B²Network and Babylon join forces to create the most secure second layer and Bitcoin staking
BTC is currently the digital asset with the highest market capitalization, but the vast majority of it remains idle. Based on this, the Babylon team proposed the concept of BTC staking, allowing BTC holders to pledge their idle BTC to enhance the security of the PoS chain. The B² Network team proposes to build Bitcoin’s execution layer through modular design, allowing BTC holders to deposit BTC into Bitcoin’s execution layer (commonly referred to as Layer-2s) to perform various DApp operations, thereby increasing BTC of liquidity. B² Network and Babylon will work closely on this to build infrastructure and services that leverage Rollup as an execution layer protected by the Bitcoin network.
B² Hub, a core component of the B² Network, will enhance its security by integrating Babylon’s BTC staking. At the same time, B² Network also plans to integrate the BTC staking function in B² Rollup to support B² Rollup’s BTC LSD and BTC re-pledge scenarios.
B² Network’s modular design
Due to BTCs own storage and transaction load limitations, as well as Scripts non-Turing design, it cannot independently achieve network scalability.
To support Bitcoins scalability, B² Network adopts a modular blockchain design architecture.
We believe that a scalable blockchain network is divided into: execution layer, data availability layer and consensus layer. Among these three layers, the execution layer can achieve infinite horizontal expansion through the Rollup solution; the data availability layer implements DAS (data availability sampling) through B² Hub, combined with decentralized storage, and records the final data index and proof on Bitcoin, so this One layer can ensure the availability, security and decentralization of transactions and states in the execution layer; the consensus layer uniformly verifies the state transitions in the execution layer through commitment and challenge mechanisms, with sufficient security and decentralization.
The development of B² Network is divided into two stages:
The first phase started with B² Network running its own B² Rollup on B² Hub, running on Bitcoin through B² Hub, and completing the first Bitcoin ZK-Rollup running on B² Hub.
The second phase supports launching any ZK-Rollup on B² Hub, and completing the proof of data availability and state transition on Bitcoin through B² Hub.
Phase 1: B² Hub serves B² Rollup
The first stage of B² Network is divided into Rollup layer and DA layer.
The Rollup layer uses ZK-Rollup technology, and we are currently working with Polygon to build ZK-Rollup through zkEVM. In the Rollup layer, data and proofs are sent to the DA layer and consensus layer through Sequencer and Aggregator respectively.
B² Hub acts as the core hub, receiving data and proofs from ZK-Rollup. On the one hand, it stores the transactions and detailed data of the Rollup layer in the DAS protocol and distributed storage protocol of B² Hub, and writes the data proof into Tapscript and submits it to Bitcoin to ensure data availability; on the other hand, it verifies the ZK-Rollup The ZK proof generates commitments for the verification process and submits them to Bitcoin, allowing challengers to challenge based on these commitments and ultimately complete the verification of state transitions.
Phase 2: B² Hub serves multiple Rollups
The second phase of the B² Network will serve more ZK-Rollups through the B² Hub.
B² Hub will aggregate data submitted by different Rollups:
The transaction details and proofs of different Rollups will be stored in B² Hub’s DAS protocol and distributed storage protocol, then aggregated and finally submitted to Bitcoin.
ZK proof data from different Rollups will be recursively aggregated into a single ZK proof data through STARK, and after verification, a commitment submitted to Bitcoin will be generated to support the challenge.
BTC Staking on Babylon Protocol
Babylon is a scalable suite of Bitcoin security protocols designed to secure the decentralized economy. One such protocol is Babylon’s Bitcoin staking protocol. The protocol allows users to stake their BTC on the Bitcoin network. These staked BTC can then be used to secure other external networks, such as PoS systems. The staking process is trustless and non-custodial, meaning users do not need to transfer their Bitcoin to a third-party Bitcoin address, which is typically required by the Bitcoin Bridge protocol. Instead, users can keep their BTC remotely and autonomously, staking it to a Bitcoin script on the Bitcoin blockchain. These staked funds can be remotely penalized if any malicious behavior is detected. Babylons BTC staking is similar to ETH staking, but can secure other external networks such as PoS chains, making Babylons BTC staking similar to version 2.0 of Ethereums ETH staking, with functionality similar to Eigenlayers re-staking.
Excerpted from Babylon Bitcoin Staking White Paper
(https://docs.babylonchain.io/papers/btc_staking_litepaper(EN).pdf）
The process of Bitcoin stakers: (a) Optimistic case: Alice pledges, verifies the PoS chain, requests unbinding, and revokes the pledge within 3 days; (b) Non-optimistic case: Alice pledges, submits security violations to the PoS chain, Then her Bitcoins were destroyed.
Due to the non-Turing-complete design of Script on Bitcoin, it is impossible for anyone to provide proof of a security violation that is directly verifiable on Bitcoin. The Babylon Bitcoin staking protocol introduces a mechanism to deal with security breaches that prompt slicing to occur. The mechanism involves time-locking the staked Bitcoins and controlling the exposure of the secret key locking the Bitcoins whenever a staker or a delegated validator double-signs on the PoS chain (analogous to a double-spend). Babylon employs Extractable One-Time Signatures (EOTS) to enable accountable assertions, where using the same secret key to sign different blocks at the same height results in secret key disclosure. Babylon introduces an additional signing round after the base consensus protocol, called the final round. A block is considered final only when it receives EOTS signatures from more than 2/3 of the Bitcoins staked. In this round, all consensus security violations can be reduced to double signatures. If a security breach occurs in this modified protocol, some Bitcoin stakers have signed two blocks at the same height using EOTS. This resulted in the extraction of secret keys associated with these stakers. The EOTS signature scheme can be implemented via Schnorr signatures, which are natively supported in Bitcoin. Therefore, these extracted secret keys can be used to slice staked Bitcoins.
B² Hub is secured with Babylon
B² Hub is a PoS blockchain network that ensures the security of B² Hub through the verifiers of pledged assets (BTC and B² tokens), and ensures the data availability of Rollup and the validity of state transitions through the verifiers of B² Hub.
B² Hubs consensus mechanism requires an effective set of validators to conduct BFT consensus on blocks during an Epoch, including proposals and voting. Each block is then voted for EOTS by the final provider of staked Bitcoin through Babylons Bitcoin staking protocol. At the same time, in the B² Hub, the next Epoch will check the previous block, becoming a checkpoint through Babylon’s Bitcoin timestamp protocol. The final confirmation of a block in the B² Hub requires two checkpoints.
There are two confirmations for accessing B² Hub’s Rollup:
After passing the verification of B² Hub, Rollup completes the first confirmation;
B² Hub submits DA proof and state transition verification commitment to Bitcoin, and after the challenge period, Rollup completes the final confirmation.
B² Network makes B² Hubs consensus confirmation more secure through the Babylon Bitcoin staking protocol. Additionally, B² Network avoids long-range attacks through Babylon’s Bitcoin timestamping protocol.
Long-range attacks make the PoS chain impossible to cut and not secure enough. This attack is fundamental and cannot be addressed by modifying the consensus protocol unless there are additional sources of trust. To mitigate this threat, some PoS chains adopt a social consensus approach, in which stakeholders regularly make offline decisions on the correct block to the latest height and ignore other potential forks. However, this approach ties the security of the chain to the subjective opinions of participants. This approach is also known as weak subjectivity and violates the principle of decentralization. Additionally, because social consensus takes time, most PoS chains impose very long unstaking times, possibly as long as weeks.
To protect the PoS chain from long-range attacks, Babylon can use the PoS chains blocks as checkpoints for BTC and implement fork selection rules using earlier Bitcoin timestamps. This way, either the attacking fork will have a later timestamp in the Bitcoin canonical chain and will never be chosen by anyone, or in order to be chosen, the attacker will have to create a very long Bitcoin fork in which The attacking PoS fork has an earlier timestamp, which is economically impractical. Therefore, with BTC timestamps, long-range attacks are solved.
In B² Hub’s POS mechanism, a block needs to go through two checkpoints before final confirmation. Therefore, in B² Hub’s consensus mechanism, after passing the second checkpoint, we will submit the block information and the corresponding validator signature information to the finality provider. Finality providers are nodes that need to stake BTC and may be cut if they sign two blocks at the same height using EOTS. The finality provider then submits it to the B² Hub’s validators to collect finality votes. The verification node stores the collected finality voting signature information in a memory pool and broadcasts it to the lightweight client of B² Hub. Once 2/3 of the finality voting signatures are collected, the block on the B² Hub can be considered finalized.
Through Babylon Bitcoin staking and Bitcoin timestamps, B² Hub can effectively avoid long-range attacks and provide high security for different rollups.
B² Rollup supports Babylon Bitcoin staking
B² Rollup’s mainnet will support the BTC staking function.
B² Rollup’s BTC staking function will be divided into two stages:
Before the Babylon BTC staking mainnet is launched, B² Rollup will support users to use BTC to stake for B² Hub validators and receive B² token rewards.
After the Babylon BTC staking mainnet is launched, B² Rollup will transfer the BTC pledged by users on Bitcoin to a specific address to participate in Babylons BTC staking.
B² Rollup will support LSD-related projects to use BTC staking to conduct more DeFi activities, provide more liquidity for users participating in Babylon Bitcoin staking, and even conduct re-staking activities related to Bitcoin staking.
At the same time, Rollup will be able to leverage the infrastructure of Babylon and B² Network to ensure security through Bitcoin staking.
