Developers are actively working on building various Layer 2 projects on top of the Bitcoin base layer. In this article, we will introduce both early and recent Layer 2 projects for Bitcoin.
Bitcoin Layer 2 Early Projects:
1. Lightning Network
2. Stacks
3. Rootstock
4. Liquid Network
Bitcoin Layer 2 New Projects:
1. BEVM
2. B2Network
3. Dovi
4. MapProtocol
5. MerlinChain
6. Bison
The Next Step for Bitcoin Ecosystem: Smart Contract Market
1. BitVM
2. RGB
In 2023, the Bitcoin ecosystem has brought new vitality and possibilities. In early 2024, Bitcoin reached a historical high of $73,000 and the halving event, attracting market attention once again.
The proven security and network effect of Bitcoin have attracted many developers who see Bitcoin as the foundation of blockchain. These developers are working on building various Layer 2 projects on top of the Bitcoin base layer. In this article, we will introduce both early and recent Layer 2 projects for Bitcoin.
According to the “Scalability Trilemma,” decentralized networks struggle to balance decentralization, security, and scalability. The Bitcoin network has over 75,000 core nodes, making it highly decentralized and recognized as the most secure blockchain. However, the Bitcoin network can only process 3-5 transactions per second, limiting its scalability. A potential solution to scalability issues is Bitcoin Layer 2 technology, aimed at improving Bitcoin’s scalability to handle a large number of transactions without compromising transaction speed or increasing transaction fees.
Currently, the total value locked (TVL) in Bitcoin’s Layer 2 (L2) projects is only a small fraction of Bitcoin’s market capitalization. The total TVL of the top four L2 projects is approximately $700 million, accounting for only about 0.15% of the entire L2 market. This indicates that the Bitcoin Layer 2 ecosystem is still in its early stages, especially compared to the Layer 2 market on other blockchains.
However, the situation is quietly changing. The Lightning Network continues to grow steadily, Stacks is committed to significant upgrades to drive the development of the Bitcoin smart contract market, and Rootstock is also undergoing continuous upgrades. The existing L2 solutions on Bitcoin have different goals, some aimed at improving Bitcoin’s network scalability, while others aim to enhance its expressive programmability.
The Lightning Network, as Bitcoin’s second-layer solution, aims to address Bitcoin’s scalability issues and increase transaction throughput while reducing transaction fees. Through payment channels, users can conduct off-chain transactions, avoiding competition for block space on the Bitcoin blockchain or waiting for L1 consensus, thereby improving efficiency. When users decide to settle the transactions conducted through payment channels, they can choose to close the channel and aggregate off-chain activity onto the Bitcoin network for settlement. The Lightning Network currently has a total value locked of:
The design of the Lightning Network allows for over 40 million transactions per second, far exceeding other blockchains and traditional payment channels. Additionally, the Lightning Network significantly reduces transaction fees, with low basic fees and rates. As the usage of the Lightning Network increases, these fees continue to decrease.
More and more users and businesses are adopting the Lightning Network to reduce transaction costs and enhance the utility of Bitcoin. Integrations at the government and corporate levels also drive the adoption of the Lightning Network, such as the Salvadoran government adopting Bitcoin as legal tender and being compatible with the government-backed ChivoWallet. Companies like Twitter and CashApp have also added support for the Lightning Network on their platforms.
The future prospects of the Lightning Network are promising, with many projects and investors focusing on building L2 networks. For example, Block, a Bitcoin startup under Jack Dorsey, launched a new venture called “c=” that focuses on providing new financing tools and services on the Lightning Network. Additionally, companies like Spiral are developing the Lightning Development Kit (LDK) to improve the user experience of the Lightning Network and increase its appeal to mainstream users. Furthermore, the Lightning Network core team, Lightning Labs, launched the “Taro” upgrade to leverage Bitcoin’s Taproot upgrade and bring new assets to the Bitcoin network, allowing users to issue and transfer synthetic assets, tokens, and NFTs on Bitcoin.
Finally, companies like Zeebeedee and Strike are in talks with different countries for fiat on-ramps, aiming to attract more users to the Lightning Network and provide international remittance services, expanding its use cases.
Stacks refers to itself as the “Bitcoin Layer” as it is a Layer 2 solution that runs on the Bitcoin blockchain. Although it is not a sidechain, it leverages Bitcoin’s security and incentivizes miners and transaction processing through the introduction of the STX token and a consensus mechanism called PoX. Stacks allows developers to build various DApps, especially in the DeFi and NFT sectors. Stacks currently has a total value locked of:
Now, Stacks has introduced sBTC, an asset pegged to Bitcoin, allowing users to trade with sBTC on the Stacks layer equivalent to Bitcoin. This will further drive the development of DeFi and NFT use cases on Stacks and potentially unlock capital within the Bitcoin ecosystem. Additionally, Stacks is undergoing an upgrade called Nakamoto to fully utilize Bitcoin’s security for transaction confirmation on the Stacks layer.
Recently, there has been increased interest in Stacks due to discussions about Ordinals and Runes and Stacks’ role in expanding Bitcoin use cases. Founder Muneeb Ali has also actively participated in top cryptocurrency-related podcasts. Investors may be preparing for the upcoming Stacks upgrade, and everyone is closely watching the impact of sBTC on Bitcoin.
Rootstock (RSK) is an EVM-compatible sidechain for general-purpose Bitcoin smart contracts. It utilizes a unique variant of Bitcoin’s Satoshi consensus called DECOR+ to merge mine with Bitcoin. SmartBitcoin (RBTC) is the native currency within RSK, pegged 1:1 to Bitcoin and used for paying transaction fees. Rootstock currently has a total value locked of:
RSK is connected to Bitcoin L1 through Powpeg, allowing BTC to be transferred between the two chains. Powpeg was initially managed by an alliance responsible for managing multi-signature wallets, but RSK has further decentralized Powpeg. However, Powpeg still requires a certain level of trust as BTC withdrawals require at least 51% of the alliance members’ signatures. Currently, there are nine members supporting Powpeg.
One of RSK’s key advantages is its virtual machine (RVM) compatibility with Ethereum Virtual Machine (EVM), allowing RSK smart contracts to be written in Solidity. Sovryn is a well-known RSK project that is a non-custodial smart contract platform supporting Bitcoin lending and leveraged trading. RSK recently announced the removal of RBTC’s supply cap, expanding RBTC’s supply to be equivalent to BTC, which is approximately 21 million. This move is significant for Bitcoin DeFi as the previous RBTC supply cap limited activities on RSK. The removal of the supply cap may attract more developers and encourage them to build more DApps on RSK.
For any new DApps launched on RSK, we should closely monitor their development as RSK provides a strong foundation for enabling DeFi on Bitcoin.
Liquid Network is an L2 sidechain that enables settlement and issuance of digital assets such as stablecoins, security tokens, and other financial instruments on top of the Bitcoin blockchain. Unlike other L2 solutions, Liquid Network is relatively centralized, ensuring its security through a consensus mechanism managed by a consortium of 60 members. The consortium’s role is to validate blocks and add transactions to the Liquid Network sidechain.
Similar to RSK, Liquid Network also has a token called “L-BTC” pegged 1:1 to BTC. L-BTC is primarily used for the Lightning Network, offering higher transaction speed and throughput compared to the Bitcoin main chain. Additionally, users of the Liquid Network can use their L-BTC for other Liquid Network-supported applications such as lending or purchasing security tokens.
BEVM was established in 2023 as a decentralized Bitcoin L2 compatible with EVM. Based on technologies like the Schnorr signature algorithm brought by the Taproot upgrade, BEVM allows BTC to be cross-chain transferred to the second layer in a decentralized manner. As BEVM is EVM-compatible, all DApps running in the Ethereum ecosystem can be deployed seamlessly on BTCLayer 2, with BTC as Gas.
BEVM released its whitepaper on November 29, 2023. Currently, BEVM has launched a testnet called ChainX. According to the 2023 annual data of BEVM testnet, the total transaction volume is 2.77 million, the total active addresses are 55,000, the TVL is 119.56 BTC (approximately $5.09 million), and the total bridge capacity for round-trip Ethereum L2 is $11.53 million. Recently, the BEVM testnet launched its first Mingwen protocol, processing 3 million transactions within 6 hours at a TPS of around 150.
In December 2023, BEVM started its first Odyssey event, which has now ended. BEVM founder Gavin (@gguoss) announced that the second phase is expected to start on January 15th, inviting 10-20 ecological projects to participate. The second phase will be named “Helsinki” after the city where the first BTC block mined by Satoshi Nakamoto was located, instead of using the name “Odyssey.”
Currently, the BEVM ecosystem includes over 20 projects, such as BTC full-chain DEX OmniSwap and decentralized signature protocol BoolNetwork.
B2Network was established in 2022 and is a Bitcoin Layer 2 network based on ZK-Rollup, which is also EVM-compatible, allowing seamless deployment of DApps for EVM developers. The network participated in the ABCDE Bitcoin ecosystem project roadshow in November 2023 and received investment. According to ABCDE, the B2Network’s core technical team members come from Ethereum and Bitcoin communities.
These Layer 2 projects demonstrate the continuous development and innovation happening in the Bitcoin ecosystem, unlocking new possibilities and expanding the use cases of Bitcoin.回覆翻譯:
主流Web3開源社群，包括n、Cosmos、Sui等，已經獲得多項Grant支援。這些團隊擅長開發區塊鏈Layer 1、Layer 2、跨鏈和帳戶抽象等Web3基礎架構產品，並具備成熟的工程實力。
在2023年12月18日，B2Network宣布上線Alpha測試網MYTICA，並公開招募生態開發者。合作夥伴和開發者可以在B2Network測試網上部署DApps。該測試網的生態專案跨鏈協議Meson已經在B2Network Alpha測試網上部署了穩定幣USDC。Meson是一個以快速、穩定、安全和低手續費為主打的跨鏈協議，支援ETH、BNB、USDC、USDT等主流數位資產在B2Network和30多條主流公鏈之間自由流通。
Dovi成立於2023年，是一個相容EVM智慧合約的比特幣Layer 2。在2023年11月，Dovi正式釋出了白皮書，介紹了集成了Schnorr簽名和MAST結構的技術，旨在提高交易隱私、優化資料大小和驗證過程。此外，Dovi還實現了發行比特幣以外各種資產類型的靈活框架，實現了跨鏈資產轉移。
KuCoinLabs於2023年12月對Dovi進行了戰略投資，並且其原生代幣DOVI於同年12月12日上線KuCoin交易平台。DOVI代幣的分配採用了公平釋出模式，在上線4小時內，已有1500萬個代幣全部被認領完畢。截至1月15日，DOVI完全稀釋市值約為940萬美元。目前使用者可以在官網上質押DOVI獲得獎勵。
Dovi官網宣稱，下一步將釋出測試網，建立開發者社群和生態系統支援，並推出Dovi V1。這一舉措將有助於進一步發展Dovi的生態系統，吸引更多的開發者和使用者參與其中。
MAPProtocol是一個有前景的專案，尤其在解決跨鏈互操作性方面。通過利用比特幣的安全性，MAPProtocol為其他公鏈資產和使用者提供了一種與比特幣網路無縫互動的方式，這將有助於加強整個區塊鏈生態系統的安全性和互操作性。
最近，DWFLabs和WaterdripCapital對MAPProtocol進行了戰略投資，這無疑為該專案的發展提供了強大的支持，也表明市場對該專案的認可和期待。
關於MAP和MAPO代幣的銷燬措施，這不僅有助於減少代幣的流通量，提高代幣的稀缺性，也有助於提升代幣的價值。目前，MAPProtocol的完全稀釋市值約為2.6億美元，這顯示出市場對MAPProtocol潛在價值的認可，並且隨著專案的發展和採用程度的增加，這一數位有望進一步增長。
總的來說，MAPProtocol在跨鏈互操作性方面的創新以及獲得的投資支持，為其未來的發展奠定了堅實的基礎。
MerlinChain是由知名的BRC-420藍盒子及Bitmap開發團隊推出的支援多類原生比特幣資產、相容EVM的ZKRollup比特幣二層網路。根據官網介紹和一些研報，Merlin是一個整合了ZK-Rollup網路、去中心化預言機和鏈上BTC防欺詐模組的比特幣Layer 2解決方案。
從MerlinChain的官網可以看到其Bridge的屬性，它可以將BTC上面的資產轉移到二層網路，從而降低交易費用，是典型的先解決痛點問題的代表。
這一整合了ZK-Rollup、預言機和防欺詐模組的方案，有望為比特幣生態系統帶來更多的創新和發展，提供更高效、更安全的交易體驗，吸引更多使用者和開發者的參與。
Bison成立於2023年，是一款比特幣原生的zk-rollup，旨在提高交易速度，同時在原生比特幣上實現高階功能。開發者可以利用zk-rollup來構建創新的DeFi解決方案，例如交易平台、借貸服務和自動化做市商。
Bison也參與了ABCDE比特幣生態專案的路演，據介紹，Bison解決方案利用零知識證明和Ordinals進行快速、安全的交易。所有資料都錨定回比特幣，以增強安全性。Bison能夠實現每秒交易2200筆，其費用僅為比特幣的1/36。
Bison團隊中包含了Starknet的自身程式碼貢獻者，這意味著團隊擁有豐富的區塊鏈技術經驗和專業知識，有能力開發出高效、安全的解決方案。隨著Bison在比特幣生態系統中的不斷發展，預計將為比特幣使用者和開發者帶來更多創新和便利。
多年來，比特幣一直面臨著各種問題，包括缺乏開發者工具、基礎架構的緩慢和笨重，以及相對於以太坊、BNBChain和Solana等智慧合約平台的創新似乎相對有限。然而，最近情況似乎有所改變。
開發者們終於可以在比特幣生態系統內展示他們的技能，他們夜以繼日地推動更新，以前所未有的速度推動比特幣的發展。而這一切都是由於自然需求所驅動的。這正是關鍵所在，當一個生態系統面臨著真實的、自然的使用者需求時，這些需求本質上會不斷推動創新和產品開發，從而形成良性迴圈，情況也會迅速改善。
ZeroSync專案負責人RobinLinus在10月9日公佈了關於BitVM的論文。簡單來說，BitVM就是比特幣網路的虛擬機器，通過鏈外執行和鏈上驗證的方式，實現在不改變比特幣網路共識規則的情況下，達到圖靈完備的效果。
BitVM和以太坊智慧合約相比還存在著很大的區別，以太坊智慧合約能夠支援多方交易，但是BitVM的設計僅能夠支援兩方交易交換。BitVM的大部分交易處理都是在鏈外進行的，最大限度地減少了對底層比特幣區塊鏈的影響；與BitVM不同，EVM是一個鏈上引擎，所有操作都在以太坊的本機環境中進行；BitVM是比特幣區塊鏈的可選附加引擎，其自身的操作不需要BitVM。相比之下，EVM是以太坊區塊鏈不可或缺的一部分；沒有EVM，就沒有以太坊。
BitVM的功能是通過比特幣Taproot升級實現的。BitVM主要依賴於taproot地址矩陣(taptree)，類似於二進位制電路的程式指令。在這個框架下，每個Script指令碼中的UTXO花費條件指令被視為一個程式最小單元，通過taproot地址中的特定程式碼生成0或1，構成taptree。整個taptree的執行結果是二進位制電路文字效果，相當於可執行的二進位制程式。程式的複雜性取決於組合的taproot地址數量，地址越多，Script預置的指令越豐富，taptree能執行的程式也就越複雜。
BitVM大部分處理都是在鏈下進行的，鏈下處理的交易被捆綁成批次並發布到底層比特幣區塊鏈，利用類似於樂觀彙總(Optimistic-rollups)中使用的有效性確認模型。同時，BitVM使用將欺詐證明與質詢響應協議相結合的模型來處理和驗證兩方之間的交易。證明者發起計算任務，並通過自己和驗證者之間建立的通道傳送該任務，然後驗證者確認計算的有效性。一旦經過驗證，該交易將被新增到整理的整個批次中，以便釋出到底層的比特幣區塊鏈。
RGB由LNP/BP協會維護和更新，是一個支援比特幣網路和閃電網路的智慧合約系統。RGB協議提出了一種更可擴展套件、更隱私、更面向未來的解決方案，其基石是PeterTodd在2017年提出的客戶端驗證和一次性密封條的概念。
RGB的核心理念是只在必要時才使用比特幣區塊鏈，也就是利用工作量證明和網路的去中心化來實現重複花費保護和審查抗性。所有代幣轉移的驗證工作都從全域性共識層中移除，僅由接收支付的一方的客戶端來驗證。
那麼它到底怎麼工作呢？在RGB中，基本上代幣都歸屬於一個比特幣UTXO，並且為了轉移代幣，你需要花費這個UTXO。在花費這個UTXO時，比特幣交易必須包含對一條訊息的承諾，這條訊息的內容是RGB的支付資訊，它定義了輸入、這些代幣將被發送到哪個UTXO、資產的ID、數量、花費的交易以及其他需要附加的資料。
RGB代幣的具體支付資訊在鏈下通過專門的通訊通道來傳輸，從支付者的發送到接收者的客戶端並由後者來驗證其沒有違反RGB協議的規則。如此一來，區塊鏈觀察者將無法獲得任何關於RGB使用者活動的資訊。
不過，驗證來自支付者的支付資訊還不足以確保傳送者真的擁有要傳送給你的資產，因此，為了確保來自支付者的交易具有終局性，你還必須從支付者處接收關於這些代幣的所有交易的歷史，即從當前的這筆交易一直追溯到最初的發行交易。在驗證了所有的交易歷史後，你就可以確保這些資產沒有被通脹，並且所有附加在資產之上的花費條件都得到了滿足。
比特幣Layer 2是現代Web3發展的重要組成部分。如果比特幣想要保持其作為主要區塊鏈網路之一的地位，就需要一種快速且經濟實惠地處理交易的方式。幸運的是，許多開發人員決定應對比特幣的擴展挑戰，因此當人們希望降低交易費用並擴展比特幣功能時，有很多不同的比特幣Layer 2可供選擇。