Merkle Root Orders

Efficiently batch multiple programmatic orders using merkle trees for reduced gas costs.

Merkle Root Orders

Key Concept

Merkle root orders enable efficient batching of multiple programmatic orders through a single on-chain transaction. Rather than executing individual create() calls for each order, you establish one merkle root that authorizes all orders simultaneously — dramatically reducing gas costs.

Core Process

The implementation follows four main steps:

1. Collect orders as ConditionalOrderParams structures
2. Construct merkle tree where each leaf uses double hashing:
   keccak256(bytes.concat(keccak256(abi.encode(params))))
   
3. Register root on-chain via ComposableCoW.setRoot()
4. Validate orders by providing merkle proofs alongside order parameters

Critical Technical Details

Double Hashing Requirement

The system employs double hashing to prevent second preimage attacks. This is essential — always apply the following for leaf calculations:

keccak256(bytes.concat(keccak256(abi.encode(params))))

Proof Verification

When retrieving tradeable orders, you must supply the merkle proof. An empty proof array signals a single order rather than a merkle-authorized order.

Gas Efficiency

The overhead for setRoot() remains relatively constant regardless of tree size. For example:

Method	Gas for 50 orders
Individual create()	~2.5M gas
Merkle root setRoot()	~55k gas

This represents approximately a 45x improvement.

Context Storage

Use setRootWithContext() to store supplementary data (like timestamps) on-chain. For TWAP orders where t0=0, this allows automatic reading of start times from stored context.

Management Flexibility

• Updating orders requires recalculating the merkle root and invoking setRoot() again
• Setting the root to bytes32(0) invalidates all prior authorizations