Merkle Tree Attestation

             root
            /    \
         n01     n23
        /   \   /   \
       h0   h1 h2   h2  ← h2 is repeated

{
  "record": { "index": 0, "hash": "f651a7c3...", ... },
  "proof": [
    { "sibling": "a3f9b2c1...", "position": "right" },
    { "sibling": "7e2d4a8f...", "position": "right" }
  ],
  "root": "d5c6e7f8..."
}

import hashlib

def verify_proof(record_hash: str, proof: list, claimed_root: str) -> bool:
    current = bytes.fromhex(record_hash)
    
    for step in proof:
        sibling = bytes.fromhex(step['sibling'])
        if step['position'] == 'left':
            # sibling is on the left: hash(sibling + current)
            combined = sibling + current
        else:
            # sibling is on the right: hash(current + sibling)
            combined = current + sibling
        current = hashlib.sha256(combined).digest()
    
    return current.hex() == claimed_root

import { createHash } from 'node:crypto';

function verifyProof(
  recordHash: string,
  proof: { sibling: string; position: 'left' | 'right' }[],
  claimedRoot: string,
): boolean {
  let current = Buffer.from(recordHash, 'hex');

  for (const { sibling, position } of proof) {
    const siblingBuf = Buffer.from(sibling, 'hex');
    const combined =
      position === 'left'
        ? Buffer.concat([siblingBuf, current])
        : Buffer.concat([current, siblingBuf]);
    current = createHash('sha256').update(combined).digest();
  }

  return current.toString('hex') === claimedRoot;
}