1 A Context Analysis Method for Developing Secure Embedded Naoyasu UbayashiKyushu University, Japan May 22, 2011 SESS’11

Motivation  Security is one of the important issues in developing embedded systems.  Context such as physical phenomena implicitly may become a threat to the embedded systems. Temperature, air pressure, and light may make an alteration of sensed data. This can be considered as an another type of falsification.  It is important to provide a context analysis method for constructing secure embedded systems. 2

Problems to be tackled  It is difficult to decide the boundary of the context that should be taken into account: which context element, an object existing outside of the system, should be included as the targets of requirements analysis. 3 Embedded System Actuator Sensor Contexts Boundary ? Association ? Frame Problem !

Our approach  CAMEmb (Context Analysis Method for Embedded systems) UML Profile for Context Analysis Guide Words for Context Analysis  Only the value-context elements are extracted as the associated context elements because many embedded systems are abstracted as a sensor-and-actuator machine.  Other context elements can be ignored. 4

CAMEmb --- Context analysis using guide words 5 Guide Words for Context Analysis

Context modeling 6 UML profile for context analysis Steps for exploring boundary 1.Context elements (value object) observed or controlled directly by a sensor or an actuator are extracted. 2.Impact factors that affect the states (values) of these context elements are extracted using guide words. Initial Boundary Sensor cannot observe original data Factor related to a specific value Contexts that do not change the values are ignored ! The frame problem is avoided ! Contexts that do not change the values are ignored ! The frame problem is avoided ! Final Boundary Factor that determines the upper limit

Summary  Applying the guide words, we can explore only a sequence of context elements directly or indirectly affecting the data value observed or controlled by the system sensors and actuators.  We can explore the context boundary that guarantees the expected system behavior. 7 Naoyasu Ubayashi, Yasutaka Kamei, Masayuki Hirayama, and Tetsuo Tamai: A Context Analysis Method for Embedded Systems --- Exploring a Requirement Boundary between a System and Its Context, 19th IEEE International Requirements Engineering Conference (RE 2011), to appear.

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