The security should be baked into the relay aka. whatever you use to translate the data from a IP based protocol to serial data. T-Code is designed to be simpl

The security should be baked into the relay aka. whatever you use to translate the data from a IP based protocol to serial data. T-Code is designed to be simple to understand, implement and decode by micro controllers over a wired connection and those micro controllers often lack the processing power to do cryptographic security. This relies more on physical security.