Proof of USDC

You can use an email from Coinbase that contains Congrats! You received USDC rewards to generate a ZK proof that you hold USDC on Coinbase.

This ZK proof can be used to mint an NFT corresponding to your reward amount in the ProofOfUSDC contract.

Running locally

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, the main circuit being coinbase.circom. CoinbaseVerifier circuit use EmailVerifier circuit from @zk-email/circuits.

The regex circuit required to parse/extract USDC reward amount can be generated using https://github.com/zkemail/zk-regex package.

» Generate Coinbase Regex Circuit

# CWD = packages/circuits
yarn generate-regex

This will generate components/reward_amount_regex.circom using the config in components/reward_amount.json. This reward_amount_regex.circom is imported in coinbase.circom.

Note that reward_amount_regex.circom is already in repo, so this step is optional.

» Build the circuit

# CWD = packages/circuits
yarn build

This will create coinbase.wasm and other files in packages/circuits/build directory.

You can test the circuit using

# CWD = packages/circuits
yarn test

» 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.

To upload to S3, the below script can be used.

python3 upload_to_s3.py --build-dir <project-path>/proof-of-usdc/packages/circuits/build --circuit-name coinbase

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

» Generate Input and Proof

# CWD = packages/circuits/scripts
ts-node generate-proof.ts --email-file ../tests/emls/coinbase-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. The main contract is ProofOfUSDC.sol.

You can build the contracts using

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

Run tests

# CWD = packages/contracts
yarn test

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/TestCoinbase.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).

Deployment Process

1. Compile the .circom contracts into wasm and r1cs
   • CWD: packages/circuits
   • yarn build
2. Generate a proving key and verification key.
   • CWD: packages/circuits/scripts
   • yarn ts-node dev-setup.ts
3. Deploy verifier contract
   • CWD: packages/contracts
   • PRIVATE_KEY=<pk-hex> forge script script/DeployCoinbase.s.sol:Deploy --rpc-url https://rpc2.sepolia.org --broadcast
4. Upload build files to AWS S3
   • CWD: packages/circuits/scripts
   • python3 upload_to_s3.py
5. Generate a proof on AWS
   • CWD: packages/circuits/scripts
   • ts-node generate-proof.ts --email-file ../tests/emls/coinbase-test.eml --ethereum-address <your-eth-address>
6. Download the proof from AWS S3, and verify it on-chain
   • Call _mint in the ProofOfUSDC contract

Currently deployed contracts on Sepolia:

  Deployed Verifier at address: 0xF068589BA6Eb05be6db861F7c3517099E2a62FC9
  Deployed DKIMRegistry at address: 0x4570f2c537C285859F61C6e5619EAf5Ab81C806f
  Deployed ProofOfUSDC at address: 0xaC60F7C6F55dCCbFc9c9149f69805A88F5Adf3ed

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 ProofOfUSDC 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/

History

This repo was originally part of the zk-email-verify. Please refer there for the commit history and original contributors.