Original author: Day
Original source: Vernacular blockchain
In the previous article, we introduced Bitcoin sidechains and UTXO+ client verification in Bitcoin Layer 2, and today we will introduce the remaining two, Roullp and Taproot Consensus.
01
Roullp
Originally a Layer 2 scalability solution on Ethereum to improve the performance and throughput of the blockchain network, Roullp reduces the burden on the main chain and improves overall performance by migrating most of the transaction data and computation off-chain, recording only the summary or summary information of transactions on the chain. The core idea of Roullp is to combine on-chain security with off-chain efficiency.
There are some challenges and limitations to implementing the Roullp scheme on Bitcoin. Bitcoin itself does not support smart contract verification, so the introduction of Roullp on Bitcoin requires other methods of verification, such as introducing client-side verification or building a self-built DA layer. As a result, the security of Bitcoin Layer 2 projects is highly dependent on client verification or self-built DA layers, rather than the security of Bitcoin itself.
Image source network, invasion and deletion
In addition, the native nature of Bitcoin does not match the essence of the Roullp solution, because the Roullp solution is mainly derived from Ethereum's layer 2 solution and is designed for Ethereum's characteristics. Bitcoin only plays a role in the storage of evidence and does not participate in the verification process, so it is somewhat different from the Roullp scheme in terms of intrinsity.
In addition, the Roullp solution also has challenges in terms of the degree of decentralization of Bitcoin Layer 2. This involves asset management and decentralization of the second layer of the ledger. At present, most of Ethereum's sequencer nodes are centralized and run by the Layer 2 project itself, which also makes the Bitcoin Layer 2 project face some problems in decentralization.
While it is technically feasible to implement Roullp on Bitcoin, it faces challenges in terms of Bitcoin's native nature, decentralization, and security. The current BTC Layer2 projects in the market also have varying degrees of flaws and limitations, so the development and widespread adoption of such projects still need to be further developed and verified. Let's talk about some of the representative projects:
- Merlin Chain
Merlin Chain is a Bitcoin Layer 2 solution that integrates the ZK Rollup network, decentralized oracles, and on-chain BTC fraud prevention modules. Merlin Chain's goal is to make the Bitcoin ecosystem more active by improving the efficiency and scalability of Bitcoin transactions. Merlin Chain uses ZK-Rollup technology to compress a large number of transaction proofs to improve transaction efficiency and scalability.
On Merlin Chain, the sequencer node is responsible for collecting and batching transactions and generating compressed transaction data, ZK state roots, and zkEVM proofs. The compressed transaction data and ZK proofs are then uploaded to Taproot on Layer 1 of Bitcoin via the decentralized Oracle network. Taproot is available as a public resource for the entire network to ensure transparency and security.
Although Merlin Chain has been criticized for its weak technology, it is the most popular BTC Layer2 in terms of ecology, community activity, and landing, with a current lock-up capital of more than $3.5 billion.
- B² Network
B² Network leverages the technology of zero-knowledge proofs and ZK Rollup to improve the performance and scalability of the Bitcoin network, and is compatible with Ethereum's smart contract functionality. The scheme records transaction data and proof of verification on the Bitcoin mainnet and ensures the correctness of the data through a challenge-response mechanism.
The architecture of B² Network consists of two main parts: the Rollup layer and the DA layer. In the Rollup layer, the user's transactions and associated proof of verification are processed and recorded, and the user's state is stored in this layer. These transaction and verification proofs are then transferred to the DA layer for storage and verification.
The DA layer includes decentralized storage, B² nodes, and the Bitcoin network. At this layer, a copy of the rollup data is stored permanently, and the verification proof is verified. However, since the Bitcoin mainnet itself cannot directly verify the data of the DA layer, B² Network has adopted a special approach where it writes the summary of the verification proof (Commitment) to the Bitcoin mainnet and sets up a time-locked challenge, similar to the OP's fraud proof.
One of the main problems with B² Network is that the Bitcoin mainnet cannot directly verify the data at the DA layer, so a challenge-response mechanism is needed to solve this problem, which may affect the decentralized nature and security of the system.
B² Network has recently strategically launched the B² Hub, which will provide services for other ZK Rollups, and provide data availability layer (DA) functions, and strategically cooperate with Babylon to realize the restaking and LSD functions of BTC Layer 2.
- Bison
Bison is a native Bitcoin-based ZK Rollup scheme designed to increase transaction speed and enable advanced features on the Bitcoin network. Developers can leverage ZK Rollup to build innovative DeFi solutions such as DEX/CEX, proxy services, and automated market makers. Unlike the Ethereum Virtual Machine (EVM) used by other Layer 2 solutions, Bison uses the Cario VM (the same as StarkNet) and is mainly built around the inscription ecosystem.
In terms of technical solutions, Bison is still essentially a sovereign rollup, which is verified by its own nodes. However, the DA (Dispute Assistant) only saves and publicizes the verification results in the form of inscriptions to the Bitcoin mainnet, and cannot fully inherit the value of Bitcoin.
Whether Bison can develop in the future can be said to be closely related to whether the inscription ecology can rise again.
02
Taproot Consensus
Taproot Consensus is a Layer 2 solution based on Bitcoin's native technology. It consists of three core components: Schnorr Signature, MAST Contract, and SPV Node Network.
Schnorr Signature is an efficient Bitcoin signature algorithm with better privacy protection, Schnorr Signature can expand the number of Bitcoin multisig addresses to 1000, and realize the decentralization of multisig addresses.
MAST Contract provides codification of multisig management, which does not rely on people to sign, but relies on code driven.
The SPV Node Network consists of Bitcoin light nodes, allowing users to conveniently and securely verify Bitcoin payments without having to save the full blockchain data.
Taproot Consensus relies on the consensus of the Bitcoin light node network to drive multi-signature, realizing decentralized Bitcoin cross-chain and management.
After flipping through the information, Taproot Consensus should be regarded as a new layer 2 track created by the BEVM project team itself, so it represents that the project is only themselves.
- Representative project: BEVM
BEVM is a BTC-based EVM-compatible Bitcoin Layer 2 with the goal of improving Bitcoin's scalability, reducing transaction fees, and fostering a more secure and decentralized financial ecosystem.
The core design of BEVM is based on the BTC Taproot upgrade in 2021, using the Musig2 aggregate signature algorithm to achieve decentralized BTC cross-chain, the Musig2 aggregate signature algorithm is brought by the Taproot upgrade, which can allow 1000 Bitcoin light node addresses to form a decentralized asset network, through which the transfer of BTC assets can be processed, so as to protect BTC Asset security on Layer 2: BEVM is fully compatible with EVM, and applications such as DeFi and GameFi that can run in the EVM ecosystem can be seamlessly migrated to Bitcoin Layer 2, and users can directly use BEVM ecosystem applications in mainstream crypto wallets (such as Metamask, OK Wallet, etc.).
At the end of last month, BEVM completed a financing of 10 million US dollars, with a post-investment valuation of 200 million.
03
brief summary
The above is the current progress of the mainstream project of Bitcoin Layer 2, and on the whole, it can be found that it is very similar to the development of Ethereum Layer 2, which is to solve the same problem, and introduce smart contracts on the basis of nativeness (security is linked to Bitcoin) and decentralization on Bitcoin, and in order to achieve the goal, there will be certain compromises made in some aspects.
In addition, there is another problem, that is, the current domestic and foreign institutions, the projects supported are not the same, the two sides do not buy each other, belong to their own state of playing, relatively speaking, relatively separated.