Abstract
Drinking fresh water, turning the lights on, travelling
by tram, calling our family, or getting a medical treatment are
usual activities, but the underlying SCADA (Supervisory Control
and Data Acquisition) systems like CIS (Critical Infrastructure
Systems), ICS (Industrial Control Systems) or DCS (Distributed
Control Systems) were always the target of many types of attacks,
endangered the above mentioned simple activities. During the last
decades because of the fast spread of the internet based services
and the continuous technical development these systems become
more vulnerable than ever. Full reconstruction and innovative
changes in older SCADA systems has high cost, and it is not always
rewarding. Communication protocols as Modbus (1979) serve as a
main basis for SCADA systems, so security of Modbus has a major
impact of the security of SCADA systems. Our paper raises and
answers questions about the security of the Modbus RTU protocol.
We focus on the serial Modbus protocol, because in that method
we found many unsolved problems, like lack of authentication of
the participants, lack of secure channel and so on. The aim of this
paper to propose a secure communication alternative for Modbus
RTU @ RS485 wire. The main advantage of the proposed method
is the coexistence with traditional slaves and bus systems and only
software update is necessary
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