Sharif Digital Repository

This thesis presents an integrated formal method for modeling and model checking of component based computing systems. Both components and coordination subsystems are modeled by a variant of standard labeled transition systems called record transition systems. A record transition system is a labeled transition system whose transition labels are records. We use records to model the concurrency of input – output operations in the ports of the system. The concurrency of the executions with respect to common transition labels are modeled by standard parallel composition operator and also a new defined operator called join which is analogous to the join operator defined to compose constraint... 

According to increasing computer systems, needs for verification of such systems with respect to desirable properties is critical. Model checking is one of the best methods of verification. Different methods have been proposed for model checking. The most efficient of these methods is automata-theoretic approach. In this approach, formal specification of desirable property, specified by formula in temporal logics, is translated to corresponding automaton. If the system model is expressed as automaton, the problem of model checking is then reduced to a problem of automata-theory. The question is the following. Are all the computations of the corresponding automaton accepted by the automaton... 

Processalgebras,acompositionalmethodofmodelingsystemsandtheirbehavioural features, have been a key instrument in the verification of systems and have strived to completely span a whole spectrum of verification solutions for diverse areas of applications. In this sense, modeling and analysis of the performance metrics in a Mobile Ad hoc Network (MANET) in contrast to other systems, face different challenges which demand different strategies. Hence, our goal here is to model and analyze the qualitative and quantitative aspects of MANETs within one especially designed compositional framework. To achieve this framework, we will first have a look at the different methods which aim to model MANETs... 

Electronic voting refers to voting methods that is done using electronic devices or via the Internet or Web. Helios and Civitas protocols are among the recent protocols introduced in this field. Importance and high sensitivity of electronic voting protocols has led researchers to pay high attention about their security analysis. In recent years, different approaches have been used to inspect and analyze electronic voting protocols. In many of such approaches, analysis had been done in a very abstract environment and without considering the operational requirements.The purpose of this thesis is to evaluate the security features of electronic voting protocols, considering their operational and... 

In this thesis, we first study agent-based systems, and briefly review methods to formally describe such systems. One of these methods is theMetatem language. This language uses a form of linear-time temporal logic to describe the behavior of agents over time. We then introduce modal logics, and argue that they are well suited to describing agents’ knowledge in agent-based systems. We also introduceModal Logic of Knowledge, a combination of linear-time temporal and modal logics, using which temporal behavior of multi agent systems, along with knowledge of agents can be specified.Then, we review and implement a tableau based theorem-proving algorithm for this logic, which can be used as a... 

Nowadays, one of the problems of network designers and users is the correctness of network equipment functionality. Since routers play an important role in information transfer between various networks and communicate with each other through a routing protocol, any violation of such protocol can result in the network's failure or defective transfer of data. Thus, being assured of the conformance of the implemented protocol in a router with what has been defined in the protocol's standard is of great significance. To this end, before using or exposing a router, network equipment testers should run protocol conformance tests on it and insure its correct functionality. This brings up the... 

Routers play a key role in transferring information between various Networks. It is very important to make sure about the compatibility of OSPF in a router with its standard description. In this regard, before presenting or applying a router and also evaluating its performance, it is necessary to carry out conformance test with the help of network equipment testers Tester designers extract test cases from protocol standard description through non-formal ways and exam them on network equipment.
In this thesis, a part of OSFP protocol has been modeled through colored Petri nets. In this regard, two sections of OSPF RFC have been model checked: neighbor state machine and data base... 

Security protocols assure the security of the communications in computer systems using techniques such as cryptographic primitives. However, the usage of such protocols is faced by the lack of fault tolerance, where a minor disruption could cause a destructive damage. Therefore, there is a requirement to assess the reliability of these protocols. In this thesis model checking of timed security protocols is done. Model checking process includes steps that will be modeling protocol with high level and human readable specification language named THLPSL and converting this specification to special kind of timed automata named XTA and model checking will be done with UPPAAL verification tool. We... 

Today's modern industrial control systems (ICS) and SCADA infrastructures, use industrial networks to communicate with the sensors and actuators installed in the field. In recent years the increase in use of standard protocols in this networks, and also the connection of industrial networks to the internet introduced new challenges in the area of industrial network security. The difference in the property, size, and requirements of this networks in comparison to legacy computer networks have made the legacy security solutions such as firewalls and IDS to not have enough efficiency. Some researches work on implementing new solution to meet the requirements of industrial networks in the area... 

The problem of spacecraft attitude determination (AD) using thermal data is investigated. Given the Solar space environment, the key dominant mechanism of heat transfer will be radiation, in which the Sun and Earth are the major contributing heat sources that affect the satellite external surface temperatures. In this sense, the net heat fluxes (NHF) of a satellite surface that is insulated against any internal heat communication will only be related to these main radiating sources. In order to utilize the satellite temperature data for AD, a heat attitude model (HAM) that relates the satellite surfaces NHF to its attitude is developed using three orthogonal satellite surfaces. Assuming... 

In this thesis we study non-parametric estimation of constrained bivariate probability density functions and discuss its applications in model construction of dynamical systems and their safety verification. In many industrial applications, it is essential to obtain an estimator for density functions that satisfy particular constraints. If additional information about distribution of a random variable is known in form of moment constraints, the kernel density estimator can be obtained by replacing uniform weights with the generalized empirical likelihood estimators.Our results indicate that the constructed kernel density estimator provides an improved approximation. Moreover, due to the... 

In this study, the flexural behavior of simple concrete beams with rectangular section (depth 20cm and width 18 cm) reinforced with perforated steel plates is evaluated. Perforated steel plates are used as an alternative for steel bars in the tension region. Because of special geometry, these plates are more integrated with surrounding concrete as compared with steel rebars. The holes in the plates caused local confinement on the surrounding concrete. Concrete beams are modeled with different number of perforated steel plates (one or two or four layer) in Abaqus software. Also beams with different patch lengths are modeled to evaluate patch length of perforated steel plates. Results of... 

Increasing the complexity of software systems, their ubiquitous presence in the human activities, and necessity to preserving the functional and nonfunctional requirements of the systems under an uncertain environment, increase the need for self-adaptive systems. A self-adaptive system changes its structure and behaviors in response to changes in its environment and the system itself. A key research challenge in the self-adaptive community is to guarantee that the system fulfills its requirements. This issue can be addressed by employing formal methods during the design of the software systems. However, the assurance techniques should be used during the execution of the system as well as the...