anon-voting-demo

Onchain Anonymous Voting demo.

TL;DR: users vote onchain by sending a zk-proof where they prove that they belong to the census without revealing who they are in it.

This project builds on top of OAV circuits, which follows a similar design done in vocdoni/zk-franchise-proof and Semaphore. The census in this project is compatible with OVOTE census, and a similar circuit design but implemented in arkworks can be found at ark-anon-vote.

Target:

• DAOs that are non-token-based
• That want to have anonymous on-chain voting
• Which members are willing to pay gas costs (or DAO refunds it)

Packages

• smartcontracts
• clientlib
• react-ui

Overview

Users send their vote + zk-proof to the smart contract, proving that they belong to the census (without revealing who they are) and that their vote has not been already casted.

The census is build from the public keys of the DAO members.

Each user computes a zk-proof which will be verified onchain. Proof proves:

• They know a privK corresponding to a pubK (without revealing any of both)
• pubK is placed in some CensusTree leaf (without revealing which one) under the CensusRoot (which is set in the contract on process creation)
• privK has signed a hash of the vote+chainID+processID
• signature hashed together with the ProcessId and ChainID leads to the given Nullifier, which the contract ensures that has not already been used, in order to prevent double voting
• vote contains a valid value (either 0 or 1, yes/no)

Circuit (grey background indicates public inputs):

User flow

• User connects wallet and generates their voting key
• User sends their voting key to CensusBuilder
• CensusBuilder builds the census and publishes it to IPFS
• Voting phase
  • User selects the voting process (in which the user is a member of the census)
  • User generates a zk-proof
    • proves that the user belongs in census, without revealing their pubK
  • User sends vote + zkproof to the contract
  • Contract verifies zkproof and counts the vote
• Voting process ends, if enough support tx gets executted

sequenceDiagram
    participant user
    participant census_builder
    participant Eth
    participant IPFS
    
    
    par Census creation phase
        user->>user: gen key
        user->>census_builder: pubKey
        census_builder->>census_builder: build census
        census_builder->>IPFS: publish census
    and Process creation phase
        census_builder->>Eth: new process
        user->>Eth: get process
        Eth-->>user: process.census-ipfs-hash
    and Voting phase
        user->>IPFS: get census by ipfs-hash
        IPFS-->>user: census
        user->>user: generate zk-census-proof
        user->>Eth: vote + zk-census-proof
        Eth->>Eth: verify zk-census-proof & process vote
    end

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