Shadow Vote: A private voting bridge

Aztec
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1

Contact Details

Point of Contact: Crisgarner
Telegram @crisgarner

Summary

We propose building a private voting bridge that connects DAO Governor contracts with Aztec. The goal is to enable DAOs to create a proposal on Aztec and allow the execution of code based on the result of the private voting of its delegates. For this proposal, we will focus on the Optimism Testnet.

Start and End Date

Start Date: April 1, 2025

End Date: June 30, 2025

About Us

The team is composed of engineers with ample experience working on DAO governance and private voting.

Crisgarner, former Engineer at PSE, working on MACI (Minimal Anti-Collusion Infrastructure), a privacy-preserving, on-chain voting system. Full-stack developer with over 5 years of experience in Solidity and smart contract development.

Ben Barahona, Full-stack and Blockchain developer with over 5 years of experience in Solidity, and smart contract integrations with mobile, front-end, and back-end applications. Former lead developer for Ballotted, an on-chain voting platform that used smart contracts to create small-scale elections and store encrypted votes on-chain. On top of smart contract development on Ballotted, it also included the development of mobile apps to handle user registration & votes, as well as a CMS to handle election-related actions.

Details

For voting to be truly secure, it must ensure four key properties:

  1. Correct Execution
  2. Censorship Resistance
  3. Privacy
  4. Coercion Resistance.

In today’s DAO landscape, only the first two are typically enforced. The lack of privacy in public voting systems introduces serious challenges, particularly vote coercion and bandwagon effects, where participants are pressured to vote a certain way or simply follow the majority to avoid standing out. This undermines the integrity and independence of governance decisions.

We plan to demo an application that enables a DAO on a Layer 2 to create proposals and allow delegates to vote privately. The proposed architecture includes the following components:

  • A frontend interface for users to interact with the voting system.
  • A Governor contract on L2 that integrates with a relayer.
  • A Relayer contract is a custom bridge that passes the proposal state from Ethereum to Aztec.
  • A private Voting contract on Aztec responsible for recording votes and computing the final tally.

The expected user flow is as follows:

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Coercion resistance is one of the most critical challenges in secure voting. Our focus will be on researching and implementing strategies to mitigate coercion while preserving the other essential properties of secure voting systems.

Grant Milestones and Roadmap

Phase 1: Research & Architecture Design

Conduct in-depth research and finalize the architecture for the private voting bridge. Focus areas include bridging mechanisms, coercion resistance strategies, and integration with Governor-style DAOs.

Phase 2: Smart Contract & Interface Development

Develop the core smart contracts on the L2 (Governor, Bridge/Relayer). Build the base user interface for proposal creation and interaction with the contracts.

Phase 3: Aztec Contract & Integration

Implement the private voting logic on Aztec, including vote casting and tallying. Integrate Aztec contracts with the frontend and connect vote results to the L2 Governor.

Phase 4: Testnet Deployment & Demos

Deploy the complete system on testnet, demonstrating end-to-end flow.

Ongoing Work

  • Continuous testing and UI refinement.
  • Communications with Aztec Team.

Future Work

  • Exploration of deployment on additional L2s.
  • Enhanced privacy and coercion resistance mechanisms.
  • Usability improvements.

An area of our interest beyond the current grant scope is native private voting on Aztec — eliminating the need for DAOs to bridge governance by enabling them to deploy directly on Aztec or run elections entirely.

Grant Amount Requested

US $50,000.

Grant Budget Rationale

This budget covers a dedicated team of 2 engineers working on the project over the course of the proposed roadmap phases.

2

Private voting is a great idea. But if the balances and token holders are on L2 and voting happens on Aztec, what actually do you make private (and how)?

  1. On the public L2, I can see that token holder (0xABC) is voting with 50,000 tokens on this proposal. The token balance/delegated balance at the snapshot is public. So you can’t hide that. You could hide if they are voting for Yes or No but would be great if you could go into detail

  2. when you vote on aztec, how do you do it? is it a commit reveal scheme, in which case each person has to interact twice? Or do you just directly enqueue the call to aztec’s public state in which case the user flow is:
    public l2 - i vote with my publicly known balance → no one sees if I voted yes or no → call Azrec contract privately → it calls aztec contract publicly which holds the talley

So now external user can see that a vote happened on public L2 and can see how much the tally incraesed on Aztec → i.e. doesn’t really save any privacy?

  1. next option is using an FHE coprocessor
  2. you could also use coSNARKs or another mpc scheme.

i think if you could go into detail on how you plan to do privat evoting, what will be private etc, it would be quite nice!

1 Like
3

Thanks for the question — it gets into what we’re exploring.

If governance stays on a L2 (rather than being fully native to Aztec), then balances and delegations at the snapshot remain public. So we can’t hide who is eligible to vote or with how much voting power. What we can make private, however, is how each delegate voted — the direction of the vote (Yes/No/Abstain).

In this initial version, we focus on a commit/reveal scheme within Aztec contracts.

To reach full coercion resistance, we would be inclined to use coSNARKs. We are excited about this direction as it would allow us to create elections that aren’t only for DAOs but any kind of poll that requires complete privacy.

We also talked with a few DAO delegates, and for a pilot, they want privacy in some votes but transparency in others to showcase how they voted.