Develop a smart contract where users lock their ETH until a specified timestamp. After this timestamp, any participants of the lottery can trigger the win() method and claim the reward (all locked ETH). The probability of being among the winners is proportional to the amount of ETH deposited.
Relying on any values that can be read during the execution of a smart contract is not secure. For example, using block.timestamp or block.difficulty to generate randomness is not secure because anyone can manipulate these values to their advantage.
The simplest solution for that would be to use Chainlink VRF (Verifiable Random Function) to generate a random number that can be used to determine the winner of the lottery.
To make the thing work without using Chainlink VRF, we can use a commit-reveal scheme. The idea is to have participants commit to a random number hash and then reveal the number. The lucky number is then calculated using revealed numbers.
To test the smart contract, you can use the following steps:
- Install dependencies:
yarn install- Run tests:
yarn test