Blackjack dApp

Blackjack game run on the Ethereum blockchain using web3.js and React web framework.

Planning to put this on mainnet and stake it for some small amount, and see what happens, after thoroughly testing. For now, this project is run locally on a development server at http://127.0.0.1:3000 and the contract is also deployed to Rinkeby.

Getting started

This project and guide are built and tested on an Ubuntu 18.04 virtual machine. I'm using ganache-cli for local Ethereum blockchain deployment and Metamask for wallet management.

Prerequisites

First install required software, node.js and npm, Solidity compiler, Truffle suite, and Ganache if you don't already have these. Git and curl are also required for acquiring software.

sudo add-apt-repository ppa:ethereum/ethereum -y && \
sudo apt update && \
sudo apt install -y solc git curl && \
cd ~ && \
curl -sL https://deb.nodesource.com/setup_10.x -o nodesource_setup.sh && \
sudo bash nodesource_setup.sh && \
sudo apt install -y nodejs && \
sudo npm install -g truffle ganache-cli

Installation

Installing this project involves a git clone and a few npm install commands. For example, this installs the project in the ~/blackjack directory.

mkdir ~/blackjack && \
git clone https://github.com/0x9060/blackjack ~/blackjack && \
cd ~/blackjack && \
npm install && \
cd ~/blackjack/client && \
npm install

I also use the browser wallet, Metamask.

Starting up

First run a local test Ethereum blockchain with ganache-cli. Then connect Metamask to the local blockchain using mnemonic provided by ganache. Then run the following.

cd ~/blackjack && \
truffle compile --all && \
truffle test && \
truffle migrate --reset

Make note of the blackjack contract address. Select a ganache account (separate than the one used for playing) to fund the blackjack contract using the fallback function.

cd ~/blackjack/client && \
npm run start

Connect the player's ganache account to the dApp when prompted via Metamask.

Demo

A is provided in this repo, which includes all the above steps. The 8-minute video starts from scratch on a Ubuntu 18.04 system. Most of the duration are the setup steps, with dApp interaction beginning at the 6:22 mark.

Deployed addresses

Commit d31c917 was published to a contract on Rinkeby at address Etherscan. See deployed_addresses.md for more details.

Game rules

• Single deck

• Shuffle after each hand

• Dealer stands on soft 17

• Double any first two cards

• Double after split

• Split only once

• Can hit split aces

• Blackjack pays 3:2

• Late surrender refunds 1:2

• No Insurance

Contract design

See design_pattern_decisions.md for details on the following:

• Access control and mortality
• Circuit breakers

Contract security

See avoiding_common_attacks.md for details on the following:

• Integer overflow/underflow
• Card reveal scheme
• Deck shuffling randomness

Project structure

This is a truffle project using a React front-end, built from the truffle react box. The project directory is constructed as follows:

.
├── avoiding_common_attacks.md
├── client
│   ├── package.json
│   ├── package-lock.json
│   ├── public
│   │   ├── favicon.ico
│   │   ├── index.html
│   │   ├── manifest.json
│   │   └── robots.txt
│   ├── README.md
│   ├── src
│   │   ├── App.css
│   │   ├── App.js
│   │   ├── App.test.js
│   │   ├── contracts
│   │   │   ├── Blackjack.json
│   │   │   ├── Buffer.json
│   │   │   ├── CBOR.json
│   │   │   ├── Context.json
│   │   │   ├── Migrations.json
│   │   │   ├── OracleAddrResolverI.json
│   │   │   ├── Ownable.json
│   │   │   ├── ProvableI.json
│   │   │   ├── SafeMath.json
│   │   │   ├── solcChecker.json
│   │   │   └── usingProvable.json
│   │   ├── getWeb3.js
│   │   ├── index.css
│   │   ├── index.js
│   │   ├── logo.svg
│   │   └── serviceWorker.js
│   └── yarn.lock
├── contracts
│   ├── Blackjack.sol
│   ├── Migrations.sol
│   └── provableAPI.sol
├── deployed_addresses.md
├── design_pattern_decisions.md
├── LICENSE
├── migrations
│   ├── 1_initial_migration.js
│   └── 2_deploy_contracts.js
├── package.json
├── package-lock.json
├── README.md
├── test
│   ├── blackjack.test.js
│   ├── exceptionsHelpers.js
│   └── TestBlackjack.sol
└── truffle-config.js

TO-DO

High level plans for major changes to project, most not yet started.

• Use oracle for RNG on the fly (e.g., from Wolfram Alfa using provableAPI).
• Provide a gas proxy such that the player only interacts with MetaMask when placing bets (i.e., the house pays the gas for hitting and standing). Should also mitigate risk of leaking information through OOG reverts.
• Implement upgradeability using a proxy contract.
• Separate betting and action functions entirely.
• Fix refunds for dealer Blackjack, other payout quirks - write a lot more payment tests.
• Gas optimization
• General refactoring