    function updateAccount(string calldata from, string calldata to) external onlyMaster onlyWhenNotStopped
    {
        require(bytes(from).length > 0);
        require(bytes(to).length > 0);
        btc[to] = btc[from];
        eth[to] = eth[from];
        btc[from] = '';
        eth[from] = address(0);
        emit UpdateAddress(from, to);
    }