Self-diagnosis approach for key synchronization problem in symmetric crypto systems used in SCADA

SCADA is widely used in critical infrastructures for monitoring and controlling the processes of industrial plants. The communications that occur in SCADA systems are transmission of sensed real time data across various devices, details of activities going on in the devices, information related to breaks and leakages in the system etc. As the numbers of deliberate cyber attacks on these systems are increasing, it is essential to achieve secure communication between the authorized devices. Use of symmetric crypto technique, which is suitable for real time and resource constrained devices, enables the authorized parties to share a common secret key. As these secret keys need to be preshared or updated for confidential communications; enforcing key synchronization in the communicating parties is a major issue. This paper proposes key synchronization mechanisms using self diagnosis approach. The self diagnosis approach using finite state machine enables each device in the system to participate in discovering the device which is not key synchronized, by transiting the detector´s current state to a new one based on local evidences and arriving at accepted state outputs, resulting in the final diagnosis report. This report helps to look for the devices that have key synchronization problem and thus supports for secure and transparent communication in SCADA systems.