# 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 [Hashi Explorer](https://crosschain-alliance.gitbook.io/hashi/meta/explorer).

**Fetching the Proof**

Use the following `curl` command to fetch the **account and storage proof** for the following **ERC20** `Transaction` : [tx-example](https://sepolia.etherscan.io/tx/0x25a6a5c138f3b5a434a3a2b5d6bf7bdf97cb700bd7515f801ecfb71f1d965e7b).

{% tabs %}
{% tab title="Curl" %}

```javascript
curl --location --request POST 'https://jsonrpc.hashi-explorer.xyz/v1' \
--header 'Content-Type: application/json' \
--data-raw '{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "hashi_getReceiptProof",
  "params": {
    "logIndex": 397,
    "blockNumber": 7016999,
    "chainId": 11155111,
    "transactionHash": "0x25a6a5c138f3b5a434a3a2b5d6bf7bdf97cb700bd7515f801ecfb71f1d965e7b"
  }
}'
```

{% endtab %}

{% tab title="Javascript" %}

```python
import axios from "axios";

const main = async () => {
  // fetch event proof from Hashi Prover
  console.log("Fetching event proof from Hashi prover...");
  const result = await axios.post(
    `http://jsonrpc.hashi-explorer.xyz:3000/v1`,
    {
      jsonrpc: "2.0",
      method: "hashi_getReceiptProof",
      params: {
        logIndex: 397,
        blockNumber: 7016999,
        chainId: 11155111,
        transactionHash: "0x25a6a5c138f3b5a434a3a2b5d6bf7bdf97cb700bd7515f801ecfb71f1d965e7b",
      },
      id: 1,
    },
    {
      headers: {
        "Content-Type": "application/json",
      },
    }
  );
  console.log("Event proof result", result.data.result.proof);
};

main();
```

{% endtab %}
{% endtabs %}

* **chainId**: 11155111 (Sepolia).
* **txHash**: The tx-hash that emitted the Transfer Event on **Sepolia**: [tx-example](https://sepolia.etherscan.io/tx/0x25a6a5c138f3b5a434a3a2b5d6bf7bdf97cb700bd7515f801ecfb71f1d965e7b).
* **logIndex**: The log index for the event.
* **blockNumber**: The block number on Sepolia, 7016999, which must have already been propagated to Chiado via Hashi for the proof to be valid. The block number must reference a block that appears after the block containing the event. In this case [7016999](https://sepolia.etherscan.io/block/7016999) > [7016956](https://sepolia.etherscan.io/block/7016956)

This `curl` command / script returns the E**vent Proof** for the `Transfer` **Event** on **Sepolia**, which will be used for verification on **Chiado**.

### References

1. [Receipt proof request script](https://github.com/crosschain-alliance/hashi-template/blob/main/offchain/script/receipt-proof.js)