A library to implement arrng for verifiable rng in blockchain apps. aarng implements an oracle to serve signed randomness from random.org to a number of chains, including:
- mainnet
- arbitrum one
- optimism
- polygon
- eth goerli
- eth sepolia
- arbitrum goerli
- optimism goerli
- polygon mumbai
For more details please see https://www.arrng.io/.
$ npm install @arrng/contracts
An alternative to npm is to use the GitHub repository (arrng/arrng-contracts) to retrieve the contracts.
Once installed, you can use arrng by importing the consumer contract and passing in the arrng controller address to your constructor.
Please check https://www.arrng.io/ for the correct address for your chain.
pragma solidity ^0.8.0;
import "@arrng/contracts/ArrngConsumer.sol";
contract MyArrngConsumer is ArrngConsumer {
constructor(address arrngController_) ArrngConsumer(arrngController_) {
}
}
If you're new to smart contract development, we recommend heading to openzeppelin for a great guide to Developing Smart Contracts, to learn about creating a new project and compiling your contracts.
To request randomness from arrng (for example one number):
iD = arrngController.requestRandomWords {value: msg.value} (1);
The iD returned is a uint256 which uniquely identifies your request on that chain. You will need to send enough native token (e.g. ETH) for the response with the random number. This is served by api.arrng.io. See https://www.arrng.io/ for details.
The arrng oracle will wait for six confirmations before responding. To receive the response and use it in your contract you will need to include the fullfillRandomWords internal function.