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Smart contracts

As an EVM-equivalent environment, Linea smart contracts can be written in any language that compiles to EVM bytecode.

The Linea stack includes onchain system contracts deployed on the finalization layer and on the Linea network itself, as well as auxiliary services that support network operations. Understanding these contracts and services is essential for operators managing deployments.

Finalization contract​

This contract is deployed to the finalization layer.

Purpose:
It enables secure interactions between Linea and the finalization layer.

Functionality:

  • Validates zk-SNARK proofs attesting to correct state transitions for batches of transactions
  • Records finalized state roots on the finalization layer
  • Acts as a canonical protocol contract for message passing between the Linea network and the finalization layer
  • Ensures messages execute only when the underlying zk-SNARK proof attests to correct state transitions
  • Anchors Linea state to Ethereum-level security guarantees
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In the Linea Public Mainnet deployment, this contract is referred to as the Linea Rollup and L1 Message Service. It provides rollup settlement and messaging functionality. Operators running private or hybrid networks may reuse the same contract pattern or deploy functionally equivalent contracts as part of their finalization design.

Native message bridge smart contract​

Purpose: Facilitates secure, proven communication of arbitrary messages and data between the finalization layer and the ZK-EVM.

Functionality:

  • Enables crosschain calls, instructing Linea to perform specific operations (minting, contract interaction, data relay)
  • Sends proofs or withdrawal requests back to the finalization layer
  • Supports functionality beyond token transfers

Native token bridge smart contract​

Purpose: Secure gateway for moving ETH and ERC-20 tokens to and from the finalization layer.

Functionality:

  • Uses non-custodial escrow, event tracking, and ZK-proof validation to guarantee trustlessness
  • Enables Linea to interoperate directly with Ethereum while preserving asset security

Deposit flow (finalization layer → Linea network):

  • Users send ETH or ERC-20 tokens to the Native Token Bridge contract on the finalization layer
  • Contract locks (escrows) these assets and emits an event
  • Once observed by the contract on the Linea network, an equivalent amount is minted or released to the user's account

Withdrawal flow (Linea network → finalization layer):

  • Users request withdrawal from the Linea network
  • Withdrawal is processed in a batch and proven valid using zk-SNARKs
  • Proof and withdrawal claim are submitted to the bridge contract on the finalization layer
  • Upon verification, the bridge contract unlocks and releases the withdrawn assets

Security:

  • Enforces strict verification rules (only proven withdrawals can be processed)
  • Replay and fraud protection through state roots, proofs, and event tracking across both layers
  • Maintains a registry of supported tokens and tracks total supply to ensure minted amounts never exceed locked amounts

Linea public network smart contract release​

Before each Linea Smart Contract release that targets the public network, the new version is prepared and tested. Testing includes static code analysis, formal verification is conducted where applicable, and documentation is updated.

Linea developers write in Solidity. Each Smart Contract is audited by 2-3 external auditors. Smart Contracts are deployed on target environments using production deployment keys and the auditors confirm the correct deployment of the contracts.

The Linea Operational Safe multisignature account and the Linea Security Council Safe multisignature account must both sign to upgrade the system.

Contract versioning​

For upgradeable contracts, the Linea adopts the OpenZeppelin Transparent Upgradeable Proxy pattern (v4.x). This pattern is used consistently across the platform’s core components, including but not limited to:

  • Core protocol contracts
  • Token Bridge contracts deployed on both Linea and Ethereum
  • Layer 2 Message Service

Next steps​