In addition to the hardening of equipment, communications
channels between devices also need to be secured. Cryptographic
algorithms form a core part of securing communications
in commercial networks, as they provide data confidentiality,
integrity and authentication. The use of conventional
network equipment means that many established technologies
such as the IP Security and Secure Socket Layer protocols
can be used at higher levels. Unfortunately, the nature ofcontrol equipment makes implementation of security features
at lower levels problematic