wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

Security in Industrial Communication Systems 22-15
from the device is tunneled through. To secure the tunneling connection, TLS is used. OpenVPN provides
several methods to ensure authentication: a pre-shared symmetric key, a username and password
combination, a TLS certificate, or a combination of these methods. While IPsec manipulates the network
protocol, OpenVPN encapsulates the encrypted VPN packets into untouched TCP or UDP packets
of the host network. However, the VPN packets themselves are secured down to the IP layer (layer 3) in
the routing mode or down to Ethernet (layer 2) in the bridging mode.
22.5.4 Security in Wireless Communication Systems
Like many other sectors, wireless networks are also more and more introduced in industrial and building
automation infrastructures. Main concern is the robustness to electromagnetic interference and in
general the security goal of availability that can only be solved by proper organizational measures (e.g.,
redundant transmission paths). Also, the wireless transmission is prone to eavesdropping and message
insertion since the media can be accessed by everyone. Chapter 28 introduces the security measures to
fulfill the above-mentioned security goals. To combine existing physical security measures (e.g., fences,
closed rooms) to increase security, new research is going in the direction of location-based security
services limiting the accessibility of a network not only by the signal strength, but also by an active
localization of the node. The Austrian Academy of Sciences investigates such security measures based
on a localization of COTS Wireless LAN hardware via dedicated access points [TR2].
22.6 Outlook and Conclusion
The lack of state-of-the-art security measures at the field level of many industrial communication systems
almost solely allows implementing security measures on top of the automation networks. This
usually introduces overhead and undermines interoperability. To omit security is related to high risks.
At the intranet/Internet zone, a general awareness of these risks exists and security measures are commonly
implemented in terms of secured tunneling. At the field-level zone, this awareness is missing.
Looking at threats to industrial communication systems, omitting security measures at the field level
must be very carefully considered. Security measures (at all levels) also help to tackle other problems
such as accidental errors within remote maintenance or safety issues. Therefore, it is worth the effort to
integrate security measures at all levels. Yet, security must not solely be equated to network security or
cryptography. Many security threats, e.g. DoS attacks, require more organizational measures and show
that security must include the complete system and not only a dedicated part. Setting the appropriate
boundaries for security is the most critical part in security design: Defining what is trusted and what
is untrusted requires deep insight into the overall applications, especially since industrial communication
and industrial process control strongly interact with its environment. In practical implementations
the security goals of integrity, availability, and authentication/authorization are the most important
ones to protect. Confidentiality and non-repudiation are of minor interest for industrial applications.
Additionally, traceability is important during maintenance.
Abbreviations
AES
BACnet
CMAC
CIM
CPU
DMZ
DES
DoS
Advanced encryption standard (cryptographic cipher)
Building automation control network
Cipher-based message authentication code
Computer-integrated manufacturing
Central processing unit
Demilitarized zone
Data Encryption Standard (cryptographic cipher)
Denial of service (attack)
© 2011 by Taylor and Francis Group, LLC