toss-up

Fully decentralized betting platform using Chainlink VRF, Ethereum Smartcontracts, Interplanetary FileSystem & React frontend. The betting system is powered by Ethereum Smartcontracts for transparency & immutability. Application assets are stored on the Interplanetary FileSystem (IPFS) for censorship resistance and maximum distribution. The Chainlink Network is used by the TossUp Smartcontract as an oricle to generate randomness and determine ETH and Wei to USD price at the time of transaction.

Issues

• Initialize React App & Setup
• Deploy Smartcontract to Rinkeby
• React/Web3 Components
• Stylize & Test
• Make Readme & Test with Jest
• WalletConnect & Deploy to IPFS

Table of Contents

• Ethereum
• IPFS
• Chainlink
• Requirements
• Installation
• Usage
• Demo
• Questions
• License

Application Preview

Ethereum

TossUp's Smartcontract is deployed live on the Ethereum Rinkeby testnet: [ 0x37465edC8~ ]. The Smartcontract itself is funded with ETH & LINK, which is used to payout winning bets and in exchange for data from Chainlink oracles. The Smartcontract declares the 50% chance in a transparent way, as well as recording each transaction in an immutable decentralized ledger. The betting system is based on a 50% chance equation where a random hash is generated by the Chainlink network to match above or below the halfway mark of possible hashes.

Declaring 50% chance, (0.5*(uint256+1))

uint256 constant half =
    57896044618658097711785492504343953926634992332820282019728792003956564819968;

uint256 (uint is an alias) is a unsigned integer which has:

minimum value of 0
maximum value of 2^256-1 = 115792089237316195423570985008687907853269984665640564
039457584007913129639935 //78 decimal digits

Send rewards to the winners

function verdict(uint256 random) public payable onlyVFRC {
    // Check bets from latest betting round, one by one
    for (uint256 i = lastGameId; i < gameId; i++) {
        // Reset winAmount for current user
        uint256 winAmount = 0;

        // If user wins, then receives 2x of their betting amount
        if (
            (random >= half && games[i].bet == 1) ||
            (random < half && games[i].bet == 0)
        ) {
            winAmount = games[i].amount * 2;
            games[i].player.transfer(winAmount);
        }
        emit Result(
            games[i].id,
            games[i].bet,
            games[i].seed,
            games[i].amount,
            games[i].player,
            winAmount,
            random,
            block.timestamp
        );
    }
    // Save current gameId to lastGameId for the next betting round
    lastGameId = gameId;
}

IPFS

TossUp's application files are hosted on the Interplanetary FileSystem (IPFS). Being deployed this way, the application is hosted with peer 2 peer functionality in a completely distributed, decentralized way. TossUp is deployed with and utilizes the fleek platform & CDN for the quickest and most reliable IPFS user experience.

Chainlink

Chainlink is being used to provide randomness, and thus, fairness to the betting platform. Chainlink nodes are also being used as an oracle or reliable source of information related to the live price of ETH and Wei in USD.

Request for randomness

function getRandomNumber(uint256 userProvidedSeed)
    internal
    returns (bytes32 requestId)
{
    require(
        LINK.balanceOf(address(this)) > fee,
        "Error, not enough LINK - fill contract with faucet"
    );
    return requestRandomness(keyHash, fee, userProvidedSeed);
}

Callback function used by VRF Coordinator

function fulfillRandomness(bytes32 requestId, uint256 randomness)
    internal
    override
{
    randomResult = randomness;

    // Send final random value to the verdict();
    verdict(randomResult);
}

Returns latest ETH/USD price from Chainlink oracles

function ethInUsd() public view returns (int256) {
    (
        uint80 roundId,
        int256 price,
        uint256 startedAt,
        uint256 timeStamp,
        uint80 answeredInRound
    ) = ethUsd.latestRoundData();

    return price;
}

/* ethUsd - latest price from Chainlink oracles (ETH in USD * 10**8).
 * weiUsd - USD in Wei, received by dividing:
 *          ETH in Wei (converted to compatibility with etUsd (10**18 * 10**8)),
 *          by ethUsd.
 */
function weiInUsd() public view returns (uint256) {
    int256 ethUsd = ethInUsd();
    int256 weiUsd = 10**26 / ethUsd;

    return uint256(weiUsd);
}

Requirements

node
npm
metamask

Installation

npm i

Usage

npm run start
npm run test a (optional)
browse: localhost:3001/

🌀 Click the image(s) below to view the live webapplication

Web3 Modal

Bet

Setup

Tests

Questions

Contact me at matt@brassey.io with any questions or comments.

License

toss-up is published under the CC0_1.0_Universal license.

The Creative Commons CC0 Public Domain Dedication waives copyright interest in a work you've created and dedicates it to the world-wide public domain. Use CC0 to opt out of copyright entirely and ensure your work has the widest reach. As with the Unlicense and typical software licenses, CC0 disclaims warranties. CC0 is very similar to the Unlicense.