Security considerations for FAN-Internet connections

The interconnection between field area networks and IP-based LANs, as well as the Internet as a whole, is becoming increasingly popular. Emerging security issues have been neglected or underrated in the past. However, traditional security concepts that work well for LANs and the Internet are hardly applicable to field bus systems. Based on an example from home automation, we review the problem and consider ways to prevent attacks both from the outside world and from within the field bus. Particular emphasis is given to firewalls, which are found to be only of limited value for securing field bus-Internet gateways. To tackle the security problem both on the field bus level and on the Internet, we propose the use of smart cards for authentication and encryption. We discuss modifications that are necessary to make field bus nodes secure, why smart cards are "different" and strategies to implement access control on the gateway.