Implement in Your Contract

The process is similar to Chainlink VRF, but simpler.

Overview

This guide provides a step-by-step approach to implementing L1 VRF (Verifiable Random Function) on BitcoinL1. For the full implementation details, refer to the GitHub repository.

Prerequisites

• Solidity development environment

• Foundry/Forge for development and testing

• Wrapped Bitcoin (WBTC) for fees

Key Implementation Steps

1. Set Up Your Consumer Contract

• Inherit from VRFConsumerBaseV2

• Define critical VRF parameters:

  uint8 private constant NUM_WORDS = 1; // Currently supports 1 random numberu
  int16 private _requestConfirmations = 2;
  uint32 private constant CALLBACK_GAS_LIMIT = 1500000;
  uint64 private constant SUB_ID = 0;
  bytes32 private constant KEY_HASH = 0x787d74caea10b2b357790d5b5247c2f63d1d91572a9846f780606e4d953677ae;
  address coordinatorAddress = 0x6868BdCA28c4731aada101945Ea83D0854eFBb29;

2. Implement Required Functions

• Constructor initializing VRFConsumerBaseV2

• fulfillRandomWords() method to process random numbers

• Utility functions for managing requests:

  function getRequestConfirmations() public view returns (uint16);
  function setRequestConfirmations(uint16 requestConfirmations) public onlyOwner;
  function setCoordinator(address newCoordinator) public onlyOwner;

3. Subscription and Fee Management

• Set up a subscription address

• Ensure address has sufficient WBTC

• Set allowance for coordinator

• Be prepared to pay 0.000005 BTC per random number request

Randomness Request Flow

1. Call requestRandomWord(VRFV2PlusClient.RandomWordsRequest calldata req)

2. Coordinator collects fee (0.000005 BTC in WBTC)

3. Fulfillment service calls fulfillRandomWords()

4. Process random number in your contract

Security Considerations

• Validate all inputs

• Maintain WBTC balance

• Monitor gas costs

• Handle edge cases carefully

Development Setup

forge install openzeppelin/openzeppelin-contracts --no-commit
forge install smartcontractkit/chainlink --no-commit

Additional Resources

• Full Repository
• Chainlink VRF Documentation (for reference, not really needed for L1 VRF)
• Foundry Documentation