INDEPENDENT VERIFICATION

Verify on-chain anchors without trusting anyone

You don't need ChainMemory's API to verify that a project state was anchored at a specific block. This page shows how to verify directly against the blockchain using standard Web3 tools.

What you need

• The project's state hash (from the API or shared by someone)
• The transaction hash or block number of the anchor
• Node.js with ethers installed — or any Web3 library

Step 1 — Get the anchor data

Use ChainMemory's public (no auth) endpoint or get it from whoever shared the proof:

bash
curl https://api.chainmemory.ai/v1/project/chainmemory/state/anchor

Response
{
  "project": "chainmemory",
  "projectId": "0x77f7d980...",
  "version": 8,
  "state_hash": "0xa6c45d1db753b1ec96240d169b2d91fb0ce76112558b302a8822b2988aeb8212",
  "anchor": {
    "status": "anchored",
    "onchain_anchor_id": 8,
    "tx_hash": "0x95b732d20b8935a2...",
    "block_number": 173831,
    "contract": "0xa7A8BA51950255b3e223a6745597C67009Fe7875"
  },
  "verify": "ProjectStateAnchor.getStateAnchor(projectId, version)"
}

Step 2 — Verify on-chain with Ethers.js

Connect directly to the ChainMemory RPC and read the smart contract. No API key, no account, no trust required.

javascript
import { ethers } from 'ethers';

// Connect to ChainMemory RPC — no API key needed
const provider = new ethers.JsonRpcProvider('https://rpc.chainmemory.ai');

// ProjectStateAnchor contract
const CONTRACT = '0xa7A8BA51950255b3e223a6745597C67009Fe7875';
const ABI = [
  'function getStateAnchor(bytes32 projectId, uint64 version) view returns (bytes32 stateHash, uint256 anchoredAt, address anchoredBy, uint256 anchorId)'
];

const contract = new ethers.Contract(CONTRACT, ABI, provider);

// The project ID is the keccak256 of the project name
const projectId = ethers.keccak256(ethers.toUtf8Bytes('chainmemory'));
const version = 8;

// Read directly from the blockchain
const [stateHash, anchoredAt, anchoredBy, anchorId] = await contract.getStateAnchor(projectId, version);

console.log('On-chain state hash:', stateHash);
console.log('Anchor ID:', anchorId.toString());
console.log('Anchored at:', new Date(Number(anchoredAt) * 1000).toISOString());

// Compare with the hash you received
const expectedHash = '0xa6c45d1db753b1ec96240d169b2d91fb0ce76112558b302a8822b2988aeb8212';
if (stateHash === expectedHash) {
  console.log('VERIFIED — state matches on-chain anchor');
} else {
  console.log('MISMATCH — state has been tampered with');
}

javascript
const Web3 = require('web3');

const web3 = new Web3('https://rpc.chainmemory.ai');

const CONTRACT = '0xa7A8BA51950255b3e223a6745597C67009Fe7875';
const ABI = [{
  name: 'getStateAnchor',
  type: 'function',
  stateMutability: 'view',
  inputs: [
    { name: 'projectId', type: 'bytes32' },
    { name: 'version', type: 'uint64' }
  ],
  outputs: [
    { name: 'stateHash', type: 'bytes32' },
    { name: 'anchoredAt', type: 'uint256' },
    { name: 'anchoredBy', type: 'address' },
    { name: 'anchorId', type: 'uint256' }
  ]
}];

const contract = new web3.eth.Contract(ABI, CONTRACT);

const projectId = web3.utils.keccak256('chainmemory');

const result = await contract.methods.getStateAnchor(projectId, 8).call();
console.log('On-chain state hash:', result.stateHash);
console.log('Anchor ID:', result.anchorId);

Step 3 — Verify the transaction

You can also verify the raw transaction that created the anchor:

javascript
// Read the transaction directly
const tx = await provider.getTransaction('0x95b732d20b8935a286869d90e60a40f5c31d350a94e27bfd7845770fe0c3e2c3');
console.log('From:', tx.from);       // Should be a known validator
console.log('To:', tx.to);           // Should be the contract address
console.log('Block:', tx.blockNumber);

// Read the block to confirm timestamp
const block = await provider.getBlock(tx.blockNumber);
console.log('Block time:', new Date(block.timestamp * 1000).toISOString());