90 research outputs found
An Observational Theory for Mobile Ad Hoc Networks
AbstractWe propose a process calculus to study the observational theory of Mobile Ad Hoc Networks. The operational semantics of our calculus is given both in terms of a Reduction Semantics and in terms of a Labelled Transition Semantics. We prove that the two semantics coincide. The labelled transition system is then used to derive the notions of simulation and bisimulation for ad hoc networks. As a main result, we prove that the (weak) labelled bisimilarity completely characterises (weak) reduction barbed congruence, a standard, branching-time, contextually-defined program equivalence. We then use our (bi)simulation proof methods to formally prove a number of non-trivial properties of ad hoc networks
Equational Reasonings in Wireless Network Gossip Protocols
Gossip protocols have been proposed as a robust and efficient method for
disseminating information throughout large-scale networks. In this paper, we
propose a compositional analysis technique to study formal probabilistic models
of gossip protocols expressed in a simple probabilistic timed process calculus
for wireless sensor networks. We equip the calculus with a simulation theory to
compare probabilistic protocols that have similar behaviour up to a certain
tolerance. The theory is used to prove a number of algebraic laws which
revealed to be very effective to estimate the performances of gossip networks,
with and without communication collisions, and randomised gossip networks. Our
simulation theory is an asymmetric variant of the weak bisimulation metric that
maintains most of the properties of the original definition. However, our
asymmetric version is particularly suitable to reason on protocols in which the
systems under consideration are not approximately equivalent, as in the case of
gossip protocols
Modelling MAC-Layer Communications in Wireless Systems
We present a timed process calculus for modelling wireless networks in which
individual stations broadcast and receive messages; moreover the broadcasts are
subject to collisions. Based on a reduction semantics for the calculus we
define a contextual equivalence to compare the external behaviour of such
wireless networks. Further, we construct an extensional LTS (labelled
transition system) which models the activities of stations that can be directly
observed by the external environment. Standard bisimulations in this LTS
provide a sound proof method for proving systems contextually equivalence. We
illustrate the usefulness of the proof methodology by a series of examples.
Finally we show that this proof method is also complete, for a large class of
systems
A Formal Approach to Cyber-Physical Attacks
We apply formal methods to lay and streamline theoretical foundations to
reason about Cyber-Physical Systems (CPSs) and cyber-physical attacks. We focus
on %a formal treatment of both integrity and DoS attacks to sensors and
actuators of CPSs, and on the timing aspects of these attacks. Our
contributions are threefold: (1) we define a hybrid process calculus to model
both CPSs and cyber-physical attacks; (2) we define a threat model of
cyber-physical attacks and provide the means to assess attack
tolerance/vulnerability with respect to a given attack; (3) we formalise how to
estimate the impact of a successful attack on a CPS and investigate possible
quantifications of the success chances of an attack. We illustrate definitions
and results by means of a non-trivial engineering application
A semantic analysis of key management protocols for wireless sensor networks
Gorrieri and Martinelli's timed Generalized Non-Deducibility on Compositions (tGNDC) schema is a well-known general framework for the formal verification of security protocols in a concurrent scenario. We generalise the tGNDC schema to verify wireless network security protocols. Our generalisation relies on a simple timed broadcasting process calculus whose operational semantics is given in terms of a labelled transition system which is used to derive a standard simulation theory. We apply our tGNDC framework to perform a security analysis of three well-known key management protocols for wireless sensor networks: \u3bcTESLA, LEAP+ and LiSP
A Semantic Theory of the Internet of Things (extended abstract)
We propose a process calculus for modelling and reasoning on systems in the Internet of Things paradigm. Our systems interact both with the physical environment, via sensors and actuators, and with smart devices, via short-range and Internet channels. The calculus is equipped with a standard notion of labelled bisimilarity which represents a fully abstract characterisation of a well-known contextual equivalence. We use our semantic proof-methods to prove run-time properties of a non-trivial case study as well as system equalities
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