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.

Fetching the Proof

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

Curl

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"
  }
}'

Javascript

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();

• chainId: 11155111 (Sepolia).

• txHash: The tx-hash that emitted the Transfer Event on Sepolia: tx-example.

• 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 > 7016956

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

References

1. Receipt proof request script