Author: Margaux Nijkerk, CoinDesk; Translated by: Tao Zhu, Golden Finance
Optimism is a leading Layer 2 blockchain designed to help Ethereum users transact quickly and with low fees. Its technology is the basis for some of the biggest names in the blockchain space, including Coinbase exchange’s popular Base blockchain and Worldcoin’s World Chain (created by OpenAI founder Sam Altman).
But for years, there has been a problem with Optimism. All blockchains using Optimism technology are built on a core basic premise: they "borrow" Ethereum's security equipment. But in fact, this is not the case.
Until now, one core feature has been missing from Optimism’s security design: “proofs of failure.” On Monday, this long-promised technology finally landed on Optimism’s mainnet.
Fault proofs are designed to ensure the honesty of Optimism-based Layer-2 chains. They help prevent Layer-2 chain operators from passing inaccurate transaction data to Ethereum's Layer-1 transaction ledger and provide support for the Layer-2 chain's "decentralized" withdrawal mechanism.
All Layer 2 Rollup networks use similar “proof” technology, including Optimism’s competitor Arbitrum. It’s designed to ensure that Rollup users (whether NFT traders, retail investors, or well-known financial institutions) can trust Ethereum’s vast network of operators, rather than the Rollup’s own internal systems, to accurately record their transactions and withdrawals.
As Layer 2 chains like Arbitrum rolled out proof of stake for their systems, Optimism lagged behind. Over the years, this has made Optimism the target of criticism from peers who claim their technology is more secure and advanced.
Now that failure proofs are finally live on Optimism’s mainnet, the network’s developers — and a growing ecosystem of other teams using its technology — are hoping to put the past behind them.
How does “Proof of Failure” work?
Over the past two years, Layer 2 Rollup networks like Optimism have become the preferred method of running on the notoriously expensive Ethereum blockchain.
When a user submits a transaction to the Rollup network, it is bundled with other users’ transactions before being passed to Ethereum. These bundles are written to Ethereum’s transaction ledger at once, a setup that allows users to transact faster and at a fraction of the cost.
In theory, Rollup transactions are protected by "proofs," a cryptographic method that allows observers on Ethereum to check that transaction details are accurately recorded. This is most important in terms of withdrawals, allowing users to trust Ethereum (rather than the Rollup network) to withdraw their funds from the Layer 2 chain.
Without fault proofs, users who deposit funds into Optimism need to trust the rollup’s “security committee” to return the funds — a system that exposes the rollup to potential human error or bias. With fault proofs, these users only need to trust Ethereum.
Optimism, which gets its name from its “Optimism ” proof system, launched a version of the technology in its initial announcement in 2021 but quickly scrapped it after discovering problems.
“We literally ripped out the entire system, redesigned it, and rewrote the entire system,” OP Labs CEO Karl Floersch said in an interview. “It was brutal, but it was absolutely the right decision.”
The Optimism team previously shared in March that they were testing their error proof system on their Sepolia testnet. Since then, they have been audited by blockchain security firm Sherlock and found a number of bugs that they were able to patch.
“So we fixed all the issues that we found, and we feel pretty confident that it’s prime time for actual implementation,” Floersch said.
Starting this week, the network will once again rely on the error-proofing system to power withdrawals, but it will still retain the "training wheels" to ensure everything runs smoothly. The safety committee will remain intact and intervene if the error-proofing system fails. The combination of these two entities is what Optimism calls "phase one decentralization."
The goal is to eventually achieve Phase 2 decentralization, where the network will not have to rely on a security committee at all.
"The second stage is a multi-error-proof system that is sufficient to allow the system to operate in a certain way, such as autonomous driving. The safety board does not have the ability to intervene at the last minute," Floersch said.
Floersch added that the team is working toward Phase 2 goals, but he did not give a timeline for achieving that ultimate vision.
As fault proofs eventually make their way to Optimism’s mainnet, other blockchains using the Optimism OP Stack will also gain access to the technology. (According to DefiLlama, two blockchains currently using the Optimism OP Stack, Blast and Base, have surpassed Optimism’s mainnet in terms of total locked value.)
“We will start with the OP mainnet for this upgrade, which is a pretty big upgrade,” Floersch noted. “However, it shouldn’t take too long for Coinbase’s Base chain to implement the Proof of Failure system,” Floersch added.
