Offchain Labs Launches BoLD, a Permissionless Validation Protocol for Arbitrum on Ethereum
Offchain Labs, the team behind the innovative Arbitrum project, has unveiled their latest creation: BOLD (Bounded Liquidity Delay). This revolutionary dispute protocol has the potential to enable permissionless validation for Arbitrum chains, bringing greater decentralization and security to the platform. The unveiling of BOLD marks a critical milestone in the ongoing quest to enhance the capabilities of Optimistic Rollup chains and settle states more efficiently.
Arbitrum’s existing validation process for fraud proofs relies on a group of validators posting claims about the L2 state they have verified to be true on Ethereum. These claims undergo a 7-day dispute resolution process, during which other validators can challenge the assertions. Once confirmed, the L2 state is considered accurate on Ethereum, allowing assets to be bridged between Arbitrum chains and Ethereum L1. However, this validation process is currently permissioned and susceptible to denial-of-service attacks, as malicious validators can repeatedly spend funds to delay withdrawals from L2 to L1.

Enter BOLD, the brainchild of Offchain Labs’ ingenious team. The protocol introduces a fixed, upper bound of 7 days on confirmation delays without falling prey to delay attacks. This groundbreaking approach takes validation to a new level of safety and permissionless participation, significantly advancing the decentralization of Arbitrum chains.
The power of BOLD lies in its ability to support efficient all-versus-all disputes, guaranteeing fixed upper bounds on confirmation times for Optimistic Rollups’ settlement. Furthermore, BOLD ensures that a single honest party can prevail against any number of malicious claims, making it incredibly resilient against attacks.
One key distinction that sets BOLD apart is that disputes are not tied to specific validators or entities but to the deterministic execution of an L2 state. This means that anyone in agreement with a state can defend it until a single point of disagreement is identified. With the honest L2 state being deterministic, honest participants will always emerge victorious, as malevolent actors cannot fabricate proofs of execution.
To allow the community to delve deeper into the inner workings of BOLD, Offchain Labs has released the code and research specification on Github. The implementation includes a comprehensive challenge manager that can post assertions about an L2 state and actively participate in challenges against multiple malicious adversaries, ultimately confirming the correct state.
To bolster the credibility and security of BOLD, the protocol has undergone a meticulous audit by Trail of Bits, and the audit report is included in the Github repository. Additionally, Offchain Labs’ dedication to transparency is evident in their decision to adopt the same licensing as Arbitrum Nitro, making the codebase easily accessible for integration into various Arbitrum technology chains.
The team at Offchain Labs is keenly aware that understanding the intricacies of such a sophisticated system is crucial. Therefore, they are actively working on building a Challenge visualizer and API, which will provide valuable insights and understanding to the community.
As for the future of BOLD, the roadmap includes sharing instructions for running an Arbitrum Nitro devnet with BOLD challenges enabled in the coming weeks, publishing formal proofs code written in the Isabelle programming language, and a public testnet environment for community participation in challenge games. Based on the community’s response and feedback, Offchain Labs plans to prepare an AIP (Arbitrum Improvement Proposal) for the DAO to decide whether to adopt this new challenge protocol in Arbitrum One and Nova.
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