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 of
control equipment makes implementation of security features
at lower levels problematic. Industrial equipment generally
has a much longer life cycle than that found in corporate
networks, and has much higher reliability requirements. As
such, the technologies used in industrial networking equipment
are generally mature and proven at the time of installation -
by the end of the equipment’s life-cycle it may be several
generations older than the latest technology [41].