了很多争议。一些调查显示该项目与 Bool Network 有联系，目前是一个较早的比特币 L2 项目。

6、比特币L2范式中的创业机会

比特币 L2 领域提供了一些创业机会。除了构建最佳的比特币 L2 的环球的机会之外，还有其他一些创业机会。

1）比特币数据可用性层

2）MEV提取

3）比特币收益工具

7、总结

热点：比特币 特币 LAYER 项目