Biblio
Embedded systems that communicate with each other over the internet and build up a larger, loosely coupled (hardware) system with an unknown configuration at runtime is often referred to as a cyberphysical system. Many of these systems can become, due to its associated risks during their operation, safety critical. With increased complexity of such systems, the number of configurations can either be infinite or even unknown at design time. Hence, a certification at design time for such systems that documents a safe interaction for all possible configurations of all participants at runtime can become unfeasible. If such systems come together in a new configuration, a mechanism is required that can decide whether or not it is safe for them to interact. Such a mechanism can generally not be part of such systems for the sake of trust. Therefore, we present in the following sections the SEnSE device, short for Secure and Safe Embedded, that tackles these challenges and provides a secure and safe integration of safety-critical embedded systems.
A lot of research in security of cyber physical systems focus on threat models where an attacker can spoof sensor readings by compromising the communication channel. A little focus is given to attacks on physical components. In this paper a method to detect potential attacks on physical components in a Cyber Physical System (CPS) is proposed. Physical attacks are detected through a comparison of noise pattern from sensor measurements to a reference noise pattern. If an adversary has physically modified or replaced a sensor, the proposed method issues an alert indicating that a sensor is probably compromised or is defective. A reference noise pattern is established from the sensor data using a deterministic model. This pattern is referred to as a fingerprint of the corresponding sensor. The fingerprint so derived is used as a reference to identify measured data during the operation of a CPS. Extensive experimentation with ultrasonic level sensors in a realistic water treatment testbed point to the effectiveness of the proposed fingerprinting method in detecting physical attacks.