Message board with anonymity set inclusion proofs.

On-chain Privacy DApp Demo using inclusion proofs

This demo showcases all the parts needed to create a privacy preserving DApp with good UX which are:

• A circuit
• A smart contract
• A relayer
• A webapp

✅Features

Feature	Supported
Aztec Noir circuit	✅
Solidity verifier	✅
ECDSA verification circuit	✅
Merkle tree membership proof	✅
Prover on browser (WASM)	✅
Ethers.js 6.9 relayer	✅
MIT license	✅

🚀How to launch

Step 1. Generate and deploy the Solidity verifier

Make sure you installed Nargo 0.22.0 as detailed below:

On Linux

mkdir -p $HOME/.nargo/bin && \
curl -o $HOME/.nargo/bin/nargo-x86_64-unknown-linux-gnu.tar.gz -L https://github.com/noir-lang/noir/releases/download/v0.22.0/nargo-x86_64-unknown-linux-gnu.tar.gz && \
tar -xvf $HOME/.nargo/bin/nargo-x86_64-unknown-linux-gnu.tar.gz -C $HOME/.nargo/bin/ && \
echo 'export PATH=$PATH:$HOME/.nargo/bin' >> ~/.bashrc && \
source ~/.bashrc

On MAC

mkdir -p $HOME/.nargo/bin && \
curl -o $HOME/.nargo/bin/nargo-x86_64-apple-darwin.tar.gz -L https://github.com/noir-lang/noir/releases/download/v0.22.0/nargo-x86_64-apple-darwin.tar.gz && \
tar -xvf $HOME/.nargo/bin/nargo-x86_64-apple-darwin.tar.gz -C $HOME/.nargo/bin/ && \
echo '\nexport PATH=$PATH:$HOME/.nargo/bin' >> ~/.zshrc && \
source ~/.zshrc

Now generate the Solidity verifier.

cd circuit
nargo codegen-verifier

This will generate a Solidity file located at circuit/contract/circuit/plonk_vk.sol. Deploy it on an EVM on-chain.

Before you continue

Make sure you generate your anonymity set. Usually you may want to generate them on a library provided by Aztec that has the implementation of Pedersen hashing method that matches their prover library. However that library has not been released yet. So for the sake of compatibility we'll use the following circuit to print the merkle tree.

use dep::std::ecdsa_secp256k1::verify_signature;
use dep::std;
use dep::std::scalar_mul;
use dep::std::hash;

fn main(index : Field,
  leafLeft: Field,
  leafRight: Field
) {
    let root = std::merkle::compute_merkle_root(leafLeft, index, [leafRight]);
    std::println(root);
}

In this example we'll use the following merkle tree with a few ethereum accounts I control. When you generate your own merkle tree make sure to update the sendProof function on the app.js file. And also, when you launch your CommentVerifier contract pass as paramater your merkle root.

└─ 0x2a550743aa7151b3324482a03b2961ec4b038672a701f8ad0051b2c9d2e6c4c0
   ├─ 0x1476e5c502f3a532e7c36640e88eebf769ae99d6c50f3be65279ca937b795a3d
   │  ├─ 0x000000000000000000000000707e55a12557E89915D121932F83dEeEf09E5d70
   │  └─ 0x000000000000000000000000bef34f2FCAe62dC3404c3d01AF65a7784c9c4A19
   └─ 0x00000000000000000000000008966BfFa14A7d0d7751355C84273Bb2eaF20FC3
      └─ 0x00000000000000000000000008966BfFa14A7d0d7751355C84273Bb2eaF20FC3

Step 2. Deploy the verifier contract

Now deploy the CommentVerifier contract located at contracts/CommentVerifier.sol. Pass the Verifier contract you just generated as constructor parameter.

Step 3. Launch the Relayer

Let's launch the relayer first. Fill the .env file based on .env.example on the relayer/ directory and run the following.

cd relayer
npm install
npm start

Setp 4. Launch the webapp and verify a proof

Open a new terminal and launch the webapp. Now fill the .env file based on .env.example on the webapp/, the run the following.

cd webapp
npm install
npm start

The webapp will automatically open on your browser. Now you will be able to generate proofs on your browser and send them to the relayer for on-chain verification.

⚠️Known issues (PRs welcome)

• This demo uses normal wallet signatures hence proofs are not nullifiable. See plume