MACI Christmas Voting

A simple dAPP built using MACI (Minimal Anti Collusion Infrastructure) - use it to vote on your christmas movie selection with your team.

After all, don't we all deserve a little bit of privacy, and fun?

Instructions

1. Clone the MACI repository on branch v1

git clone https://github.com/privacy-scaling-explorations/maci.git -b v1

2. Setup up the repo

npm install && npm run bootstrap && npm run build

Make sure you install the additional required tools (you can find them on the README.md file)

3. Setup hardhat

Within the contracts package, edit the hardhat.config.js file:

/**
 * @type import('hardhat/config').HardhatUserConfig
 */
require('@nomiclabs/hardhat-ethers')
require('dotenv').config()

const {
  DEFAULT_ETH_SK,
  DEFAULT_ETH_PROVIDER,
} = require('./build/defaults')

const config = {
  defaultNetwork: 'arbitrum_goerli',
  networks: {
    localhost: {
      url: process.env.ETH_PROVIDER || DEFAULT_ETH_PROVIDER,
      accounts: [ process.env.ETH_SK || DEFAULT_ETH_SK ],
      loggingEnabled: false,
    },
    arbitrum_goerli: {
      url: String(process.env.ETH_PROVIDER_ARB),
      accounts: [ String(process.env.ETH_SK_ARB) ],
      loggingEnabled: true,
    }
  },
  paths: {
    sources: "../contracts/contracts/",
    artifacts: "../contracts/artifacts"
  }
};

module.exports = config;

In this example we setup arbitrum_goerli as network. Additionally, crate an .env file with the following (amend names are required to fit the hardhat config file):

ETH_SK_ARB=
ETH_PROVIDER_ARB=

3. Create or download the proving keys (Coordinator)

You can download the zkeys from here:

https://github.com/privacy-scaling-explorations/maci/wiki/Download-Precompiled-Circuit-and-Zkeys

Or generate your own using zkey-manager by running the following inside the cli package:

npx zkey-manager genZkeys -c ./zkeys.config.yml

4. Generate coordinator's key pair (Coordinator)

Run node build/index.js genMaciKeypair inside the cli package and take note of those. They will be required to create a poll (the public key) and the private key to decrypt the messages and generate the tally/proofs

4. Deploy and configure the required contracts (Coordinator)

For a detailed explaination of what the cli flags mean, please refer to this guide

• node build/index.js deployVkRegistry - To deploy the VkRegistry contract
• node build/index.js setVerifyingKeys -s 10 -i 1 -m 2 -v 2 -b 1 -p ./zkeys/ProcessMessages_10-2-1-2_test.0.zkey -t ./zkeys/TallyVotes_10-1-2_test.0.zkey - To set the verifying keys on the VkRegistry smart contract
• node build/index.js create - To deploy the rest of the contracts such as the Poseidon hasher implementations and MACI. Please note that this will deploy a version of MACI that allows anyone to signup and that assigns a constant voice credit balance (100 VC). Should you wish to gatekeep signups, a signup gatekeeper such as SignUpTokenGatekeerp and corresponding SignUpToken should be deployed instead.
• node build/index.js deployPoll -p $COORDINATOR_MACI_PUB_KEY -t 360 -g 25 -mv 25 -i 1 -m 2 -b 1 -v 2 - This deploys a new Poll with a duration of 1 hour

If you did not take notes of the deployed contract addresses, you can find them inside the file cli/contractAddress.txt.

5. Setup and run the API (Coordinator)

The example API is a simple REST API that uses express and talks to a mariadb database. Create a database with the name of your choosing and the following table:

CREATE TABLE movies (
    id INT PRIMARY KEY AUTO_INCREMENT,
    title VARCHAR(255),
    url TEXT,
    imageUrl TEXT
);

Now you can set the .env file with the database name, and the connection details for mariadb.

# Server
PORT=8000
# DB
DB_ADDRESS=
DB_PORT=
DB_USERNAME=
DB_PASSWORD=
DB_NAME=

Finally, run the API using yarn start

6. Setup and run the frontend (Coordinator)

Note You will need to move the maci-domainobjs and maci-crypto packages from the MACI repo to the node_modules directory (you can find them under the cli package).

Now that we deployed everything and have the contracts addresses (in particular MACI and the deployed Poll), we can setup the frontend.

Crate an .env file from the .env-template file provided inside the frontend folder and fill with the MACI and Poll contract addresses.

REACT_APP_MACI=$MACI_CONTRACT_ADDRESS
REACT_APP_POLL=$MACI_POLL_ADDRESS
REACT_APP_API_URL=$API_URL

To run the frontend first install the dependencies and then run:

yarn install 
yarn start

The frontend will bind to all intefaces (0.0.0.0)

7. Use the frontend (Anyone)

The app requires an user to be connected with their wallet on the arbitrum testnet (feel free to change this).

You will be able to fill a form to add a movie choice, generate a MACI key pair (which you should make note of as it is needed to send a message), signup to MACI, and vote.

8. Merge the merkle trees (Coordinator)

Once the poll has finished, the coordinator should merge the trees with the following cli commands:

node build/index.js mergeSignups --poll-id $POLL_ID 
node build/index.js mergeMessages --poll-id $POLL_ID

9. Generate the proofs (Coordinator)

For faster generation, you can input the transaction hash of the MACI's contract deployment.

Here you will need the coordinator's private key.

node build/index.js genProofs 
    -sk $COORDINATOR_MACI_PRIVATE_KEY \
    -o $POLL_ID \
    -t tally.json \
    -f proofs.json \
    -r ~/rapidsnark/build/prover \
    -wp ./zkeys/ProcessMessages_10-2-1-2_test \
    -wt ./zkeys/TallyVotes_10-1-2_test \
    -zp ./zkeys/ProcessMessages_10-2-1-2_test.0.zkey \
    -zt ./zkeys/TallyVotes_10-1-2_test.0.zkey \

10. Prove on chain (Coordinator)

To verify the proof on chain, please run the following:

node build/index.js proveOnChain \
    -o $POLL_ID \
    -q $POLL_PROCESSOR_AND_TALLYER_CONTRACT_ADDRESS \
    -f $PROOFS_DIRECTORY

11. Verify the tally (Anyone)

You can use the cli to verify the tally on-chain

node build/index.js verify \
    --contract $MACI_CONTRACT \
    --poll-id $POLL_ID \
    --tally-file $TALLY_FILE_PATH \
    --ppt $POLL_PROCESSOR_AND_TALLYER_CONTRACT_ADDRESS