Optimism is a Public Benefit Corporation (PBC) that created Optimistic Ethereum (O?), a leading Optimistic rollup on Ethereum. Optimism was formerly known as the Plasma Group, but has since changed its name and even raised funds from the likes of . The project aims to create a seamless L1-to-L2 developer experience by enabling (nearly) “copy and paste” code from one layer to the next thanks to its OVM. OVM stands for Optimistic Virtual Machine and is the virtual machine that executes all transactions in the rollup.
Otherwise, Optimism tries to stick as closely as possible to the Ethereum ecosystem. It uses a modified GETH for its Layer-2 node and has a Solidity compiler. However, it doesn’t support any EMV languages apart from Solidity. As mentioned, the Optimism team is working towards “EVM equivalence” with the next upgrade, Optimism 2.0, which enables the OVM to be equivalent to the EVM in all technical aspects.
Optimism is an independent blockchain that gets security guarantees from Ethereum. It’s compatible with EVM, meaning that smart contracts on Ethereum can easily be deployed on Optimism with only a few changes. Users can transfer assets between Ethereum and Optimism using bridges. If you’re using the official bridge, it can take around seven days to withdraw your assets from Optimism to Ethereum. If you use third-party bridges, you can withdraw your assets from Optimism to Ethereum within a few minutes by paying extra fees. For depositing assets on Optimism, you can use official or third-party bridges. Assets can be deposited within a few minutes using any bridge.
The sequencer is responsible for producing Layer 2 blocks. It gives users quick transaction confirmations and state updates. The sequencer builds and executes Layer 2 blocks and submits batches of compressed transactions to Layer 1. In addition to instant transaction confirmations and low gas fees, the Optimism’s user experience is significantly better than on Ethereum. Currently, only one sequencer is in operation, which the team behind Optimism manages. However, in the future, sequencing operations will be decentralized.
Optimism offers Ethereum Virtual Machine (EVM) equivalence. This EVM equivalence mitigates the need for a compiler and lets Optimism allow DeFi and NFT projects to “1-click deploy” to Optimism and, thereafter, still use all of the great Ethereum L1 tooling that’s available, e.g. Hardhat, Vyper, and more.
The EVM equivalence design philosophy is to produce an Optimistic rollup with ‘minimal difference’ to Ethereum. EVM equivalence extends the properties of Ethereum into the L2 as well. EVM-equivalent ORUs allow for the instant copy and pasting of codebases cross chains. Development and innovation on a single EVM-equivalent ORU are seamlessly transferable to any other EVM-equivalent ORU and to Ethereum itself. Since everything’s being developed on the EVM standard, the L1 network effects are extended to the L2s and innovations on an L2 reverberate back throughout the holistic ecosystem.
This also means developer tools, such as smart contract libraries, Hardhat, and Solidity tooling will work natively on OVM 2.0. Additionally, current dApps live on mainnet Ethereum can be ported over to the L2 with no changes necessary. Even better, Optimism can (eventually) reduce the Ethereum L1 gas fees for these same dApps by ~10,000% and increase the transactional throughput by ~200x.
Currently, fraud proofs are in development on Optimism and aren’t yet implemented. Optimism will use interactive fraud proofs to enforce the valid state of Layer 2.
Optimism’s upcoming Bedrock upgrade, a rollup client that offers Ethereum equivalence, is the most advanced rollup architecture. Its architecture is modular and extremely minimal, and with the implementation of Bedrock, Optimism will have client diversity. The Bedrock update is scheduled for Q1 2023.
Major changes to Optimism after the Bedrock upgrade include:
- two-second block time
- Time to deposit assets will be reduced to 2.5 minutes
- The difference between Ethereum’s Geth and Bedrock execution layer client will be only ~500 lines of code
- 20% reduction in the cost of posting data to Layer 1
- The EIP-1559 mechanism will determine layer 2 transaction fees
- Integration of EIP-4844
- Support for any proof system, including fraud proofs and validity proofs
In the future, a validity-proof system can be also built depending on the demand for a validity rollup. Currently, the Optimism team is currently building a fault proof calledCannon.”
Cannon is the world’s first EVM-equivalent fault-proof implementation. Its primary use case is allowing users to run an unaltered EVM on Layer 2 solutions with no sacrifices. To help achieve true EVM equivalence, Cannon leverages an existing EVM implementation known as GETH instead of re-implementing the EVM altogether.
Instead of executing the whole transaction on Layer 1, Cannon allows executing a single minigeth MIPS instruction on-chain. Minigeth uses a preimage oracle instead of geth’s state database. The use of preimage oracle allows fault-proof programs to access anything in Layer 1 or Layer 2.
Rollups post data on Layer 1, where they send transaction data, and the calldata’s hash is stored in the state. In case of a dispute, transaction data is required to solve the dispute using fraud proofs. Preimage offers an alternative way to access transaction data, i.e., by a Layer 1 block header itself. As no on-chain execution of transactions is required, transaction data can be posted as calldata to a Layer 1 account.
Optimism initially launched with a controlled rollout where a whitelisted group of dApps were approved to launch, most notably Uniswap, Synthetix, and 1inch. This limited release hampered early Optimism adoption as it had onboarded only six dApps compared to ~60 for Arbitrum. However, on December 16th, 2021, the Optimistic team removed the developer whitelist for a full, open system, allowing all dApps to begin building on Optimism if they so choose. Top projects, such as Tornado Cash, have already moved over. Now, let’s get into the inner details of Optimism’s working.
