Deep Dive into B²Network's Mechanism: Will ZK+BitVM Become the Benchmark for Bitcoin Layer 2?
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Deep Dive into B²Network's Mechanism: Will ZK+BitVM Become the Benchmark for Bitcoin Layer 2?
Bitcoin's Layer 2 Rollup solutions possess considerable technical complexity and uniqueness.
Navigating Web3 tides with focused insightsAuthor: Haotian
From Ethereum's Plasma to Validium and then to mainstream Rollups, and from Bitcoin's sidechains to state channels and client-side validation, Layer2 solutions are fundamentally searching for a tradeoff framework that balances security, scalability, and decentralization.
With this in mind, I compare ZK-Rollup with the recently discussed @BsquaredNetwork approach, examining the technical differences and complexities of Bitcoin Layer2 from aspects such as DA implementation, interoperability, and security challenges.
For clearer comparative reference, we can loosely define a set of corresponding relationships:
ETH Plasma = BTC State Channels; ETH Validium = BTC Sidechains; ETH Rollup = BTC Client-Side Validation.
It’s clear that Ethereum’s Plasma corresponds to Bitcoin’s Lightning Network—both inherit BTC’s security but are currently limited by HTLC contracts to small-scale payments. Ethereum’s Validium maps to Bitcoin sidechains: highly scalable but lacking broad acceptance due to their independent consensus mechanisms. Ethereum’s Rollup, however, aligns best with Bitcoin’s client-side validation, achieving a balanced compromise among security, scalability, and decentralization—precisely why Rollup has become the dominant focus in Ethereum’s Layer2 landscape.
Following the logic of Ethereum’s ZK-Rollup, using Bitcoin’s client-side validation as a starting point, how should a Bitcoin Layer2 Rollup be constructed? Let’s explore this through the example of @BsquaredNetwork:
1) Client-Side Validation Component:
In a complete Ethereum ZK-Rollup, off-chain components include the Sequencer collecting and batching transactions, generating ZK-SNARK proofs and Merkle trees, then packaging and syncing them into the mainnet’s Calldata. Off-chain, the ZK-SNARK proof is verified via a Prover system, and the final state diff is uploaded to the mainnet. The mainnet then verifies data integrity and consistency using the state root and block data from Calldata, ultimately confirming finality.
Bsquare’s client-side component mainly consists of two layers: Rollup Layer and DA Layer. The Rollup Layer workflow is roughly as follows: the Sequencer collects and batches transactions, first synchronizing a copy to a decentralized storage environment. Then, a zkEVM generates a Proof, while transaction raw data, Merkle trees, Bitcoin state, and other information are aggregated into a combined Proof and synced to B² nodes in the DA Layer.
Two key differences emerge here. First, Bitcoin requires original TX data to be synchronized to a decentralized storage environment, whereas ZK-Rollup assumes local storage by default. Second, Ethereum can directly sync data to the mainnet’s Calldata, but Bitcoin’s mainnet has limited storage capacity and lacks verification capabilities. Therefore, Bsquare routes this data to B² nodes operating in a client-side environment.
2) Data Availability (DA) Component
In Ethereum, the mainnet provides DA capability for Rollups—the purpose of syncing data to Calldata is precisely to leverage the mainnet’s DA verification. Since Bitcoin’s mainnet lacks such verification ability, DA functionality must be fulfilled by a DA Layer built within the client-side environment.
After receiving aggregated Rollup data, B² nodes perform circuit compilation, compressing the data and uploading it to the Bitcoin mainnet in the form of Inscription engravings. At the same time, B² nodes run a Prover system to perform decentralized verification of ZK proofs, generating a Bitcoin Commitment. This commitment, along with Rollup data and other aggregated information, is also inscribed into the blockchain as an inscription.
This raises two questions:
1. Why not use third-party DA solutions like Celestia, but instead build their own? This decision stems from the unique nature of the Bitcoin ecosystem. B² nodes require an indexer to perform decentralized parsing and indexing of inscriptions on the Bitcoin mainnet. Additionally, ZK Proofs must be uploaded to the mainnet in the form of Commitments. During inscription, data must undergo circuit pre-compilation and compression to minimize storage footprint on the mainnet.
2. If DA is not provided by the mainnet, why upload various Rollup data to the mainnet as inscriptions? This ensures an immutable transaction record on the mainnet, providing a foundation for future challenge processes.
3) Challenge Mechanism
In ZK-Rollup, the mainnet Rollup contract can re-verify transaction integrity and consistency using packed data from Calldata and the state diff submitted by the Prover—this is possible thanks to the mainnet’s verification capability and the advantages of ZK technology.
However, in a Bitcoin Rollup environment, the mainnet lacks native verification ability. The value of ZK technology here lies primarily in SNARKs’ ability to compress data succinctly while ensuring consistency. But if the Sequencer falsifies data during off-chain transaction collection, the entire chain becomes compromised—and finality confirmation cannot reject fraudulent data. Thus, a mechanism must be designed to challenge such "fraudulent" behavior.
How can this be achieved? Revisiting my earlier article on BitVM, you’ll recall that BitVM is a theoretical framework enabling Turing-complete computation on Bitcoin. However, its method of transmitting precompiled circuits via Taproot Trees to the Bitcoin mainnet incurs prohibitively high miner fees, making it impractical. Yet, borrowing BitVM’s logical structure to design a challenge mechanism presents a viable alternative.
The challenge mechanism locks BTC in a UTXO on the mainnet. When a user launches a challenge against the Layer2 chain in BitVM format, they can claim the BTC previously locked on the Bitcoin mainnet. The engraved inscriptions on the Bitcoin mainnet, along with publicly accessible raw data, Merkle trees, Commitments, and B² nodes’ records, serve as evidence for initiating challenges. If a challenge proves inconsistencies between the data in B² nodes and the inscribed inscription data on the mainnet, the offending B² node not only loses its staked BTC in the UTXO but must also roll back transactions and re-sync indexers and historical data.
In summary,
Bitcoin’s Layer2 Rollup solutions exhibit significant technical complexity and uniqueness:
For instance, the client-side validation process must retain all data generated by the Sequencer via decentralized storage to ensure traceability;
The DA layer must construct an off-chain decentralized data verification system, using Commitments and inscription engraving to guarantee consistency of DA data;
Even with ZK technology, a transparent challenge mechanism is still required to ensure security. The entire process must strike a fair balance between decentralization, security, and scalability.
The emerging blueprint is evident: since the Bitcoin mainnet cannot provide verification or DA, leverage inscriptions to etch limited DA onto the mainnet, paired with a Turing-complete challenge system based on BitVM circuits—achieving Rollup chain transparency and security. Using ZK technology combined with a BitVM-based challenge system to compensate for Bitcoin’s lack of DA and verification capabilities.
If even Ethereum Rollups still face governance risks—such as upgradable multi-sig Rollup contracts—and cannot guarantee 100% security, what users truly trust is a relatively transparent and open contract interaction mechanism. So now, although we cannot achieve absolute BTC-consensus-level security, we are presented with a transparent, open challenge mechanism based on BitVM. Despite far greater technical complexity, the logic appears sound. In conclusion, if this paradigm—ZK technology + client-side validation + DA inscription + BitVM challenge—gradually gains market acceptance, could it become the new benchmark for Bitcoin Layer2 Rollups?
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Haotian | CryptoInsight
