Curve Block Oracle

https://curvefi.github.io/blockhash-oracle/

1. Overview

The Curve Block Oracle is a decentralized system for securely providing Ethereum mainnet block hashes and state roots to other blockchain networks. This enables permissionless storage proofs and cross-chain verification of Ethereum state, which is essential for a variety of use cases, including cross-chain governance, bridge security, and DeFi protocols.

The system is designed to be highly reliable and secure, leveraging a multi-committer consensus mechanism and LayerZero's cross-chain messaging protocol. It is currently deployed on over 20 EVM-compatible chains.

2. Key Features

• Permissionless Access: Anyone can use the oracle to verify Ethereum state on supported chains.
• Multi-Chain Support: Deployed across a wide range of EVM-compatible chains.
• Decentralized Security: Utilizes a multi-committer consensus mechanism with threshold validation to ensure the integrity of block data.
• LayerZero Integration: Leverages LayerZero for secure and efficient cross-chain messaging.
• Storage Proof Ready: Provides the necessary block hashes and state roots for Ethereum storage proofs.
• Resilient Design: The system is designed to be resilient to reorgs and other network disruptions.

3. System Architecture

The Curve Block Oracle consists of four main smart contracts:

1. MainnetBlockView (Ethereum only):

   • Address: 0xb10cface00696B1390875DB2a0113B3ab99752a4
   • Provides access to historical block hashes on the Ethereum mainnet.
   • To prevent reorg-related issues, it only returns hashes for blocks that are at least 65 blocks old.
   • This contract is called off-chain via LayerZero's lzRead functionality.

2. BlockOracle (All supported chains):

   • Address: 0xb10cface698eBbEeda6Fd1aC3e1687a8a3f5c5Df
   • Stores confirmed block hashes and decoded block headers.
   • Uses a threshold-based consensus mechanism to validate block data. Currently, the threshold is set to 1, with LZBlockRelay as the sole committer.
   • Once a block hash is confirmed, it is immutable.

3. LZBlockRelay (All supported chains):

   • Address: 0xfacefeed69e0eb9dB6Ad8Cb0883fC45Df7561Dc2
   • Handles cross-chain messaging via LayerZero.
   • Commits block hashes to the BlockOracle.
   • Supports read-enabled chains for direct queries to Ethereum.

4. HeaderVerifier (All supported chains):

   • Address: 0xb10CdEc0dE69a227307053bEbBFd80864B71ec27
   • Decodes RLP-encoded Ethereum block headers.
   • Extracts key information, such as the state root, parent hash, and other fields.

Data Flow

The process of retrieving and verifying a block hash is as follows:

1. Request: A user initiates a request for a block hash by calling the request_block_hash() function on a read-enabled chain's LZBlockRelay contract.
2. Read: LayerZero reads the requested block hash from the MainnetBlockView contract on the Ethereum mainnet.
3. Commit: The LZBlockRelay contract receives the response from LayerZero and commits the block hash to the BlockOracle.
4. Broadcast: The LZBlockRelay can optionally broadcast the block hash to other specified chains.
5. Verify: Once the block hash is confirmed, anyone can submit the RLP-encoded block header to the HeaderVerifier to extract the state root and other data.

4. Usage

For Developers

To use the block hashes for storage proofs, you can interact with the BlockOracle contract as follows:

// Get the confirmed block hash for a given block number
bytes32 blockHash = IBlockOracle(ORACLE_ADDRESS).get_block_hash(blockNumber);

// Get the state root for storage proofs
bytes32 stateRoot = IBlockOracle(ORACLE_ADDRESS).get_state_root(blockNumber);

Requesting Block Hashes

On read-enabled chains (such as Optimism, Arbitrum, and Base), you can request a block hash using the following steps:

# 1. Quote the required fees
read_fee = relay.quote_read_fee(read_gas_limit=200000, value=0)
broadcast_fees = relay.quote_broadcast_fees(target_chains, gas_limit=100000)

# 2. Request the block hash
relay.request_block_hash(
    target_chains,
    broadcast_fees,
    lz_receive_gas_limit=100000,
    read_gas_limit=200000,
    block_number=0,  # 0 indicates the latest safe block
    value=read_fee + sum(broadcast_fees)
)

Submitting Block Headers

Anyone can submit a block header for a confirmed block hash:

# Get the RLP-encoded header from an Ethereum node
encoded_header = eth.get_block(block_number).rawHeader

# Submit the header to the HeaderVerifier
verifier.submit_block_header(oracle_address, encoded_header)

5. Deployed Addresses

Ethereum Mainnet

• MainnetBlockView: 0xb10cface00696B1390875DB2a0113B3ab99752a4

All Other Chains

• BlockOracle: 0xb10cface698eBbEeda6Fd1aC3e1687a8a3f5c5Df
• LZBlockRelay: 0xfacefeed69e0eb9dB6Ad8Cb0883fC45Df7561Dc2
• HeaderVerifier: 0xb10CdEc0dE69a227307053bEbBFd80864B71ec27

Supported Chains

The Curve Block Oracle is deployed on the following chains:

• Ethereum
• Optimism
• XDC
• BSC
• Gnosis
• Polygon
• Sonic
• XLayer
• TAC
• Fantom
• Fraxtal
• Hyperliquid
• Moonbeam
• Kava
• Mantle
• Base
• Arbitrum
• Celo
• Avalanche
• Ink
• Plume
• Taiko
• Corn
• Aurora

6. Security Model

Trust Assumptions

• Curve DAO: The Curve DAO controls the ownership of the oracle and the management of committers.
• LayerZero: LayerZero is trusted for message delivery and the lzRead functionality.
• Threshold Security: The system requires a threshold of committers to agree on a block hash before it is confirmed.
• Chain Security: The overall security of the system is dependent on the security of the least secure supported chain.

Current Configuration

• Threshold: 1 committer (with LZBlockRelay as the sole committer).
• Read-Enabled Chains: Can query Ethereum directly.
• Non-Read-Enabled Chains: Rely on broadcasts from read-enabled chains.

7. Technical Details

Block Hash Constraints

• Minimum Age: 65 blocks (for reorg protection).
• Maximum Age: 8192 blocks (due to the EVM limit post-EIP-2935).
• Default: block.number - 65 for safety.

Gas Considerations

• Read Operations: Approximately 200,000 gas is recommended.
• Broadcast Receive: Approximately 100,000 gas per chain.
• Header Size: Headers must be under 1024 bytes.

RLP Header Decoding

The system extracts the following fields from the RLP-encoded block header:

• block_hash: The Keccak256 hash of the header.
• parent_hash: A reference to the previous block.
• state_root: The Merkle root for storage proofs.
• receipt_root: The root of the transaction receipt trie.
• block_number: The block height.
• timestamp: The block timestamp.

8. Example Use Cases

1. Cross-Chain Governance: Verify mainnet votes on L2s.
2. Bridge Security: Validate token locks on Ethereum.
3. State Synchronization: Prove account balances across different chains.
4. DeFi Protocols: Access mainnet price feeds on L2s.
5. Cross-Chain dApps: Build applications that utilize mainnet state.

9. Development

Prerequisites

• Python 3.12+
• uv

Setup

1. Clone the repository:

   git clone https://github.com/curvefi/blockhash-oracle.git
   cd blockhash-oracle

2. Install dependencies:

   uv sync

Running Tests

To run the test suite:

pytest

Deployment

The scripts/deployment directory contains scripts for deploying and configuring the contracts. The DeploymentManager.py class helps manage the deployment state across multiple sessions.

10. Resources

• Example Scripts: /scripts/deployment/
• Contract Source Code: /contracts/
• Security Audit: /report/

11. License

Copyright (c) Curve.Fi, 2025 - All Rights Reserved.