- Fault proofs have gone live on the OP mainnet.
- The cryptographic proof system promises to usher the Optimistic ecosystem into a new stage of decentralization.
- Find out what these fault proofs are and why they are important.
L2Beat defines a Layer 2 chain as a solution that scales the base chain “in a trust minimized way.” But in reality, many so-called Layer 2 chains are still far from this ideal state, including Optimism, one of the largest Ethereum Layer 2 chains by TVL whose tech stack powers other big projects like Coinbase‘s Base.
The Layer 2 chain has recently taken a significant step towards reducing its reliance on trusted intermediaries with the rollout of fault proofs on its mainnet.
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What are these fault proofs, and why do they mark an important milestone in Optimism’s security and decentralization?
What are Fault Proofs?
On Monday, June 10, Optimism announced that fault proofs were now live on the OP mainnet after years of testing and development, bringing the network a step closer to complete decentralization.
Fault proofs are cryptographic proofs generated by verifiers (blockchain participants that check the validity of network transactions) when network operators try to pass incorrect transaction data from a Layer 2 network down to Ethereum. As such, they serve as a tool to prevent Ethereum Layer 2 chains from being dishonest.
Based on an optimistic worldview, fault proofs operate on the assumption that Layer 2 data is valid until proven otherwise during a “challenge period” that typically spans seven days. If a fault-proof is generated during this period, the flagged transactions are eliminated from the batch.
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How do these proofs bring the network and other Optimistic rollups closer to full decentralization?
Permissionless Withdrawals With Limited Training Wheels
The fault proof system unlocks permissionless ETH and ERC-20 token withdrawals for Optimistic rollups, meaning users can initiate these withdrawals without any involvement from a trusted third party. At the same time, it also means that users can be more involved in the system by participating as verifiers to challenge invalid withdrawals.
Before the advent of fault proofs, users were required to trust the network’s security council, a group charged with managing protocol upgrades, to submit accurate transaction data to the mainnet. This system exposed Optimistic rollups to complications from human error and bias.
With the advent of fault proofs, Optimism noted that the involvement of the security council in asset withdrawals was now limited to emergency interventions, retaining the power to revert the network to a permissioned system in the event of a system failure.
According to Optimism, with fault proofs and the security council safeguards, OP mainnet now satisfies the requirements of a stage 1 rollup as first defined by Ethereum co-founder Vitalik Buterin in November 2022, which is a rollup running fault or validity proofs with “limited training wheels.”
Optimism notes that in stage 2, the network will achieve complete decentralization and implement a multi-proof system.
Buterin celebrated Optimism’s Stage 1 rollup status in an X post on Tuesday, June 11.
“Welcome @optimism to the club of stage 1+ L2s! (meaning, L2s where the proof systems actually have teeth) I’m looking forward to seeing many more L2s join this club soon, especially some ZK ones,” he wrote.
On the Flipside
- Arbitrum, the largest Ethereum Layer 2 chain by TVL, has already had fault proofs for nearly two years.
- Blockchains built on Optimism’s OP Stack, like Base and World Chain, will still have to perform separate upgrades to rollout fault proofs.
- Validity proofs used by zero-knowledge-powered rollups are considered more decentralized and secure while offering a better user experience, as users do not have to wait seven days for their withdrawals to be processed.
Why This Matters
The OP mainnet and OP Stack-supported chains are some of the largest Ethereum Layer 2 chains by TVL. The introduction of fault proofs looks set to make these rollups more secure and decentralized.
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