linea-monorepo/contracts/docs/workflows/operations/blobSubmissionAndFinalization.md

🧩 Blob Submission & Finalization

This document outlines the core data and finalization flows involved in LineaRollup's lifecycle, including blob commitment and zk-proof-based finality.

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📦 Blob Submission

This flow is used by the Data Submission Operator to submit blobs to the LineaRollup system.

🔄 Steps

1. Data Submission Operator calls submitBlobs() on the LineaRollup contract with 1 to N blobs, where N = network maximum.
2. For each submitted blob:
   • The contract verifies data integrity.
   • Performs evaluation checks via the point evaluation precompile.
   • Computes a shnarf for internal tracking.
3. The final computed shnarf is stored.
4. A corresponding event is emitted to reflect successful blob(s) storage.

Note: Shnarf denotes a generic and iterative hashing structure for a sequence of values. It is somewhat analog to a stack and supports efficient proof of append and proof of pop. The structure is similar to how block hashes are computed: for appends, newShnarf = H(oldShnarf || appendedValue). In Linea, the structure is used to encode the sequence of the submitted blobs.

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🧮 Finalization Submission

This flow finalizes 1 or more aggregated blob transaction submissions by verifying correct execution proven via zero-knowledge proofs.

🔄 Steps

1. Finalization Submission Operator calls finalizeBlocks().
2. LineaRollup contract:
   • Verifies submitted data matches the last finalized state and is non-empty to verify proper continuity.
   • Validates the messaging rolling hash feedback loop preventing manipulation or censorship.
   • Emits events for L2 blocks containing L2 → L1 messages.
   • Stores Merkle roots of L2 messages for proof-based claiming.
3. Computes the public input to be verified.
4. Calls the Plonk-based Verifier to validate the provided zk-proof.
5. Upon success, updates finalized state:
   • Includes latest
   • Stores the currentL2BlockNumber, finalStateRootHash and other related finalization state metadata.

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🔐 Verifier Contract

The verifier contract is an advanced zero-knowledge proof verifier specifically tailored for the PLONK protocol on Ethereum mainnet. It verifies zk-SNARK proofs generated using gnark, ensuring that a given proof corresponds to a valid computation without revealing inputs. The contract is written almost entirely in inline Yul assembly for gas efficiency and precision, and it uses elliptic curve operations, pairings, and the Fiat-Shamir heuristic to validate a serialized proof against public inputs. This is critical infrastructure for trustless, privacy-preserving applications such as rollups, where it ensures the integrity of off-chain computations before accepting their results on-chain.

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