Arbitrum, the Ethereum layer-2 solution developed by Offchain Labs, has not experienced any fraud proofs since its mainnet launch in August 2021, according to Ed Felten, co-founder and chief scientist of Offchain Labs. The platform’s built-in security feature, known as interactive, multi-round fraud proofs, allows a layer-1 verifier contract to determine the validity of a challenger’s submission. If the submission is deemed valid, the fraudulent validator’s stake is slashed.
Fraud proofs are utilized when challenging validators suspect that another validator has assembled a batch of transactions incorrectly or fraudulently. However, despite the presence of this security mechanism, there have been no recorded instances of fraud-proof attempts on Arbitrum’s mainnet. In contrast, there were a couple of attempts on Ethereum’s proof-of-work (PoW) network when Arbitrum was running on the PoW fork. Fortunately, successful challenges were launched to defeat the attempted data theft.
Felten attributes the limited number of fraud-proof attempts on Arbitrum’s mainnet to the significant risk involved for malicious-intended validators. If another user notices the fraud and disputes the claim, the offending validator risks losing their entire stake. This strong disincentive prevents validators from attempting fraudulent actions on Arbitrum.
Currently, Arbitrum operates with a permissioned set of approximately 12 validators who participate in the fraud-proof game. However, Offchain Labs plans to introduce a new version of fraud proofs called the “BOLD” protocol (Bounded Liquidity Delay). Felten claims that this protocol will provide Arbitrum with faster guarantees for challenges. The current version allows adversaries to cause indefinite delays by sacrificing multiple stakes. However, the BOLD protocol ensures that adversaries will be defeated within approximately eight days, regardless of the number of stakes they sacrifice.
The BOLD protocol was introduced by Offchain Labs on August 4. It aims to enable permissionless validation for Arbitrum chains, potentially eliminating the need for a permissioned validation process and enhancing decentralization.
Felten also mentioned that Arbitrum’s fraud-proof feature will soon become permissionless, allowing anyone to participate in ensuring the correctness of the chain when challenges arise. This shift toward a permissionless model will further increase the platform’s decentralization and security measures.
The lack of fraud-proof attempts on Arbitrum’s mainnet demonstrates the effectiveness of its built-in security system and the strong disincentives for malicious validators. As the platform continues to evolve with the introduction of the BOLD protocol and the transition to a permissionless model, users can expect even greater security and decentralization in their interactions with Arbitrum.