Optimism, one of the largest Ethereum Layer 2 chains by total value locked (TVL), has taken a significant step towards reducing its reliance on trusted intermediaries with the rollout of fault proofs on its mainnet. This cryptographic proof system promises to usher the Optimistic ecosystem into a new stage of decentralization, making it more secure and trustworthy for users.

Fault proofs are a crucial mechanism that prevents Ethereum Layer 2 chains from being dishonest by generating proofs when network operators try to pass incorrect transaction data from a Layer 2 network down to Ethereum. These 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.

The introduction of fault proofs on OP mainnet unlocks permissionless ETH and ERC-20 token withdrawals, meaning users can initiate these withdrawals without any involvement from a trusted third party. This is a significant improvement over the previous system, where users had to trust the network's security council to submit accurate transaction data to the mainnet, exposing the system to complications from human error and bias.

With fault proofs and the security council safeguards, OP mainnet now satisfies the requirements of a stage 1 rollup as defined by Ethereum co-founder Vitalik Buterin in November 2022. This means the rollup is running fault or validity proofs with "limited training wheels," and the network will eventually achieve complete decentralization in stage 2 by implementing a multi-proof system.

The OP mainnet and OP Stack-supported chains, such as Base and World Chain, 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, providing users with a more trustworthy platform for their transactions.

While Optimism has taken a significant step forward, it is important to note that Arbitrum, the largest Ethereum Layer 2 chain by TVL, has already had fault proofs for nearly two years. Additionally, blockchains built on Optimism's OP Stack will still have to perform separate upgrades to roll out fault proofs.

As the Layer 2 ecosystem continues to evolve, the adoption of fault proofs by Optimism and other rollups is a crucial milestone in ensuring the security and decentralization of the Ethereum network. This development will likely attract more users and projects to the Optimistic ecosystem, further strengthening its position in the Layer 2 space.