Information-Flow Attacks Based on Limited Observations

Two formal models for description of timing attacks are presented, studied and compared with other security concepts. The models are based on a timed process algebra and on a concept of observations which make visible only a part of a system behaviour. An intruder tries to deduce some private system activities from this partial information which contains also timing of actions. To obtain realistic security characterizations some limitations on observational power of the intruder are applied. It is assumed that the intruder has only limited time window to perform the attack or time of action occurrences can be measured only with a given limited precision.