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tendermint-zk-ibc

Overview

This repository provides TendermintZKLightClient contract, a Solidity implementation of a Zero-Knowledge Proof (ZKP)-based Tendermint light client for IBC. Furthermore, it also provides an IBC relayer support and a ZK prover using Succinct's TendermintX. By utilizing ibc-solidity and these components, we can achieve IBC between EVM chains(e.g. Ethereum mainnet) and Cosmos zones at a practical gas cost.

The following figure shows the high-level architecture of the E2E demo using the components included in this repository. Note that Mock-LC is currently used as IBC Light Client on Tendermint instead of verifying Ethereum consensus. This will soon be replaced by 08-wasm + ethereum-ibc-rs.

Components

TendermintZKLightClient

TendermintZKLightClient is a Solidity contract that implements a ZKP-based light client for Tendermint and ILightClient interface of ibc-solidity. This consists of the following parts:

• ZKP-verifier for header: It verifies a validity proof of header, which is a recursive proof with Groth16/PLONK for TendermintX circuit proof. Note that the trusting period validation and the merkle tree verification for block timestamp and appHash from the header are processed on-chain for now. We will soon improve the circuit to include these verifications.
• State membership/non-membership verifier: A merkle proof verifier implementation optimized for Simple tree and IAVL tree proof specs

Developers can construct their own LightClient contract using a zkp verifier contract according to the verifying key they performed setup and generated.

An example implementation can be found here:

• Groth16
• PLONK

ZKProver

ZKProver is a component that prove validity of given header and provides its proof to the relayer.

This component consists of the following two sub-components:

• plonky2-prover that runs TendermintX circuit to generates proof and prove recursively it using Poseidon BN128 hash
• gnark-verifier that recursively proves the proof from plonky2-prover service utilizing gnark-plonky2-verifier for Groth16/PLONK proof

Relayer

Relayer is a component that requests validity proof of the latest header from ZKProver and calls the updateClient function of the TendermintZKLightClient contract with the proof. This is implemented as prover module of yui-relayer.

Benchmark

The following is the gas report for the TendermintZKLightClient contract. The gas is measured using forge test and the below settings.

Settings:

• Solidity v0.8.24
• optimizer_runs=9999999
• via-ir=true
• evm_version=paris

TODO

• Add misbehaviour support
• Further gas cost optimization
  • Optimize circuit for IBC light client
  • e.g. remove simple tree verification on-chain
• Reduce ZKProver's proving time
• Improve the E2E demo
  • Replace Mock-LC with 08-wasm + ethereum-ibc-rs