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Quick Start

The Quick Start guide will walk you through two core use cases of Hashi: verifying storage proofs or event proofs against a block header and pushing messages across chains. We’ll go through the core use cases with three examples:

verify a foreign event
read a foreign state via storage proofs
push a message to foreign chain.

The code can be found in. This repository serves as a template for developers to kickstart a Hashi project using Hardhat/Foundry.

Verifying foreign event

This example demonstrates the validation of a Transfer Event from an ERC-20 contract on the Sepolia network using an event proof on the Chiado network. The proof is retrieved via an API call and provided to a custom contract to be deployed on Chiado. The contract utilizes the HashiProver helper library to verify the proof against the latest block header recorded in Hashi.

Setting the scene

What we have:

A ERC20 Transfer Event emitted in Sepolia USDC contract.

What we need:

The verification on Chiado

Getting the Event Proof

The first step is to fetch the Event Proof from Sepolia. An important parameter is the block number which ensures that Hashi can verify the proof against the block header stored on Chiado. This is possible if the block header related the emitted event on the origin chain (Sepolia in this case) has already been propagated to the target chain (Chiado in this case). To check the block propagation status is possible to use the .

Fetching the Proof

Use the following curl command to fetch the account and storage proof for the following ERC20 Transaction : .

Validating your statements

Once the proof has been fetched, we can verify it using a custom contract on Chiado. The contract will use the HashiProver helper library to check the proof against the block header stored on Chiado.

Deploying the Custom Verification Contract on Chiado

Here is a custom contract that deployed on Chiado can be used to read and verify the Transfer event on Sepolia:

Deployment:

HashiProver & ShoyuBashi are already deployed on a that can be called from the custom verification contract (this contract). In order to configure a custom oracle set for it is possible to deploy a new ShoyuBashi contract, inherit HashiProver contract and configure your oracle set in the ShoyuBashi contract.
In this example, pass to the custom verification contract constructor <ShoyuBashi contract address on Chiado, the ERC20 contract address on Sepolia, from which the Transfer event is emitted, chain ID of the ERC20Contract (Sepolia: 11155111)>

verifyForeignEvent explanation:

Inputs:

expectedRlpEncodedEvent : an bytes encoded format with the Event information: check out the in order to generate it starting from the Event topics and data.
proof: the HashiAPI retreived proof

Logic:

check that the proof chainID matches the origin chain chainId (Sepolia in this case).
The verifyForeignEvent function validates the event proof against the block header stored on Chiado, which was relayed from Sepolia.
check that rlpEncodedEvent returned from

Check verifyForeignEvent implementation .

Submitting the Proof

Once the contract is deployed on Chiado, you can submit the proof fetched from the API using the following command:

This will trigger the contract to verify the proof using the block header stored in Hashi from Sepolia. If the proof is valid, the rplEncodedEvent will be emitted.

References

Reading foreign state

This example demonstrates the verification of the total supply of USDC on Optimism from Gnosis Chain using a storage proof. The proof will be fetched via HashiAPI and fed to a contract deployed on Gnosis Chain. The contract will use HashiProver to validate the proof against the last Optimism reported block header stored in Hashi.

Setting the scene

What we have:

------

What we need:

The verification on Gnosis Chain chain of USDC total supply on Optimism.

How Hashi enables the Event verification:

Getting the Storage Proof

First we need to fetch the storage proof from Optimism using the block number of a Optimism block which header that has already been propagated to Hashi. This block number ensures that Hashi can verify the proof against the just mentioned block header propagated to Gnosis Chain.

Fetching the Proof

Use the following curl command or javascript script to fetch the account and storage proof for the USDC total supply on Optimism:

chainId: 10 (Optimism).
address: The address of the USDC contract on Optimism: 0x0b2c639c533813f4aa9d7837caf62653d097ff85.
storageKeys: The storage key for the USDC total supply: 0xb.

This curl command returns the account and storage proof for the USDC total supply, which will be used for verification on Gnosis Chain.

Use the SP1 storage proof generator

Hashi support .

Validating your statements

Once the proof has been fetched, we can now verify it using a custom contract on Gnosis Chain. The contract will use the HashiProver helper library to check the proof against the block header stored on Gnosis Chain.

Deploying the custom Verification Contract on Gnosis Chain

Here is a contract that deployed on Gnosis Chain can be used to read and verify the USDC total supply on Optimism:

Deployment:

Pushing a message

In this example, we’ll send a message from a contract on Sepolia to another contract on Chiado, using Hashi to relay and execute the message. The callback will be triggered and validated on Chiado using the provided onMessage function.

Writing your message sending contract

Here’s how you write a contract on Sepolia that dispatches a message using Hashi’s Yaho contract. This message will be relayed to Chiado and trigger the callback.

Explanation:

The contract interacts with the Yaho contract on Sepolia to dispatch a message to Chiado using dispatchMessageToAdapters.
The sendMessageToChiado function takes the target chain ID(10200 for Chiado), target address (ChiadoReceiver contract on Chiado), and the message to be sent.
The reporters, adapters, and threshold are passed into the Yaho contract for cross-chain message validation and relaying.

Deployment:

Deploy this contract on Sepolia, passing the reporters, adapters, and threshold into the constructor.
A list of reporters and adapters contract can be found in:
Yaho contract address can be found in

Implementing your callback

Now, we’ll write the callback function on Chiado using the onMessage implementation you provided. This contract will handle the message sent from Sepolia.

Explanation:

The onMessage function implements the callback, which is triggered when the Yaru contract on Chiado relays the message.
The function checks that the Yaru contract on Chiado is the sender, that the chainId, sender address, and threshold match what was expected, and that the list of adapters matches the expected hash.
After the validations pass, the message is decoded and stored in the contract.

Deployment:

Deploy this contract on Chiado. Ensure that the values like SOURCE_SENDER_ADDRESS (Sepolia sender contract), EXPECTED_THRESHOLD, and ADAPTERS are correctly configured.
Yaru address with respect to the source chain can be found in
A list of adapters on the target chain can be found in

Waiting for the cross-chain execution

Here’s what happens after you send the message:

Message Dispatch on Sepolia:
- When sendMessageToChiado is called on the SepoliaSender contract, the message is dispatched through Yaho on Sepolia.

Validating your statements

Deploying the Custom Verification Contract on Chiado

Here is a custom contract that deployed on Chiado can be used to read and verify the Transfer event on Sepolia:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import { HashiProver } from "./HashiProver.sol";

contract MockERC20Prover {

    event TransferEventVerified(uint256 indexed chainID, bytes rlpEncodedEvent);

    HashiProver public hashiProver;
    address public erc20Contract;
    uint256 public chainID;

    constructor(address shoyuBashi_, address erc20Contract_, uint256 chainID_) {
        hashiProver = HashiProver(shoyuBashi_);
        erc20Contract = erc20Contract_;
        chainID = chainID_;
    }

    function verifyTransferEvent(HashiProver.ReceiptProof calldata proof, bytes memory expectedRlpEncodedEvent) external {
        require(proof.chainId == chainID, "Invalid chain id"); 

        bytes memory rlpEncodedEvent = hashiProver.verifyForeignEvent(proof);

        require(keccak256(rlpEncodedEvent) == keccak256(expectedRlpEncodedEvent), "invalid event");
        emit TransferEventVerified(proof.chainId , rlpEncodedEvent);

        // TODO: Define custom logic here

    }
}

Deployment:

HashiProver & ShoyuBashi are already deployed on a that can be called from the custom verification contract (this contract). In order to configure a custom oracle set for it is possible to deploy a new ShoyuBashi contract, inherit HashiProver contract and configure your oracle set in the ShoyuBashi contract.
In this example, pass to the custom verification contract constructor <ShoyuBashi contract address on Chiado, the ERC20 contract address on Sepolia, from which the Transfer event is emitted, chain ID of the ERC20Contract (Sepolia: 11155111)>

verifyForeignEvent explanation:

Inputs:

expectedRlpEncodedEvent : an bytes encoded format with the Event information: check out the in order to generate it starting from the Event topics and data.
proof: the HashiAPI retreived proof

Logic:

check that the proof chainID matches the origin chain chainId (Sepolia in this case).
The verifyForeignEvent function validates the event proof against the block header stored on Chiado, which was relayed from Sepolia.
check that rlpEncodedEvent returned from

Check verifyForeignEvent implementation .

Submitting the Proof

Once the contract is deployed on Chiado, you can submit the proof fetched from the API using the following command:

This will trigger the contract to verify the proof using the block header stored in Hashi from Sepolia. If the proof is valid, the rplEncodedEvent will be emitted.

References

Implementing your callback

Now, we’ll write the callback function on Chiado using the onMessage implementation you provided. This contract will handle the message sent from Sepolia.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract ChiadoReceiver {
    /// @dev Yaru contract on the Chiado w.r.t the Sepolia
    address public YARU = 0xBA9165973963a6E5608f03b9648c34A737E48f68;  
    /// @dev Source chain ID of Sepolia
    uint256 public SOURCE_CHAIN_ID = 11155111;
    /// @dev Expected threshold to be met by the adapters
    uint256 public EXPECTED_THRESHOLD;
    /// @dev Sender SepoliaSender contract address
    address public SOURCE_SENDER_ADDRESS;
    /// @dev hash of adapters address 
    bytes32 public ADAPTERS_HASH;
    /// @dev message that is last received from sender contract's sendMessageToTarget function
    string public lastReceivedMessage;
    

    constructor(uint256 expectedThreshold, address sourceSender, address[] memory adapters){
        EXPECTED_THRESHOLD = expectedThreshold;
        SOURCE_SENDER_ADDRESS = sourceSender;
        ADAPTERS_HASH = keccak256(abi.encodePacked(adapters));
    }

    /// @dev Function that gets triggered when the message is relayed, called by Yaru contract
    /// @param chainId chainId of the chain where message is sending from
    /// @param sender sender contract
    /// @param threshold threshold of the message that should be met by adapters
    /// @param adapters an array of adapters to check the threshold with
    /// @param data abi-encoded message
    /// @return 
    function onMessage(
        uint256, /*messageId*/
        uint256 chainId,
        address sender,
        uint256 threshold,
        address[] memory adapters,
        bytes memory data
    ) external returns (bytes memory) {
        require(msg.sender == YARU, "only called by Yaru");
        require(chainId == SOURCE_CHAIN_ID, "invalid source chain ID");
        require(threshold == EXPECTED_THRESHOLD, "invalid number of threshold");
        require(sender == SOURCE_SENDER_ADDRESS, "invalid sender address from source chain");
        require( keccak256(abi.encodePacked(adapters)) == ADAPTERS_HASH, "invalid adapters hash");
    
        // Decode the message and store it
        (string memory message) = abi.decode(data, (string));
        lastReceivedMessage = message;

        return "";
    }
}

Explanation:

The onMessage function implements the callback, which is triggered when the Yaru contract on Chiado relays the message.
The function checks that the Yaru contract on Chiado is the sender, that the chainId, sender address, and threshold match what was expected, and that the list of adapters matches the expected hash.
After the validations pass, the message is decoded and stored in the contract.

Deployment:

Deploy this contract on Chiado. Ensure that the values like SOURCE_SENDER_ADDRESS (Sepolia sender contract), EXPECTED_THRESHOLD, and ADAPTERS are correctly configured.
Yaru address with respect to the source chain can be found in
A list of adapters on the target chain can be found in

Quick Start

Verifying foreign event

Setting the scene

Getting the Event Proof

Validating your statements

hashtagDeployment:

hashtagReferences

Reading foreign state

Setting the scene

Getting the Storage Proof

hashtagFetching the Proof

hashtagUse the SP1 storage proof generator

Validating your statements

hashtagDeployment:

Pushing a message

Writing your message sending contract

Implementing your callback

Waiting for the cross-chain execution

Getting the Storage Proof

hashtagFetching the Proof

hashtagUse the SP1 storage proof generator

Setting the scene

Validating your statements

hashtagDeployment:

hashtagReferences

Reading foreign state

Quick Start

Getting the Event Proof

Setting the scene

Pushing a message

hashtagReferences

Verifying foreign event

Writing your message sending contract

Implementing your callback

Validating your statements

hashtagDeployment:

Waiting for the cross-chain execution

hashtagExample Scenario

Deployment:

References

Fetching the Proof

Use the SP1 storage proof generator

Deployment:

Fetching the Proof

Use the SP1 storage proof generator

Deployment:

References

References

Deployment:

Example Scenario