ZK Comments

We are presenting you a DApp built based on Scroll, where Employee can self-attest themselves using the emails they received by providers like Github recently using Zero-knowledge libraries without disclosing anything but the recipient's domain.

How it works

1. Request a forget password request from Github
2. Copy the Original Email received by Github
3. Paste to our website and generate the zk proof on client-side (NO DATA is transferred to server/blockchain at this stage)
4. After the generation of zk proof, type the comments of the company and get it sent to the chain. (Only your email domain, wallet address, public key of the DNS record and comments will be disclosed)

Running locally

Pre-requisites

1. rust
2. foundry
3. zk-regexp

Install dependencies

yarn

Start the web app. In packages/app directory, run

yarn start

This will start the UI at http://localhost:3000/ where you can paste the email, generate proof and mint the NFT.

The UI works against the generated zkeys downloaded from AWS and the deployed contract on Sepolia.

Manual Proof Generation

If you want to generate the proof locally outside browser, follow the instructions below.

Circuits

Circom circuits are located in packages/circuits.

» Generate Regex Circuit

# CWD = packages/circuits
yarn generate-regex:to-address
yarn generate-regex

This will generate src/twitter-reset-regex.circom and src/to-address-regex.circom using the config in src/twitter_reset.json and src/to-domain.json

Note that twitter_reset-regex.circom and to-domain-regex.circom is already in repo, so this step is optional.

» Build the circuit

# CWD = packages/circuits
yarn build:company && yarn build:twitter

This will create twitter.wasm, company.wasm and other files in packages/circuits/build directory.

You can test the circuit using

# CWD = packages/circuits
yarn test:company && yarn test:twitter

» Generating Zkey

You can generate proving and verification keys using

# CWD = packages/circuits/scripts
ZKEY_ENTROPY=<random-number> ZKEY_BEACON=<random-hex> ts-node dev-setup.ts

This will generate zkey files, vkey.json in build directory, and Solidity verifier in packages/contracts/src/Verifier.sol (You might need to manually update the solidity pragma version).

Note: We are using a custom fork of snarkjs which generated chunked zkeys. Chunked zkeys make it easier to use in browser, especially since we have large circuit. You can switch to regular snarkjs in package.json if you don't want to use chunked zkeys.

For browser use, the script also compresses the chunked zkeys.

**The compressed zkeys, vkey, wasm are copied to /build/artifacts` directory. This directory can be served using a local server or uploaded to S3 for use in the browser.

There are helper functions in @zk-email/helpers package to download and decompress the zkeys in the browser.

To use locally, please run cd packages/circuits/build/artifacts && python3 server-cors.py 8080 and the artifacts will be accessible.

» Generate Input and Proof

# CWD = packages/circuits/scripts
# ts-node generate-proof.ts --email-file ../tests/emls/-test.eml --ethereum-address <your-eth-address>

This will generate input + witness using the given email file and Ethereum address, and prove using the generated zkey.

The script will save inputs.json, input.wtns, proof.json, and public.json in proof directory.

The script also verify the generated proof are correct. You can use the proof and public inputs to verify in the Solidity verifier as well.

Contracts

The solidity contracts can be found in packages/contracts.

You can build the contracts using

# CWD = packages/contracts
yarn build  # Assume you have foundry installed

Run tests

# CWD = packages/contracts
yarn test:company

Note that the tests will not pass if you have generated your own zkeys and Verifier.sol as you would have used a different Entropy.

To fix, update the publicSignals and proof in test/TestCompany.t.sol with the values from input.json and public.json generated from the above steps. (Remember that you need to flip items in the nested array of pi_b).

Deploy contracts

# CWD = packages/contracts
PRIVATE_KEY=<pk-hex> forge script script/DeployCompany.s.sol.bak:Deploy -vvvv --rpc-url  https://sepolia-rpc.scroll.io/ --broadcast --legacy --extra-output-files=abi --verifier-url https://api-sepolia.scrollscan.com/api --etherscan-api-key <API-KEY> --verify

They are deployed to scroll sepolia testnet at the following addresses:

src/Verifier.sol 0x19aB947b5bddBf66419415c7b72dc7299BFA7b3A (verified)
src/DKIMRegistry.sol 0x9e58681a270D28a0E26E01d4c1e5942CEA8A984B (verified)
src/ProofOfCompany.sol 0xF9D45eBbD284F0732b2f3826a67f58154738a3FE (failed to verify)

UI

If you want to update the UI based on your own zkeys and contracts, please make the below changes:

• Set the VITE_CONTRACT_ADDRESS in packages/app/.env. This is the address of the ProofOfCompany contract.
• Set VITE_CIRCUIT_ARTIFACTS_URL in packages/app/.env to the URL of the directory containing circuit artifacts (compressed partial zkeys, wasm, verifier, etc). You can run a local server in circuits/build/artifacts directory and use that URL or upload to S3 (or similar) and use that public URL/

Credit

https://github.com/zkemail https://github.com/ethereum-attestation-service