# 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**:

{% 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_getAccountAndStorageProof",
  "params": {
      "chainId": 10,
      "address": "0x0b2c639c533813f4aa9d7837caf62653d097ff85",
      "storageKeys": ["0x00000000000000000000000000000000000000000000000000000000000000b"],
      "blockNumber": 126086800
  }
}'
```

{% endtab %}

{% tab title="Javascript" %}

```python
import axios from "axios";

const main = async () => {

  // fetch storage proof from Hashi Prover
  console.log("Fetching storage proof from Hashi prover...");
  const result = await axios.post(
    "http://jsonrpc.hashi-explorer.xyz:3000/v1",
    {
      jsonrpc: "2.0",
      method: "hashi_getAccountAndStorageProof",
      params: {
          chainId: 10,
          address: "0x0b2c639c533813f4aa9d7837caf62653d097ff85",
          storageKeys: ["0x00000000000000000000000000000000000000000000000000000000000000b"],
          blockNumber: 126086800
      },
      id: 1,
    },
    {
      headers: {
        "Content-Type": "application/json",
      },
    }
  );
  console.log("Storage proof result", result.data.result.proof);
};

main();
```

{% endtab %}
{% endtabs %}

* **chainId**: 10 (Optimism).
* **address**: The address of the USDC contract on Optimism: `0x0b2c639c533813f4aa9d7837caf62653d097ff85`.
* **storageKeys**: The storage key for the USDC total supply: `0xb`.
* **blockNumber**: The block number on Optimism, **126086800**, which must have already been propagated to **Gnosis Chain** via Hashi for the proof to be valid.

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 [SP1 zkVM to generate storage proofs](https://crosschain-alliance.gitbook.io/hashi/tools/sp1-storage-proof-verifier).

```
RUST_LOG=info cargo run --release -- --execute \
    --rpc-url https://mainnet.infura.io/v3/YOUR-PROJECT-ID \
    --reference-block-number 0x7B60EA3 \
    --proof-block-number 0x783EE90 \
    --account 0x0b2c639c533813f4aa9d7837caf62653d097ff85 \
    --storage-key 0x000000000000000000000000000000000000000000000000000000000000000b
```