2022-01-07-on-chain-randomness.md

title	description	slug	authors	tags	image	hide_table_of_contents
Use onchain randomness	How to use onchain randomness in your smart contracts.	/developer-guide/start/randomness	name title url image_url Josh Crites Developer Relations, cLabs https://github.com/critesjosh https://github.com/critesjosh.png	solidity randomness oracle	https://dl.airtable.com/.attachmentThumbnails/a7e530eb72ac8f30f37c0a3447ef0e7d/72e944da	false

import PageRef from '@components/PageRef';

Onchain randomness is used for selecting validators to perform phone number verification. Read more about how onchain randomness is produced at the provided page.

This randomness can be used by any smart contracts deployed to a Celo network.

import "celo-monorepo/packages/protocol/identity/interfaces/IRandom.sol";
import "celo-monorepo/packages/protocol/common/interfaces/IRegistry.sol";

contract Example {
    function test() external view returns (bytes32 randomness) {
        randomness = IRandom(
            IRegistry(0x000000000000000000000000000000000000ce10)
                .getAddressFor(keccak256(abi.encodePacked("Random")))
        ).random();
    }
}

Alternatively, through inheritance of UsingRegistry.

import "celo-monorepo/packages/protocol/common/UsingRegistryV2.sol";

contract Example is UsingRegistryV2 {
    function test() external view returns (bytes32 randomness) {
        randomness = getRandom().random();
    }
}