OP Mainnet

Website	optimism.io
Documentation	community.optimism.io
Explorer	optimistic.etherscan.io optimism.blockscout.com
Repository	github.com/ethereum-optimism/optimism
Social	optimism.mirror.xyz @OptimismFND @OPLabsPBC youtube.com twitch.tv/optimismpbc

Milestones

Fault Proof System is live on OP Goerli

2023 Oct 3rd

Fraud Proof system is live on Goerli.

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Mainnet migration to Bedrock

2023 Jun 6th

OP Mainnet, since Jun 2023 is running Bedrock.

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OP Stack Introduced

2022 Oct 17th

OP Stack, modular, open-sourced blueprint on how to build scalable blockchains.

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OP token airdrop

2022 May 31st

The first round of OP token airdrop.

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Mainnet for everyone

2021 Dec 16th

Whitelist got removed, there are no restrictions on who can transact with the network.

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OVM 2.0 is live

2021 Nov 12th

Network upgrade to OVM 2.0 and removal of fraud-proof system.

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Community Launch

2021 Aug 19th

All smart contracts allowed after prior approval.

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Mainnet Soft Launch

2021 Jan 16th

Only selected contracts like Synthetix and Uniswap are available.

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Description

Fraud proof system is currently under development. Users need to trust block Proposer to submit correct L1 state roots.

OP Mainnet is an EVM-equivalent Optimistic Rollup chain. It aims to be fast, simple, and secure. With the Nov 2021 upgrade to OVM 2.0 old fraud proof system has been disabled while the new fraud-proof system is being built (https://github.com/ethereum-optimism/cannon).

If you find something wrong on this page you can submit an issue or edit the information.

Risk analysis

Sequencer failureState validationData availabilityUpgradeabilityProposer failure

State validation

In development

Currently the system permits invalid state roots. More details in project overview.

Data availability

On chain

All of the data needed for proof construction is published on chain.

Upgradeability

Yes

The code that secures the system can be changed arbitrarily and without notice.

Sequencer failure

Self sequence

In the event of a sequencer failure, users can force transactions to be included in the project’s chain by sending them to L1. There is a 12h delay on this operation.

Proposer failure

Cannot withdraw

Only the whitelisted proposers can publish state roots on L1, so in the event of failure the withdrawals are frozen.

Rollup stage

OP Mainnet is a

Stage 0

Optimistic Rollup.

Learn more about Rollup stages

Please keep in mind that these stages do not reflect rollup security, this is an opinionated assessment of rollup maturity based on subjective criteria, created with a goal of incentivizing projects to push toward better decentralization. Each team may have taken different paths to achieve this goal.

Technology

Fraud proofs are in development

Ultimately, OP stack chains will use interactive fraud proofs to enforce state correctness. This feature is currently in development and the system permits invalid state roots.

Funds can be stolen if an invalid state root is submitted to the system (CRITICAL).

L2OutputOracle.sol#L141 - Etherscan source code, deleteL2Outputs function

All transaction data is recorded on chain

All executed transactions are submitted to an on chain smart contract. The execution of the rollup is based entirely on the submitted transactions, so anyone monitoring the contract can know the correct state of the rollup chain.

State derivation

Node software

The rollup node is composed of two software components: op-node, implementing consensus related logic, and op-geth, implementing execution logic. The configuration file for OP Mainnet can be found here.

Compression scheme

Data batches are compressed using the zlib algorithm with best compression level.

Genesis state

Since OP Mainnet has migrated from the OVM to Bedrock, a node must be synced using a data directory that can be found here. To reproduce the migration itself, see this guide.

Data format

The format specification of Sequencer’s data batches can be found here.

Operator

The system has a centralized operator

The operator is the only entity that can propose blocks. A live and trustworthy operator is vital to the health of the system.

MEV can be extracted if the operator exploits their centralized position and frontruns user transactions.

Users can force any transaction

Because the state of the system is based on transactions submitted on-chain and anyone can submit their transactions there it allows the users to circumvent censorship by interacting with the smart contract directly.

Withdrawals

Regular exit

The user initiates the withdrawal by submitting a regular transaction on this chain. When the block containing that transaction is finalized the funds become available for withdrawal on L1. The process of block finalization usually takes several days to complete. Finally the user submits an L1 transaction to claim the funds. This transaction requires a merkle proof.

Funds can be frozen if the centralized validator goes down. Users cannot produce blocks themselves and exiting the system requires new block production (CRITICAL).

Forced exit

If the user experiences censorship from the operator with regular exit they can submit their withdrawal requests directly on L1. The system is then obliged to service this request or halt all withdrawals, including forced withdrawals from L1 and regular withdrawals initated on L2. Once the force operation is submitted and if the request is serviced, the operation follows the flow of a regular exit.

Forced withdrawal from an OP Stack blockchain

Other considerations

EVM compatible smart contracts are supported

OP stack chains are pursuing the EVM Equivalence model. No changes to smart contracts are required regardless of the language they are written in, i.e. anything deployed on L1 can be deployed on L2.

Introducing EVM Equivalence

Permissions

The system uses the following set of permissioned addresses:

OptimismMultisig 0x9BA6…6b3A

This address is the owner of the following contracts: ProxyAdmin, SystemConfig. It is also designated as a Guardian of the OptimismPortal, meaning it can halt withdrawals, and as a Challenger for state roots. It can upgrade the bridge implementation potentially gaining access to all funds, and change the sequencer, state root proposer or any other system component (unlimited upgrade power). This is a Gnosis Safe with 5 / 7 threshold.

OptimismMultisig participants 0x42d2…9c64 0x3041…1623 0xE7dE…d02e 0xBF93…a2c8 0x4D01…6d15 0x7cB0…C54f 0x9bbF…31aa

Those are the participants of the OptimismMultisig.

ProxyAdmin 0x543b…fB04

Owner of AddressManager. Admin of OptimismPortal, SystemConfig, L2OutputOracle, L1StandardBridge.

Sequencer 0x6887…2985

Central actor allowed to commit L2 transactions to L1.

Proposer 0x4733…3A33

Central actor allowed to post new L2 state roots to L1.

Challenger 0x9BA6…6b3A

Central actor allowed to delete L2 state roots proposed by a Proposer.

Guardian 0x9BA6…6b3A

Central actor allowed to pause deposits and withdrawals.

Smart contracts

A diagram of the smart contract architecture

The system consists of the following smart contracts:

L2OutputOracle 0xdfe9…5a27 Implementation (Upgradable)Admin

The L2OutputOracle contract contains a list of proposed state roots which Proposers assert to be a result of block execution. Currently only the PROPOSER address can submit new state roots.