Contract Deployment

To add contracts to your application, we'll start by creating a new aztec-nargo project. We'll then compile the contracts, and write a simple script to deploy them to our Sandbox.

info

Follow the instructions here to install aztec-nargo if you haven't done so already.

Initialize Aztec project

Create a new contracts folder, and from there, initialize a new project called token:

mkdir contracts && cd contracts
aztec-nargo new --contract token

Then, open the contracts/token/Nargo.toml configuration file, and add the aztec.nr and value_note libraries as dependencies:

[dependencies]
aztec = { git="https://github.com/AztecProtocol/aztec-packages/", tag="aztec-packages-v0.44.0", directory="noir-projects/aztec-nr/aztec" }
authwit = { git="https://github.com/AztecProtocol/aztec-packages/", tag="aztec-packages-v0.44.0", directory="noir-projects/aztec-nr/authwit"}
compressed_string = {git="https://github.com/AztecProtocol/aztec-packages/", tag="aztec-packages-v0.44.0", directory="noir-projects/aztec-nr/compressed-string"}

Last, copy-paste the code from the Token contract into contracts/token/main.nr:

token_all
mod types;
mod test;

// Minimal token implementation that supports `AuthWit` accounts.
// The auth message follows a similar pattern to the cross-chain message and includes a designated caller.
// The designated caller is ALWAYS used here, and not based on a flag as cross-chain.
// message hash = H([caller, contract, selector, ...args])
// To be read as `caller` calls function at `contract` defined by `selector` with `args`
// Including a nonce in the message hash ensures that the message can only be used once.

contract Token {
    // Libs

    use dep::compressed_string::FieldCompressedString;

    use dep::aztec::{
        hash::compute_secret_hash,
        prelude::{NoteGetterOptions, Map, PublicMutable, SharedImmutable, PrivateSet, AztecAddress},
        encrypted_logs::encrypted_note_emission::{encode_and_encrypt_note, encode_and_encrypt_note_with_keys}
    };

    use dep::authwit::auth::{assert_current_call_valid_authwit, assert_current_call_valid_authwit_public, compute_authwit_nullifier};

    use crate::types::{transparent_note::TransparentNote, token_note::{TokenNote, TOKEN_NOTE_LEN}, balances_map::BalancesMap};

    #[aztec(storage)]
    struct Storage {
        admin: PublicMutable<AztecAddress>,
        minters: Map<AztecAddress, PublicMutable<bool>>,
        balances: BalancesMap<TokenNote>,
        total_supply: PublicMutable<U128>,
        pending_shields: PrivateSet<TransparentNote>,
        public_balances: Map<AztecAddress, PublicMutable<U128>>,
        symbol: SharedImmutable<FieldCompressedString>,
        name: SharedImmutable<FieldCompressedString>,
        decimals: SharedImmutable<u8>,
    }

    #[aztec(public)]
    #[aztec(initializer)]
    fn constructor(admin: AztecAddress, name: str<31>, symbol: str<31>, decimals: u8) {
        assert(!admin.is_zero(), "invalid admin");
        storage.admin.write(admin);
        storage.minters.at(admin).write(true);
        storage.name.initialize(FieldCompressedString::from_string(name));
        storage.symbol.initialize(FieldCompressedString::from_string(symbol));
        storage.decimals.initialize(decimals);
    }

    #[aztec(public)]
    fn set_admin(new_admin: AztecAddress) {
        assert(storage.admin.read().eq(context.msg_sender()), "caller is not admin");
        storage.admin.write(new_admin);
    }

    #[aztec(public)]
    #[aztec(view)]
    fn public_get_name() -> pub FieldCompressedString {
        storage.name.read_public()
    }

    #[aztec(private)]
    #[aztec(view)]
    fn private_get_name() -> pub FieldCompressedString {
        storage.name.read_private()
    }

    #[aztec(public)]
    #[aztec(view)]
    fn public_get_symbol() -> pub FieldCompressedString {
        storage.symbol.read_public()
    }

    #[aztec(private)]
    #[aztec(view)]
    fn private_get_symbol() -> pub FieldCompressedString {
        storage.symbol.read_private()
    }

    #[aztec(public)]
    #[aztec(view)]
    fn public_get_decimals() -> pub u8 {
        storage.decimals.read_public()
    }

    #[aztec(private)]
    #[aztec(view)]
    fn private_get_decimals() -> pub u8 {
        storage.decimals.read_private()
    }

    #[aztec(public)]
    #[aztec(view)]
    fn admin() -> Field {
        storage.admin.read().to_field()
    }

    #[aztec(public)]
    #[aztec(view)]
    fn is_minter(minter: AztecAddress) -> bool {
        storage.minters.at(minter).read()
    }

    #[aztec(public)]
    #[aztec(view)]
    fn total_supply() -> Field {
        storage.total_supply.read().to_integer()
    }

    #[aztec(public)]
    #[aztec(view)]
    fn balance_of_public(owner: AztecAddress) -> Field {
        storage.public_balances.at(owner).read().to_integer()
    }

    #[aztec(public)]
    fn set_minter(minter: AztecAddress, approve: bool) {
        assert(storage.admin.read().eq(context.msg_sender()), "caller is not admin");
        storage.minters.at(minter).write(approve);
    }

    #[aztec(public)]
    fn mint_public(to: AztecAddress, amount: Field) {
        assert(storage.minters.at(context.msg_sender()).read(), "caller is not minter");
        let amount = U128::from_integer(amount);
        let new_balance = storage.public_balances.at(to).read().add(amount);
        let supply = storage.total_supply.read().add(amount);

        storage.public_balances.at(to).write(new_balance);
        storage.total_supply.write(supply);
    }

    #[aztec(public)]
    fn mint_private(amount: Field, secret_hash: Field) {
        assert(storage.minters.at(context.msg_sender()).read(), "caller is not minter");
        let pending_shields = storage.pending_shields;
        let mut note = TransparentNote::new(amount, secret_hash);
        let supply = storage.total_supply.read().add(U128::from_integer(amount));

        storage.total_supply.write(supply);
        pending_shields.insert_from_public(&mut note);
    }

    // TODO: Nuke this - test functions do not belong to token contract!
    #[aztec(private)]
    fn privately_mint_private_note(amount: Field) {
        let caller = context.msg_sender();
        storage.balances.add(caller, U128::from_integer(amount)).emit(encode_and_encrypt_note(&mut context, caller, caller));

        Token::at(context.this_address()).assert_minter_and_mint(context.msg_sender(), amount).enqueue(&mut context);
    }

    #[aztec(public)]
    #[aztec(internal)]
    fn assert_minter_and_mint(minter: AztecAddress, amount: Field) {
        assert(storage.minters.at(minter).read(), "caller is not minter");
        let supply = storage.total_supply.read() + U128::from_integer(amount);
        storage.total_supply.write(supply);
    }

    #[aztec(public)]
    fn shield(from: AztecAddress, amount: Field, secret_hash: Field, nonce: Field) {
        if (!from.eq(context.msg_sender())) {
            // The redeem is only spendable once, so we need to ensure that you cannot insert multiple shields from the same message.
            assert_current_call_valid_authwit_public(&mut context, from);
        } else {
            assert(nonce == 0, "invalid nonce");
        }

        let amount = U128::from_integer(amount);
        let from_balance = storage.public_balances.at(from).read().sub(amount);

        let pending_shields = storage.pending_shields;
        let mut note = TransparentNote::new(amount.to_field(), secret_hash);

        storage.public_balances.at(from).write(from_balance);
        pending_shields.insert_from_public(&mut note);
    }

    #[aztec(public)]
    fn transfer_public(from: AztecAddress, to: AztecAddress, amount: Field, nonce: Field) {
        if (!from.eq(context.msg_sender())) {
            assert_current_call_valid_authwit_public(&mut context, from);
        } else {
            assert(nonce == 0, "invalid nonce");
        }

        let amount = U128::from_integer(amount);
        let from_balance = storage.public_balances.at(from).read().sub(amount);
        storage.public_balances.at(from).write(from_balance);

        let to_balance = storage.public_balances.at(to).read().add(amount);
        storage.public_balances.at(to).write(to_balance);
    }

    #[aztec(public)]
    fn burn_public(from: AztecAddress, amount: Field, nonce: Field) {
        if (!from.eq(context.msg_sender())) {
            assert_current_call_valid_authwit_public(&mut context, from);
        } else {
            assert(nonce == 0, "invalid nonce");
        }

        let amount = U128::from_integer(amount);
        let from_balance = storage.public_balances.at(from).read().sub(amount);
        storage.public_balances.at(from).write(from_balance);

        let new_supply = storage.total_supply.read().sub(amount);
        storage.total_supply.write(new_supply);
    }

    #[aztec(private)]
    fn redeem_shield(to: AztecAddress, amount: Field, secret: Field) {
        let pending_shields = storage.pending_shields;
        let secret_hash = compute_secret_hash(secret);
        // Get 1 note (set_limit(1)) which has amount stored in field with index 0 (select(0, amount)) and secret_hash
        // stored in field with index 1 (select(1, secret_hash)).
        let mut options = NoteGetterOptions::new();
        options = options.select(TransparentNote::properties().amount, amount, Option::none()).select(
            TransparentNote::properties().secret_hash,
            secret_hash,
            Option::none()
        ).set_limit(1);
        let notes = pending_shields.get_notes(options);
        let note = notes.get_unchecked(0);
        // Remove the note from the pending shields set
        pending_shields.remove(note);

        // Add the token note to user's balances set
        // Note: Using context.msg_sender() as a sender below makes this incompatible with escrows because we send
        // outgoing logs to that address and to send outgoing logs you need to get a hold of ovsk_m.
        let from = context.msg_sender();
        storage.balances.add(to, U128::from_integer(amount)).emit(encode_and_encrypt_note(&mut context, from, to));
    }

    #[aztec(private)]
    fn unshield(from: AztecAddress, to: AztecAddress, amount: Field, nonce: Field) {
        if (!from.eq(context.msg_sender())) {
            assert_current_call_valid_authwit(&mut context, from);
        } else {
            assert(nonce == 0, "invalid nonce");
        }

        storage.balances.sub(from, U128::from_integer(amount)).emit(encode_and_encrypt_note(&mut context, from, from));

        Token::at(context.this_address())._increase_public_balance(to, amount).enqueue(&mut context);
    }

    #[aztec(private)]
    fn transfer(to: AztecAddress, amount: Field) {
        let from = context.msg_sender();

        // By fetching the keys here, we can avoid doing an extra read from the storage, since from_ovpk would
        // be needed twice.
        let header = context.get_header();
        let from_ovpk = header.get_ovpk_m(&mut context, from);
        let from_ivpk = header.get_ivpk_m(&mut context, from);
        let to_ivpk = header.get_ivpk_m(&mut context, to);

        let amount = U128::from_integer(amount);
        storage.balances.sub(from, amount).emit(encode_and_encrypt_note_with_keys(&mut context, from_ovpk, from_ivpk));
        storage.balances.add(to, amount).emit(encode_and_encrypt_note_with_keys(&mut context, from_ovpk, to_ivpk));
    }

    /**
     * Cancel a private authentication witness.
     * @param inner_hash The inner hash of the authwit to cancel.
     */
    #[aztec(private)]
    fn cancel_authwit(inner_hash: Field) {
        let on_behalf_of = context.msg_sender();
        let nullifier = compute_authwit_nullifier(on_behalf_of, inner_hash);
        context.push_new_nullifier(nullifier, 0);
    }

    #[aztec(private)]
    fn transfer_from(from: AztecAddress, to: AztecAddress, amount: Field, nonce: Field) {
        if (!from.eq(context.msg_sender())) {
            assert_current_call_valid_authwit(&mut context, from);
        } else {
            assert(nonce == 0, "invalid nonce");
        }

        // By fetching the keys here, we can avoid doing an extra read from the storage, since from_ovpk would
        // be needed twice.
        let header = context.get_header();
        let from_ovpk = header.get_ovpk_m(&mut context, from);
        let from_ivpk = header.get_ivpk_m(&mut context, from);
        let to_ivpk = header.get_ivpk_m(&mut context, to);

        let amount = U128::from_integer(amount);
        storage.balances.sub(from, amount).emit(encode_and_encrypt_note_with_keys(&mut context, from_ovpk, from_ivpk));
        storage.balances.add(to, amount).emit(encode_and_encrypt_note_with_keys(&mut context, from_ovpk, to_ivpk));
    }

    #[aztec(private)]
    fn burn(from: AztecAddress, amount: Field, nonce: Field) {
        if (!from.eq(context.msg_sender())) {
            assert_current_call_valid_authwit(&mut context, from);
        } else {
            assert(nonce == 0, "invalid nonce");
        }

        storage.balances.sub(from, U128::from_integer(amount)).emit(encode_and_encrypt_note(&mut context, from, from));

        Token::at(context.this_address())._reduce_total_supply(amount).enqueue(&mut context);
    }

    /// Internal ///

    #[aztec(public)]
    #[aztec(internal)]
    fn _increase_public_balance(to: AztecAddress, amount: Field) {
        let new_balance = storage.public_balances.at(to).read().add(U128::from_integer(amount));
        storage.public_balances.at(to).write(new_balance);
    }

    #[aztec(public)]
    #[aztec(internal)]
    fn _reduce_total_supply(amount: Field) {
        // Only to be called from burn.
        let new_supply = storage.total_supply.read().sub(U128::from_integer(amount));
        storage.total_supply.write(new_supply);
    }

    /// Unconstrained ///

    unconstrained fn balance_of_private(owner: AztecAddress) -> pub Field {
        storage.balances.balance_of(owner).to_field()
    }
}

^{_{Source code: noir-projects/noir-contracts/contracts/token_contract/src/main.nr#L1-L415}}

Helper files

The Token contract also requires some helper files. You can view the files here. Copy the types.nr and the types folder into contracts/token/src.

Compile your contract

We'll now use aztec-nargo to compile.

Now run the following from your contract folder (containing Nargo.toml):

aztec-nargo compile

Deploy your contracts

Let's now write a script for deploying your contracts to the Sandbox. We'll create a Private eXecution Environment (PXE) client, and then use the ContractDeployer class to deploy our contracts, and store the deployment address to a local JSON file.

Create a new file src/deploy.mjs:

// src/deploy.mjs
import { writeFileSync } from 'fs';
import { Contract, loadContractArtifact, createPXEClient } from '@aztec/aztec.js';
import { getInitialTestAccountsWallets } from '@aztec/accounts/testing';
import TokenContractJson from "../contracts/token/target/token_contract-Token.json" assert { type: "json" };


const { PXE_URL = 'http://localhost:8080' } = process.env;

async function main() {
  const pxe = createPXEClient(PXE_URL);
  const [ownerWallet] = await getInitialTestAccountsWallets(pxe);
  const ownerAddress = ownerWallet.getCompleteAddress();

  const TokenContractArtifact = loadContractArtifact(TokenContractJson);
  const token = await Contract.deploy(ownerWallet, TokenContractArtifact, [ownerAddress, 'TokenName', 'TKN', 18])
    .send()
    .deployed();

  console.log(`Token deployed at ${token.address.toString()}`);

  const addresses = { token: token.address.toString() };
  writeFileSync('addresses.json', JSON.stringify(addresses, null, 2));
}

main().catch((err) => {
  console.error(`Error in deployment script: ${err}`);
  process.exit(1);
});

We import the contract artifacts we have generated plus the dependencies we'll need, and then we can deploy the contracts by adding the following code to the src/deploy.mjs file. Here, we are using the ContractDeployer class with the compiled artifact to send a new deployment transaction. The wait method will block execution until the transaction is successfully mined, and return a receipt with the deployed contract address.

Note that the token's _initialize() method expects an owner address to mint an initial set of tokens to. We are using the first account from the Sandbox for this.

info

If you are using the generated typescript classes, you can drop the generic ContractDeployer in favor of using the deploy method of the generated class, which will automatically load the artifact for you and type-check the constructor arguments:

await Token.deploy(client).send().wait();

Run the snippet above as node src/deploy.mjs, and you should see the following output, along with a new addresses.json file in your project root:

Token deployed to 0x2950b0f290422ff86b8ee8b91af4417e1464ddfd9dda26de8af52dac9ea4f869

Next steps

Now that we have our contracts set up, it's time to actually start writing our application that will be interacting with them.

Contract Deployment

Initialize Aztec project​

Helper files​

Compile your contract​

Deploy your contracts​

Next steps​

Initialize Aztec project

Helper files

Compile your contract

Deploy your contracts

Next steps