merkle batching

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title: Merkle Batching & Anchoring Convention created: 2026-07-07 updated: 2026-07-07 type: concept tags: [cryptography, layer-2] confidence: high source_files:

• docs/INTERFACE_CONTRACT.md

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Table of contents

• Overview

Overview

Batches of approved BCC commitments are anchored on-chain as a single Merkle root, verified by StateAnchor.sol in contracts.

• Hash function: keccak256 (not SHA-256) — cheap and native in the EVM, since the root is verified on-chain.
• Leaf: keccak256(abi.encodePacked(leafData)).
• Parent: sort the pair of child hashes ascending before concatenating — keccak256(a < b ? a,b : b,a) — the standard OpenZeppelin MerkleProof convention. This lets on-chain verification use MerkleProof.verify directly instead of a bespoke verifier.

This is the one hashing convention every package touching Merkle trees/proofs (contracts, integrity-oracle, bcc_middleware) must share exactly — a mismatch here silently breaks proof verification. See Interface Contract §4.4.