The Solidity smart contract allows for community-based, decentralized lotteries to be arranged. Specifically, the lotteries are characterized by the following key features:
- Unpredictable, and non-manipulable randomness, based on the Commit-Reveal scheme, rather than block-dependant values.
- Absent fraud risks, thanks to the decentralized aspect of the lotteries, the manager has no exclusive control over lottery extraction and winner payment.
- Players involvement in the extraction, since players committed numbers are direclty used in the winner extraction.
- Automatic authentication through users' MetaMask crypto wallets.
Lotteries are divided into 3 phases:
- During the Commit phase, players choose a value they commit to, this value is secretly stored as a commitment, which corresponds to the SHA3-256 digest of the combination of the player's address + their chosen value + a salt for increased security. During this phase, players pay the entry fee to the lottery manager.
- In the Reveal phase, players have to reveal their chosen numbers. The new hash is still calculated from the revealed number + salt + the player's wallet address, which also acts as an authentication method. Note that only from now on a player can see other players' chosen values, and no new player can enter the lottery. The revealed values are verified thanks to the initial commitments, thus a player cannot cheat by revealing a different number. If a player reveals their number correctly, they will be added for the extraction phase.
- Finally, in the Extraction phase, the revealed values are summed together in a single value used for extraction as
val mod participants.length.
NOTE: Image released under the CC BY 4.0 License, please refer to this project's license for author attribution.
As briefly mentioned above, a player cannot input a specific value for the purpose of winning the lottery as other players' chosen values are only revealed when the Commit phase ends.
This means that the only way to purposely choose a number that leads to one's victory, would be to brute force the SHA3-256 digests and "crack" every players' number in a reasonable time, quite impossible.
- Node.js (tested on v20);
- Truffle suite (tested on 5.11.x);
- Ganache (tested on 2.7.x);
- Angular CLI (tested on 18.x).
Run the compile command inside the root folder of the project.
truffle compile
Run the migrate command inside the root folder of the project.
truffle migrate
Run the Angular serve command inside the src/ directory.
ng serve
The Front-end Angular DApp is rather minimal, and offers high compatibility with the Truffle suite thanks to the web3 library interfacing through the Factory contract.
Screenshots
This project is distributed under the MIT License.