SAT and SMT-Based Verification of Security Protocols Including Time Aspects

For many years various types of devices equipped with sensors have guaranteed proper work in a huge amount of machines and systems. For the proper operation of sensors, devices, and complex systems, we need secure communication. Security protocols (SP) in this case, guarantee the achievement of security goals. However, the design of SP is not an easy process. Sometimes SP cannot realise their security goals because of errors in their constructions and need to be investigated and verified in the case of their correctness. Now SP uses often time primitives due to the necessity of security dependence on the passing of time. In this work, we propose and investigate the SAT-and SMT-based formal verification methods of SP used in communication between devices equipped with sensors. For this, we use a formal model based on networks of communicating timed automata. Using this, we show how the security property of SP dedicated to the sensors world can be verified. In our work, we investigate such timed properties as delays in the network and lifetimes. The delay in the network is the lower time constraint related to sending the message. Lifetime is an upper constraint related to the validity of the timestamps generated for the transmitted messages.

Observer Patterns for Timed Properties

Dwyer et al. proposed qualitative specification patterns that enable the practitioners of model checking tools to write formal specifications mainly used for automatic model checking. Although this involves formalisms that are not always easy to handle by engineers, to facilitate the integration of formal methods based on these definition patterns in the industrial field, several formal techniques and languages have been proposed. This paper studies a domain specific language named CDL which help non-experts writing formal specifications effortlessly. In CDL, a property is transformed into an observer automaton to perform a reachability analysis. The existing CDL patterns allow non-experts to reason about occurrence and order of events, but not enough about their timing. Furthermore, the semantics of patterns and transformations are not ideally formalized and are still complex. This work serves to extend the existing CDL system by patterns related to time. The contribution is illustrated in an industrial embedded system.

Optimal enforcement of (timed) properties with uncontrollable events

This paper deals with runtime enforcement of untimed and timed properties with uncontrollable events. Runtime enforcement consists in defining and using mechanisms that modify the executions of a running system to ensure their correctness with respect to a desired property. We introduce a framework that takes as input any regular (timed) property described by a deterministic automaton over an alphabet of events, with some of these events being uncontrollable. An uncontrollable event cannot be delayed nor intercepted by an enforcement mechanism. Enforcement mechanisms should satisfy important properties, namely soundness, compliance and optimality – meaning that enforcement mechanisms should output as soon as possible correct executions that are as close as possible to the input execution. We define the conditions for a property to be enforceable with uncontrollable events. Moreover, we synthesise sound, compliant and optimal descriptions of runtime enforcement mechanisms at two levels of abstraction to facilitate their design and implementation.