Deploying Noir app on Ztarknet

This is a step by step tutorial showing how to deploy a toy privacy preserving app on Ztarknet.
We will use Noir for writing ZK circuit, Garaga toolchain to generate Cairo contract, and sncast to interact with the chain.

Set up the environment

Installation

Install Starknet development suite (recommended way is via asdf):

• Scarb https://docs.swmansion.com/scarb/download.html#install-via-asdf
• Starknet Foundry https://foundry-rs.github.io/starknet-foundry/getting-started/installation.html

Create and deploy your account

make account-create

Go to the faucet and top up your account address.

make account-deploy

Make sure you received the funds:

make account-balance

Deploy application

Installation

Install Noir development toolchain:

make install-noir
make install-barretenberg

Install Garaga SDK & CLI:

pip install garaga==0.18.1

Note

Python 3.10 is required to install Garaga. Use pyenv to manage your Python versions.

Create and prove a circuit

Start with creating a new Noir project:

nargo new circuit
cd circuit
nargo check

Fill the Prover.toml file with the inputs:

x = "1"
y = "2"

Execute the circuit to generate a witness:

nargo execute witness

Prove the circuit:

bb prove --scheme ultra_honk --zk --oracle_hash starknet -b ./target/circuit.json -w ./target/witness.gz -o ./target

Generate a verifying key:

bb write_vk --scheme ultra_honk --oracle_hash starknet -b ./target/circuit.json -o ./target

Generate and verifier contract

Let Garaga automatically generate a Scarb project for you:

garaga gen --system ultra_starknet_zk_honk --vk ./circuit/target/vk --project-name verifier

Now we can build the contract:

scarb build

Deploy verifier contract

First we need to declare the contract ("upload it's code hash to the network"):

# In the root dir
cd verifier && sncast declare --contract-name UltraStarknetZKHonkVerifier

Then we can instantiate it (change class-hash according to the output on the previous step):

# In the root dir
sncast invoke \
  --contract-address 0x041a78e741e5af2fec34b695679bc6891742439f7afb8484ecd7766661ad02bf \
  --function "deployContract" \
  --calldata 0x3575239fa10a4e2bacbf0e2105f8d86473aa19d21441b39675be7fbb5924adf 0x0 0x0 0x0

Check the transaction in the explorer to see the deployed contract address (see events).

What just happened:

• We asked universal deployer contract (UDC v1) to deploy Garaga verifier
• We passed verifier class hash as a first argument and set the rest to zeros (no constructor parameters)

Verify the proof on Ztarknet

Serialize Noir proof as contract calldata:

garaga calldata --system ultra_starknet_zk_honk --proof circuit/target/proof --vk circuit/target/vk --public-inputs circuit/target/public_inputs > calldata.txt

Let's first call the verifier contract (without creating a transaction):

sncast call \
    --contract-address 0x02048def58e122c910f80619ebab076b0ef5513550d38afdfdf2d8a1710fa7c6 \
    --function "verify_ultra_starknet_zk_honk_proof" \
    --calldata $(cat calldata.txt)

Now let's invoke the verifier contract:

sncast invoke \
  --contract-address 0x02048def58e122c910f80619ebab076b0ef5513550d38afdfdf2d8a1710fa7c6 \
  --function "verify_ultra_starknet_zk_honk_proof" \
  --calldata $(cat calldata.txt)

Check the transaction in the explorer.

Get help

Something got wrong?

Ask us in the Zypherpunk hackathon chat.