ZK Vote Aggregation Example

A basic vote aggregation project using Hardhat, hardhat-circom, and snark-js.

Install

yarn to install dependencies

Build

yarn circom:dev to build deterministic development circuits.

Further, for debugging purposes, you may wish to inspect the intermediate files. This is possible with the --debug flag which the circom:dev task enables by default. You'll find them (by default) in artifacts/circom/

To ensure that the proof is generated correctly, you can verify it with yarn dev:verify-proof.

Tests can be run using yarn test. As convention in Hardhat, the tests will be located in the test folder.

Deployment

To deploy to Goerli network using Infura, first create .env file following the example in .env.example and fill in the two fields.

Then, run npx hardhat run scripts/deploy.js --network goerli to deploy the ZK.sol contract. This will compile the contract and deploy it to the Goerli network. To verify the contract, run npx hardhat verify --network goerli <address>.

Generate Solidity Calldata

To interact with the deployed contract, we need to generate the appropriate calldata to pass into Solidity. To do this, we will perform the steps below.

1. yarn circom:prod
2. yarn witness-calc
3. yarn create-proof
4. yarn verify-proof
5. yarn generate-call

The output of the last command will be the calldata needed for Solidity. Note that the value of b is a 2 x 2 array and will need to be split up into two inputs of 1 x 2 arrays to pass into the Solidity function. Also, note that all values generated are in hex and may need to be converted into decimal before inputing as function arguments.

Todo

1. Rewrite circuit using for loop and var, not just signals.
2. Rewrite ZK.sol for gas savings (less read/write from storage).
3. Test cases
4. Check gas savings compared to without SNARK.