function validProof(bytes proof, bytes32 root, bytes32 hash) constant returns (bool) {
    bytes32 el;

    for (uint256 i = 32; i <= proof.length; i += 32) {
        assembly {
            el := mload(add(proof, i))
        }

        if (hash < el) {
            hash = sha3(hash, el);
        } else {
            hash = sha3(el, hash);
        }
    }
    return hash == root;
  }