Prover Contract

Overview

Polymer deploys the CrossL2ProverV2 contract (contract info), inspired by Superchain interop's CrossL2Inbox. Our implementation emphasizes on-chain proof validation with modified methods specifically designed to validate logs.

Core Validation Methods

Primary Method: validateEvent

Validate any event with a single call. For applications validating specific events emitted by their contracts on a given origin chain, this method provides a straightforward, plug-and-play solution.

validateEvent Function

function validateEvent(bytes calldata proof) 
    returns (
        uint32 chainId, 
        address emittingContract, 
        bytes memory topics, 
        bytes memory unindexedData
    )

⚙️ Function Behavior

Validates a cross-chain event from a counterparty chain and returns the event along with event identifiers. The function will revert if validation fails.

Parameters

Parameter	Type	Description
proof	bytes calldata	A byte payload containing the IAVL proof of the application's log stored in the Polymer Rollup, along with the Sequencer-attested state root and corresponding block height.

Return Values

Return Value	Type	Description
chainId	uint32	Chain ID of the emitting chain (identifier)
emittingContract	address	The contract which emitted the event (identifier)
topics	bytes memory	The topics array from the emitted event (indexed data)
unindexedData	bytes memory	The ABI-encoded event data for the matched log (unindexed data)

Advanced Inspection Methods

warning

These methods are optional and designed for applications requiring enhanced transparency and proof inspection capabilities.

These methods enable applications to:

• Perform static calls to examine proof contents
• Inspect origin chain transaction details
• Verify Sequencer-attested roots against public RPC endpoints
• Match proof components against API inputs

inspectLogIdentifier

inspectLogIdentifier

Inspect the origin transaction that a given proof corresponds to—useful for verification against API inputs.

inspectLogIdentifier Function

function inspectLogIdentifier(bytes calldata proof) 
    returns (
        uint32 srcChain, 
        uint64 blockNumber, 
        uint16 receiptIndex, 
        uint8 logIndex
    )

Parameters

Parameter	Type	Description
proof	bytes calldata	A byte payload containing the IAVL proof of the application's log stored in the Polymer Rollup, along with the Sequencer-attested state root and corresponding block height.

Return Values

Return Value	Type	Description
srcChain	uint32	Source chain that emitted the log
blockNumber	uint64	Block number on the source chain where the log was emitted
receiptIndex	uint16	Index of the transaction (receipt belongs to) in the array of all transactions in that block
logIndex	uint8	Index of the event in the logs array of the receipt (local to your transaction)

info

Note: logIndex is not the global log index—it's local to the specific transaction receipt.

inspectPolymerState

inspectPolymerState

Inspect the root and corresponding block height, enabling verification against the public RPC endpoint.

inspectPolymerState Function

function inspectPolymerState(bytes calldata proof) 
    returns (
        bytes32 stateRoot, 
        uint64 height, 
        bytes calldata signature
    )

Parameters

Parameter	Type	Description
proof	bytes calldata	A byte payload containing the IAVL proof of the application's log stored in the Polymer Rollup, along with the Sequencer-attested state root and corresponding block height.

Return Values

Return Value	Type	Description
stateRoot	bytes32	Represents the state of the Polymer Rollup, serving as the single source of truth
height	uint64	The block height corresponding to the state, used for querying the public RPC
signature	bytes calldata	The sequencer's attestation, committing to the root and its associated block height

tip

Verification: Use the returned height to query the public RPC and verify the stateRoot matches the on-chain state.