This paper presents a novel approach to formal modeling and analyzing the resilience of networked sensor and actuator systems against targeted cyber-attacks, leveraging Timed Process Algebra (TPA). Recognizing the critical role of these systems in modern infrastructures and their inherent vulnerabilities, we develop a formal TPA-based model to represent sensors, actuators, communication channels, and malicious intruders as interacting processes. This model captures the dynamic behavior of the network, including data flow, control commands, and timing constraints, enabling the analysis of attack scenarios such as sensor disabling, actuator compromise, and communication disruption. We demonstrate some decidable and undecidable properties regarding the precise modeling of intruders, as well as employ model checking and an equivalence approach to verify some safety properties concerning intruders and supervisors.

Gene regulatory networks represent the interactions among genes regulating the activation of specific cell functionalities and they have been successfully modeled using threshold Boolean networks. In this paper we propose a systematic translation of threshold Boolean networks into reaction systems. Our translation produces a non redundant set of rules with a minimal number of objects. This translation allows us to simulate the behavior of a Boolean network simply by executing the (closed) reaction system we obtain. This can be very useful for investigating the role of different genes simply by “playing” with the rules. We developed a tool able to systematically translate a threshold Boolean network into a reaction system. We use our tool to translate two well known Boolean networks modelling biological systems: the yeast-cell cycle and the SOS response in Escherichia coli. The resulting reaction systems can be used for investigating dynamic causalities among genes.

Reaction systems are a qualitative formalism for modeling systems of biochemical reactions. They describe the evolution of sets of objects representing biochemical molecules. One of the main characteristics of Reaction systems is the non-permanency of the objects, namely objects disappear if not pr oduced by any enabled reaction. Reaction systems execute in an environment that provides new objects at each step. Causality properties of reaction systems can be studied by using notions of formula based predictor. In this context, we define a notion of opacity that can be used to study information flow properties for reaction systems. Objects will be partitioned into high level (invisible) and low level (visible) ones. Opacity ensures that the presence (or absence) of high level objects cannot be guessed observing the low level objects only. Such a property is shown to be decidable and computable by exploiting the algorithms for minimal formula based predictors.

A quantification of process’s security by differential privacy is defined and studied in the framework of probabilistic process algebras. The resulting (quantitative) security properties are investigated and compared with other (qualitative and quantitative) security notions.

Opacity testing is formalized and studied. We specify opacity testers as well as tested systems by (timed) process algebras. We model various testers according to how sophisticated observations of tested system they can make and which kind of conclus

Process testing as a way to obtain information on confidential data is investigated. Our working formalism is based on an appropriate (probabilistic) process algebra and (probabilistic) testing. We define testing noninterference as well as sets of pr

Formalisms for analysis of systems of various nature specified by process algebras are proposed. They allow us to formalize security properties based on an absence of information flow and properties on system's integrity. Resulting properties are com

Different techniques for expressing an amount of information on secrete data which can be obtained by a process observation are presented. They are based on information theory and they express certainty about sets of private actions which execution i

Formalisms for description how much information on private actions can be obtained by observing public ones are presented. Two sets of private actions are considered. The set of actions which execution is guaranteed according to observations and the

A formal model for diagnostics of biological systems modelled as P systems is presented. We assume the presence of some biologically motivated changes (frequently pathological) in the systems behavior and investigate when these changes could be diagnosed by an external observer by exploiting some techniques originally developed for reasoning on system security.

A general framework for defining security properties is presented. It allows us to model many traditional security properties as well as to define new ones. The framework is based on process algebras contexts and processes relations. By appropriate choice of both of them we can model also probabilistic and quantified security properties.

A quantification of process's security by quantification of an amount of information flow is defined and studied in the framework of timed process algebras. The resulting quantified security is compared with other (qualitative) security notions. Unprecise and limited observations are defined and discussed.