function reportBySignature(address user, uint160 root, uint32 index, bytes32 r, bytes32 s, uint8 v) public {
        bytes32 messageHash = keccak256(abi.encodePacked(root, index));
        require(user == ecrecover(messageHash, 27 + v, r, s), "Invalid signature");
        _report(user, root, index);
    }