# How Hashi Works

Hashi is a decentralized protocol that allows secure cross-chain communication. By enabling contracts on one blockchain to interact with contracts on another, Hashi facilitates cross-chain data transfer and execution through message dispatching, storage proofs, and cryptographic verification.

The process involves **sending a message** or **verifying a state** across blockchains, such as **Sepolia** and **Gnosis Chiado**, using a series of contracts and oracles. Let’s break down how this works in practice:

### **Verifying State with Cross-Chain Proofs**

A powerful feature of Hashi is the ability to verify the state of a contract on one chain using **cryptographic proofs** stored on a different chain. Here’s how this works using Sepolia and Chiado as origin and target chains:

1. **Storing Block Headers**:
   * The first step is to relay **block headers** from Sepolia to Chiado.
   * These headers are stored in the **Header Storage** contract on Chiado and contain essential information like the state root, which can be used to validate the state of a Sepolia smart contract.
2. **Requesting a Proof**:
   * Verify the value stored in a specific storage slot of a contract on Sepolia (Chain A).
   * Generate a **Merkle proof** that shows the value of this storage slot on a particular block on Sepolia. This proof includes information from the block header (stored on Chiado) and the Merkle path leading to the value.
3. **Submitting the Proof**:
   * You submit this proof to the **Yaru** contract on **Chiado**. The **Yaru** contract checks the proof against the block header that was previously relayed and stored in the **Header Storage** contract.
   * If the proof is valid, Hashi confirms that the state on Sepolia matches what was proven in the Merkle proof.

In this way, you can **verify contract state** on Sepolia directly from Chiado, without interacting with Sepolia in real-time, using **trustless proofs** and stored block headers.

### **Message Dispatching Across Chains**

1. **Start on Chain A (Sepolia)**:
   * Imagine you have a contract on Sepolia that needs to send a message to a contract on Gnosis Chiado (Chain B).
   * On **Sepolia**, you use Hashi’s **Yaho** contract, which is specifically designed for dispatching messages across chains.
2. **Sending the Message**:
   * Your Sepolia contract calls the **Yaho** contract, instructing it to send a message to the **Yaho** contract on **Chiado**.
   * The message typically contains the target contract address on Chiado and the data you want to send (such as a function call or value).
3. **Relaying the Message**:
   * Once the message is dispatched, it is picked up by Hashi’s **oracle network**. These oracles listen for events on Sepolia, relay the message, and submit it to **Yaho** on Chiado for execution.
   * Multiple oracles are used for redundancy and security, ensuring that the message is properly validated before it’s passed to Chiado.
4. **Receiving and Executing the Message on Chain B (Chiado)**:
   * On **Chiado**, the **Yaho** contract receives the message after the oracles validate the block header and the message’s integrity.
   * Once validated, the **Yaho** contract triggers the appropriate callback function on the target contract (for example, updating the contract state or calling a specific function).

In practice, this allows you to **seamlessly send a message from Sepolia to Chiado**, have it validated by multiple oracles, and executed on the destination chain.


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