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Masa SBT ZKP

A template for creating new SBTs inheriting from the Masa SBT smart contracts, using ZKP.

We use eth-crypto package to encrypt and decrypt the data.

Install dependencies and deployment​

Preparations​

  • Set DEPLOYER_PRIVATE_KEY to the deployers private key in .env.{network}.secret
  • Set INFURA_API_KEY to the Infura API key in .env
  • Set COINMARKETCAP_API_KEY to the CoinMarketCap API key in .env, if needed
  • Set ETHERSCAN_API_KEY to the Etherscan API key in .env, if needed
  • Set the environment variables in every .env.{network} file. These variables are used to deploy the smart contracts to the network.

Install dependencies​

Run:

yarn install

Build smart contracts​

Run:

yarn build

Deploy​

Run:

yarn deploy --network {network}

Contract Deployments​

Deployment addresses​

You can see the deployment address of the smart contracts in the deployments/goerli and deployments/mainnet folders. For every deployed smart contract you will find a <smart_contract>.json JSON file with the address in the "address" field.

Zero-Knowledge Proof​

Zero-knowledge proof is a method by which one party (the prover) can prove to another party (the verifier) that the prover knows a value x that fulfills some constraints without revealing any information apart from the fact that he/she knows the value x.

Circom and dependencies setup​

Install Rust​

curl --proto '=https' --tlsv1.2 https://sh.rustup.rs -sSf | sh

Build Circom from source​

git clone https://github.com/iden3/circom.git
cd circom
cargo build --release
cargo install --path circom

Install snarkjs​

npm install -g snarkjs

Compile the circuit​

cd circuits
circom verifyCreditScore.circom --r1cs --wasm --sym --c

Run circuit trusted setup​

Powers of tau, which is independent of the circuit:

snarkjs powersoftau new bn128 12 pot12_0000.ptau -v
snarkjs powersoftau contribute pot12_0000.ptau pot12_0001.ptau --name="First contribution" -v

Phase 2, which depends on the circuit:

snarkjs powersoftau prepare phase2 pot12_0001.ptau pot12_final.ptau -v
snarkjs groth16 setup verifyCreditScore.r1cs pot12_final.ptau verifyCreditScore_0000.zkey
snarkjs zkey contribute verifyCreditScore_0000.zkey verifyCreditScore_0001.zkey --name="1st Contributor Name" -v
snarkjs zkey export verificationkey verifyCreditScore_0001.zkey verification_key.json

Compute the witness​

Add the input in the file input.json file:

{
  "root": "0x20630d227f9c346b4c6f52a21a4085fb061d8b9eba3ed155b6061ae6d177b693",
  "owner": "0x14B2Bab4d1068e742BAf05F908D7b5A00773B0dd",
  "threshold": 40,
  "operator": 4,
  "value": 45,
  "data": ["0x14B2Bab4d1068e742BAf05F908D7b5A00773B0dd", 45, 3100, 1675196581804]
}

Then execute:

node verifyCreditScore_js/generate_witness.js verifyCreditScore_js/verifyCreditScore.wasm input.json witness.wtns

Generate a proof​

Generate a zk-proof associated to the circuit and the witness:

snarkjs groth16 prove verifyCreditScore_0001.zkey witness.wtns proof.json public.json

Verifying a Proof​

To verify the proof, execute the following command:

snarkjs groth16 verify verification_key.json public.json proof.json

Verifying from a Smart Contract​

We need to generate the Solidity code using the command:

snarkjs zkey export solidityverifier verifyCreditScore_0001.zkey ../contracts/verifier.sol

The Verifier has a view function called verifyProof that returns TRUE if and only if the proof and the inputs are valid. To facilitate the call, you can use snarkJS to generate the parameters of the call by typing:

snarkjs generatecall