zkFold: Ethereum integration library

Integration of zkFold Symbolic smart contracts with the Ethereum blockchain. The repository contains

• user documentation for zkFold Symbolic circuits;
• the smart contracts specification;
• the off-chain code for transaction building;
• end-to-end tests for the zkFold Symbolic smart contracts.

User documentation for zkFold Symbolic circuits

The user documentation contains the necessary information about the development of ZK smart contracts using zkFold Symbolic in application to the Ethereum blockchain.

What is zkFold Symbolic?

zkFold Symbolic is a subset of Haskell compilable to arithmetic circuits. It is, therefore, a high-level functional programming language that allows developers to harness the power of zero knowledge protocols for their trustless, decentralized, and privacy-preserving applications. It aims to reduce the barrier to entry in the development of zk-enhanced applications and smart contracts.

Write your own circuit

1. Read the documentation on writing zkFold Symbolic circuits.
2. Write your own circuit with zkFold Symbolic (or import one of the examples). (Ethereum support is in progress)

The smart contracts specification

• Core Ethereum smart contract
• ZK-powered token standard

Core Ethereum smart contract

The Core smart contract which is a plonk verifier with pre built setup, created via the gnark. Also called a Verifier contract.

Core verifier contract API:

• Verify: verify your proof and public_inputs;

ZK-powered token standard

zkFold Symbolic smart contract can be verified on-chain using a ZK verifier contract. Currently, we provide token contract Symbolic. Namely, Symbolic verifier contract verifies the statement with the public input derived from the state of the contract as well as transaction data.

You can find the Symbolic verifier specification here. Below is the snippet of the Solidity script for the Symbolic verifier contract:

Symbolic verifier contract API:

• deposit: deposits funds to the contract;
• withdraw: withdraws funds from the contract;
• newTransfer: create transfer with circuit;
• batchTransfer: performs batch transfer to accounts.

Off-chain code for transaction building

• circuit: create circuit example;
• setup: create setup from circuit;
• solidity: create a Verifier from setup;
• prover: prove the setup.

Building the project

For Haskell backend

This project can be built with Cabal 3.10.2.1 and GHC 9.6.3.

cabal build

For Go backend

go build

For JS backend

npx hardhat node

Deploy a zkFold Symbolic smart contract on Ethereum

1. Choose a suitable on-chain verifier Symbolic.
2. Compile the circuit and write it to a file with compileIO.
3. Create a Verifier contract with setup.
4. Post the Verifier smart contract on Ethereum.
5. Post the zkFold Symbolic smart contract on Ethereum.
6. Сalculate the batch transfer.
7. Claim your rewards.